Dr. Jeff Masters' WunderBlog

Large and intensifying Hurricane Alex bears down on northeastern Mexico, South Texas

By: JeffMasters, 02:23 PM GMT del 30 Giugno 2010

Hurricane Alex continues to intensify as it slowly bears down on the coast of northeastern Mexico. Brownsville long-range radar shows the spiral bands of Alex, which has dumped heavy rains of up to four inches in northeastern Mexico and near Brownsville, according to satellite estimates of rainfall. The Brownsville airport received 0.78" of rain in the hour ending at 8am CDT, and 0.61" in the hour ending at 9am CDT. Floods from Alex have already killed ten people--six in Nicaragua, and two each in El Salvador and Guatemala.


Figure 1. Snapshot of the Brownsville long-range radar showing Hurricane Alex approaching the coast.

The 7:12am CDT eye penetration of the Hurricane Hunters found a central pressure of 959 mb, a modest 2 mb drop from the reading four hours previous to that. They noted a very tiny eye, ten miles in diameter, with a gap in the northwest side. Tiny eyes like this tend to be unstable, and in the 9:05am CDT eye penetration, the Hurricane Hunters found that the inner eyewall had collapsed, and the pressure had risen 2 mb, to 961 mb. A new, much larger eye will form today as the day progresses. During these "eyewall replacement cycles", a hurricane will typically weaken a few millibars , and the strongest winds will spread out over a larger area as the hurricane conserves angular momentum. Thus, the hurricane still has about the same amount of destructive power, it is just spread out over a larger area. This tends to increase the hurricane's storm surge, but lessens the wind damage, since the extreme winds of the inner eyewall are no longer present. Satellite loops show a large, well-organized storm with increasing amounts of low-level spiral bands forming, and improving upper-level outflow. Data from last night's flight of the NOAA jet showed an unusually moist atmosphere surrounds Alex, so dry air is no longer a problem for it. It's a good thing Alex has less than a day before making landfall, or else is would be a large and very powerful major hurricane.


Figure 2. Visible light image of Tropical Storm Alex taken at 19:35 UTC (2:35 pm CDT) on June 29, 2010, by NASA's Aqua satellite. At the time, Alex was a tropical storm with 70 mph winds. Image credit: NASA.

Storm Surge
Traditionally, a storm's ranking on the Saffir-Simpson Scale--the familiar Category 1, 2, 3, 4, 5 rankings we always talk about--have also been used to quantify storm surge threat. However, large, weaker storms that cover a huge area of the Gulf of Mexico, like Alex, can generate a larger storm surge than a smaller but more intense hurricane with a higher Saffir-Simpson rating. Thus, the National Hurricane Center has formally discontinued use of the Saffir-Simpson scale to characterize storm surge, and is studying the possibility of issuing separate Storm Surge Warnings a few years from now. These would be in addition to their traditional Hurricane Warnings. To give us a better idea of a storm's surge potential, Dr. Mark Powell of NOAA's Hurricane Research Division has developed the Integrated Kinetic Energy scale to rank storms. The scale ranges from 0 to 6, and a parallel wind damage scale that runs from 0 to 6 is also generated. Alex had an Integrated Kinetic Energy of 2.6 on the 0 to 6 scale at 1:30pm CDT yesterday, and its destructive potential rating for winds was just 1.2. Thus, Alex's surge ranked alomst one-and-a-half categories higher in destructive potential than its wind. These numbers have probably increased by a full category since yesterday afternoon. NHC is giving a 40% - 60% chance of a storm surge of at least 3 feet affecting the Brownsville area, and 10% - 30% chance the surge will exceed 5 feet. In theory, a Category 2 hurricane moving WNW at 5 mph can bring a storm surge of up to 8 - 9 feet to the South Texas and northern Mexican coast.

Other Impacts
Alex is bringing bands of heavy rain to the coasts of Texas and Mexico, as seen on the Brownsville, Texas radar. Hurricane local statements with projections for how Alex will affect the coast are now being issued by the National Weather Service in Brownsville and Corpus Christi. Flooding damage from the expected 6 - 12 inches of rain from Alex will be the main concern. Wind damage is a lesser concern, since the core of Alex is making landfall in a swampy, sparsely populated region of Mexico. The combined wind, surge, and flooding damage from Alex may be similar to 2008's Hurricane Dolly, which hit near Brownsville. Dolly was a Category 2 hurricane offshore that weakened to a Category 1 hurricane with 85 mph winds when it made landfall, and did about $1 billion in damage. Dolly also generated two weak EF-0 tornadoes, and Alex is capable of generating a few tornadoes as well, according to the latest discussion from NOAA's Storm Prediction Center. The atmosphere is moderately unstable, there is plenty of moisture, and wind shear at low levels has been increasing this morning. The greatest threat for tornadoes will occur late this afternoon, on the right side of where the storm makes landfall.

Alex in historical context
Alex is the first June hurricane since Hurricane Allison of 1995. Allison briefly became a minimal 75 mph hurricane before weakening and hitting the Florida Panhandle as a tropical storm. Alex is the strongest June hurricane since Hurricane Bonnie of 1986, which had 85 mph winds. Bonnie was the first hurricane I flew into as a member of the Hurricane Hunters. Bonnie made landfall along the upper Texas coast, and caused less than $20 million in damage. If Alex strengthens to 90 mph winds, it will be the strongest June hurricane since Hurricane Alma of 1966, which had 125 mph winds as it skirted the Florida Keys. There have been only ten hurricanes in May or June since 1945; only four of these were major Category 3 or higher storms.

Track forecast for Alex
All of the models take Alex to the west or west-northwest into northern Mexico by early Thursday morning. However, the steering currents are fairly weak, and Alex could stall and move erratically at times today. I don't anticipate that this weakness in the steering currents will allow Alex to move northward and make landfall in Texas. After landfall, the ridge of high pressure forcing Alex westward should remain in place and strengthen, keeping Alex's remnants over northern Mexico for several days.

Intensity forecast for Alex
Alex is over a region of ocean with moderately high total ocean heat content . Wind shear has fallen to a low 5 knots, and is projected by the SHIPS model to remain in the low range, below 10 knots, through landfall. The combination of low wind shear, moderately high ocean heat content, and plenty of moisture should allow Alex to continue to intensify today. Alex's pressure is already characteristic of a Category 3 hurricane, but the storm is so large that it is taking time for the winds to catch up to the pressure falls. It is unlikely that Alex's winds will be at Category 3 strength at landfall, since the storm is undergoing an eyewall replacement cycle, and does not have time to build a tight inner eyewall with strong winds before landfall. A Category 2 storm at landfall looks more likely.

Elsewhere in the tropics
The latest run of the NOGAPS model predicts the formation of a tropical disturbance in the Western Caribbean on Monday. None of the other models is showing anything brewing over the coming seven days.

Wind and ocean current forecast for the BP oil disaster
Alex is generating very rough conditions over the Deepwater Horizon blowout location, with 6 - 8 foot waves and 3 - 4 foot swells. Strong southeast to south winds of 15 - 25 knots will blow over the oil slick region today through Thursday, according to the latest marine forecast from NOAA. The resulting currents will push oil to many protected bays and estuaries that haven't seen oil yet. In addition, the 1 - 2 foot storm surge Alex is generating along the Louisiana coast will act to push oil deep into some low-lying marshlands. While this oil will be diluted some by the wave action, the impact of the oil and accompanying toxic dispersants on the marshlands is of concern. The latest trajectory forecasts from NOAA and the State of Louisiana show oil will also move westward along the central Louisiana coast towards the Texas border. Winds will decrease to 10 - 15 knots Friday through Monday but remain out of the southeast, keeping the pressure on the regions of coast in Louisiana, Alabama, and Mississippi that are seeing oil hit their shores this week.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Next post
Either Rob Carver or myself will do an update late this afternoon or this evening.

Jeff Masters

Hurricane

Updated: 10:21 PM GMT del 03 Gennaio 2012

Permalink

Alex Becomes a Hurricane

By: JeffMasters, 02:57 AM GMT del 30 Giugno 2010

Hi, Dr. Rob Carver filling in for Jeff on the late shift.

430AM EDT Update
The 400AM EDT advisory package has hit the wires. Alex' center of circulation is located at 23.3N, 95.1W, which is 175 miles east of La Pesca, MX and 235 miles southeast of Brownsville, TX. Alex is responding to a weakness in the ridge to it's north, the storm motion has shifted to WNW at 7 mph. The winds are unchanged from the 100AM advisory, they are still 80 mph. However, Alex continues to deepen it's pressure, the minimum central pressure is 961 mb. Hurricane force winds now extend to 30 miles away from the center, and tropical force winds extend to 200 miles from the center. Alex is currently over warm ocean waters and under weak vertical shear, so the winds are forecast to increase. However, given the strength of Alex's central pressure, there is a small possibility of a rapid intensification of an additional 35 mph.

I haven't changed my risk assessment with this advisory. Flooding from rain still remains the greatest hazard posed by Alex. Tropical storm force winds are expected to reach the coast later this morning. People should plan on finishing their outdoor preparations by this time.

150 AM Update As of the 100AM EDT advisory, Alex is at 23.1N, 94.8W. The minimum central pressure is 972 mb, and the winds have increased to 80 mph. Alex is slowly moving westwards at 5 mph in an "erratic" fashion.

As of the 11PM EDT advisory, NHC has upgraded Alex to a hurricane with maximum winds of 75 mph and a minimum central pressure of 973 mb. Alex's center is at 23.1N, 94.8W, which is 255 miles south of Brownsville, TX and 195 miles east-southeast of La Pesca, MX. Alex is moving westwards at 9 mph. Alex is expected to slightly alter it's course to the WNW before making landfall south of the Rio Grande. The winds are also forecast to pick up to 90 mph before landfall. In any event, mandatory evacuation orders have been issued for recreational vehicles and other high-profile vehicles in county parks on South Padre Island. A voluntary evacuation is in place for residents of South Padre Island and Port Isabel.

Threat from storm surge
NHC is forecasting a 3-5 foot storm surge north of the eye as Alex makes landfall.

Threat from wind
NWS forecasters expect that damage from Alex's winds will be limited to the southern counties of Cameron, Willacy, and Hidalgo. Hurricane force winds extend 15 miles from the storm center, but tropical storm force winds extend 175 miles from the center. This is a rather large circulation. The Storm Prediction Center is monitoring southern Texas for the threat of tornadoes in the outer rainbands as Alex makes landfall. I'd expect a tornado watch to be issued around noon CDT.

Threat from rain
This is the most significant impact from Alex. Rainfall totals of 6 to 12 inches are expected over northern Mexico/southern Texas with 20 inches possible in some locations. There will be flooding from this storm. If more than 5 inches fall in 6 hours, there will likely be flash flooding. The NWS office in Brownsville is advising people who were flooded out by Dolly in 2008 to evacuate to higher ground now.


Satellite-derived rainfall estimates for Alex's passage over the Yucatan peninsula on June 28, 2010. Data provided by the Climate Prediction Center.

Alex is the first Atlantic June hurricane since 1995's Allison. The storm tally for that season was 19 named storms, 11 hurricanes, and 5 major hurricanes. It will be interesting to see how this season compares to 1995.

Next update
I'll have an update Wednesday evening/night. Jeff will have an update sometime tomorrow morning.

Hurricane

Updated: 12:22 PM GMT del 30 Giugno 2010

Permalink

Alex building an eyewall, still not a hurricane

By: JeffMasters, 07:34 PM GMT del 29 Giugno 2010

Tropical Storm Alex is slowly building an eyewall, which is now more than 50% complete, according to recent satellite imagery and microwave images (Figure 1.) Satellite loops show a slot of dry air is spiraling into the center of the storm, and until this dry slot gets closed off, Alex will not be able to intensify significantly. Alex's heavy thunderstorms and low level spiral bands continue to slowly increase, but upper-level outflow is mediocre to the north and east, and absent elsewhere. The Hurricane Hunters are in the storm and have not found any hurricane-force winds at the surface yet.


Figure 1. Microwave "radar in space" image taken at 10:11 am CDT Tuesday June 28, 2010, showing that Alex had built an eyewall a little more than 50% complete. Image credit: Navy Research Lab.

Impacts
Alex is already bringing bands of heavy rain to the coasts of Texas and Mexico, as seen on the Brownsville, Texas radar. Hurricane local statements with projections for how Alex will affect the coast are now being issued by the National Weather Service in Brownsville and Corpus Christi. Since Alex is a large storm, it will have a storm surge that will affect most of the South Texas coast. NHC is giving a 40% - 60% chance of a storm surge of at least 3 feet affecting the Brownsville area, and 10% - 30% chance the surge will exceed 5 feet. In theory, a Category 2 hurricane moving WNW at 5 mph can bring a storm surge of up to 8 - 9 feet to the South Texas coast (Figure 2.) However, Alex is now unlikely to get that strong, and the surge should be less. Flooding damage from the expected 6 - 12 inches of rain from Alex will also be a major concern, as will wind damage. The combined wind, surge, and flooding damage from 2008's Hurricane Dolly, which hit near Brownsville, were about $1.05 billion. Dolly was a Category 2 hurricane offshore that weakened to a Category 1 hurricane with 85 mph winds when it made landfall. I expect Alex will be similar in its impacts to Dolly, though Alex's storm surge damage is likely to be greater. If Alex hits more than 50 miles south of the Texas border, as currently appears likely, the damage will be far less, since this region of the coast is relatively sparsely populated.


Figure 2. Maximum Water Depth (storm tide minus the elevation of the land it is passing over) computed using the primary computer model used by the National Hurricane Center (NHC) to forecast storm surge--the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model. The accuracy of the SLOSH model is advertised as plus or minus 20%. The "Maximum Water Depth" image shows the water depth at each grid cell of the SLOSH domain. Thus, if you are inland at an elevation of five feet above mean sea level, and the combined storm surge and tide (the "storm tide") is ten feet at your location, the water depth image will show five feet of inundation. This Maximum of the "Maximum Envelope of Waters" (MOM) image was generated for high tide, and thus shows the worst-case inundation scenarios for a mid-strength Category 2 hurricane moving WNW at 5 mph. For more information on storm surge, consult our detailed storm surge pages.

Track forecast for Alex
The latest 12 UTC (7am CDT) runs of our most reliable computer models confirm the faster movement of Alex to the coast, and residents in the affected areas now have 12 hours less to prepare for Alex's arrival than it seemed with yesterday's forecasts. Conditions will begin to deteriorate along the coast late tonight, so today is the day to finish preparations if you live near the Texas/Mexico border! The ridge that is steering Alex to the northwest is expected to strengthen today and Wednesday, which should push Alex on a more west-northwest and then westerly track on Wednesday. A few models even have Alex moving west-southwest by the time it makes landfall. The most northerly landfall location, near Brownsville, is predicted by the HWRF model.

To get the probability of receiving tropical storm force winds or hurricane force winds for your location, I recommend the NHC wind probability forecasts. The 4am CDT (9 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 88% chance of tropical storm conditions (winds 39+ mph), 23% chance of hurricane force winds (74+ mph). This is the cumulative probability through Saturday morning. The wind probability forecasts also include separate probabilities for each 12-hour period between now and three days from now, and each 24 hours for the period 4 - 5 days from now.

Corpus Christi, TX: 42% tropical storm, 1% hurricane.

La Pesco, MX: 37% tropical storm, 3% hurricane.

Freeport, TX: 18% tropical storm, 0% hurricane.

Tampico, MX: 14% tropical storm, 0% hurricane.

Galveston, TX: 13% tropical storm, 0% hurricane.

Intensity forecast for Alex
Alex is over a region of ocean with a warm, clockwise rotating Loop Current eddy that broke off from the Loop Current in July 2009 and moved west-southwest over the past 11 months. This eddy has moderately high total ocean heat content . Wind shear has fallen to a low 5 knots, and is projected by the SHIPS model to remain in the low range, below 10 knots, this afternoon and Wednesday. The combination of low wind shear and moderately high ocean heat content should allow Alex to intensify into a Category 1 hurricane, but time is running out for it to be a Category 2 hurricane. NHC is giving Alex a 79% chance of being a hurricane on Wednesday morning, and a 4% chance it will be a major hurricane at that time. Water vapor satellite images show the amount of dry air over the western Gulf of Mexico has decreased over the past day, though as I noted above, the dry slot wrapping into Alex's core is currently keeping the storm from closing off an eyewall. Dry air may turn out to be an increasing detriment to Alex on Wednesday as the storm approaches land. Another factor limiting Alex's intensification may be that the atmosphere is more stable than usual right now--temperatures at 200 mb are a rather warm -50°C, and are expected to warm an additional 1 - 2 degrees by Wednesday. I don't expect Alex to stall out again, so slow motion leading to upwelling of cold water will probably not be a problem for Alex. The main issue limiting intensification will be the fact that Alex is so large, and it takes more time for a large storm to organize. Thus, I think Alex has only a 10% chance of intensifying into a major hurricane before landfall.

Elsewhere in the tropics
The last few runs of the NOGAPS model have been predicting the formation of a tropical disturbance off the coast of Nicaragua on Friday or Saturday that will move northwestward towards western Cuba. The GFS model, and the two models that use it for starting conditions, the GFDL and HWRF, are indicating the possibility that a weak extratropical storm may form along coastal Alabama this weekend. It is unlikely that such a storm would be over water long enough to transition to a tropical storm.

Wind and ocean current forecast for the BP oil disaster
It currently appears that Alex's winds will not directly affect the oil slick location. However, because Alex is such a deep low pressure region, strong southeast to south winds of 10 - 20 knots will blow over the oil slick region today through Thursday, according to the latest marine forecast from NOAA. The resulting currents should act to push oil to the west and northwest onto portions of the Louisiana, Mississippi, and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Oil will also move westward along the central Louisiana coast towards the Texas border. Alex is currently bringing swells of 3 - 4 feet to the coastal regions impacted by the oil slick, and these swells will increase to 6 - 8 feet on Wednesday. Wave heights will increase to 5 - 7 feet on Wednesday. Alex is expected to bring a storm surge of 1 - 2 feet along the coast in the oil spill region. The swells and waves that will accompany these high water levels will act to push oil deep into the marshlands in some locations. The long range forecast for the oil slick region is uncertain, due to the possibility a weak area of low pressure might develop late this week along the remains of a cold front draped across the region.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Alex
2) A look ahead at what may happen the rest of hurricane season

Today's show will be about 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Next post
I'll have an update Wednesday morning by 9:30am CDT. Rob Carver is planning on doing a late-night update tonight.

Jeff Masters

Hurricane

Updated: 10:23 PM GMT del 03 Gennaio 2012

Permalink

Alex still not a hurricane

By: JeffMasters, 02:19 PM GMT del 29 Giugno 2010

Tropical Storm Alex continues to slowly grow more organized as it heads towards the Texas/Mexico border. Satellite loops continue to show a slow increase in Alex's heavy thunderstorms and low level spiral bands. An impressive large thunderstorm with very cold tops has erupted near Alex's center in the past hour, and this may be a "hot tower" that presages the formation of an eye. The latest Hurricane Hunter center fix at 6:29am CDT found a central pressure of 982 mb, which is a typical Category 1 hurricane pressure. However, as of 9am CDT, the Hurricane Hunters has still not found hurricane-force winds at the surface in Alex. The clockwise flow around an upper-level high pressure system a few hundred miles west of Alex is bringing about 10 - 15 knots of wind shear to the storm, which is slowing intensification. Heavy thunderstorm activity is still limited on the storm's northwest side, thanks to the shear and some dry continental air flowing off the coast of North America. Sea Surface Temperatures are very warm, 29°C.

Impacts
Hurricane local statements with projections for how Alex will affect the coast are now being issued by the National Weather Service in Brownsville and Corpus Christi. Since Alex is a large storm, it will have a storm surge that will affect most of the South Texas coast. NHC is giving a 30% - 40% chance of a storm surge of at least 4 feet affecting the Brownsville area, and 10% - 20% chance the surge will exceed 5 feet. In theory, a Category 2 hurricane moving WNW at 5 mph can bring a storm surge of up to 8 - 9 feet to the Southern Texas coast (Figure 1.) Of course, flooding damage from the expected 10 - 20 inches of rain from Alex will also be a major concern, as will wind damage. The combined wind, surge, and flooding damage from 2008's Hurricane Dolly, which hit near Brownsville, were about $1.05 billion. Dolly was a Category 2 hurricane offshore that weakened to a Category 1 hurricane with 85 mph winds when it made landfall. I expect Alex will be similar in its impacts to Dolly, though Alex's storm surge damage is likely to be greater.


Figure 1. Maximum Water Depth (storm tide minus the elevation of the land it is passing over) computed using the primary computer model used by the National Hurricane Center (NHC) to forecast storm surge--the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model. The accuracy of the SLOSH model is advertised as plus or minus 20%. The "Maximum Water Depth" image shows the water depth at each grid cell of the SLOSH domain. Thus, if you are inland at an elevation of five feet above mean sea level, and the combined storm surge and tide (the "storm tide") is ten feet at your location, the water depth image will show five feet of inundation. This Maximum of the "Maximum Envelope of Waters" (MOM) image was generated for high tide, and thus shows the worst-case inundation scenarios for a mid-strength Category 2 hurricane moving WNW at 5 mph. For more information on storm surge, consult our detailed storm surge pages.

Track forecast for Alex
The latest 0 UTC and 6 UTC (1am CDT) runs of our most reliable computer models did a pretty poor job, in general, of capturing the north-northwest motion of Alex early this morning, and are thus probably too far south in their landfall predictions. The official NHC forecast is thus taking Alex farther north than the models are. The most northerly landfall location, near Port Mansfield, is now being predicted by the HWRF model. The most southerly landfall prediction comes from the ECMWF model, which predicts landfall more than 100 miles south of Brownsville.

To get the probability of receiving tropical storm force winds or hurricane force winds for your location, I recommend the NHC wind probability forecasts. The 4am CDT (9 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 84% chance of tropical storm conditions (winds 39+ mph), 23% chance of hurricane force winds (74+ mph). This is the cumulative probability through Saturday morning. The wind probability forecasts also include separate probabilities for each 12-hour period between now and three days from now, and each 24 hours for the period 4 - 5 days from now.

Corpus Christi, TX: 44% tropical storm, 4% hurricane.

La Pesco, MX: 42% tropical storm, 3% hurricane.

Freeport, TX: 22% tropical storm, 0% hurricane.

Tampico, MX: 20% tropical storm, 0% hurricane.

Galveston, TX: 16% tropical storm, 0% hurricane.

Uncertainty in the NHC Cone of Uncertainty
A research project funded by NOAA known as the Joint Hurricane Testbed has produced a remarkable number of tools now in operational use at the National Hurricane Center to improve hurricane forecasts and warnings. One of these projects, called "Prediction of Consensus TC Track Forecast Error and Correctors to Improve Consensus TC Track Forecasts", was an effort by Dr. Jim Goerss at the Navy Research Lab to improve the accuracy of the NHC "cone of uncertainty" (AKA the "Cone of Death") showing where a storm is expected to track 2/3 of the time. The radius of the circles that make up the cone are based on error statistics of the official NHC forecast over the past five years. We can expect in certain situations, such as when the models are in substantial disagreement, a consensus forecast made using these models will have much greater than average errors. Since the NHC typically bases their forecast on a consensus forecast made using a combination of reliable hurricane forecasting models, it is instructive to view the "GPCE" (Goerss Prediction Consensus Error) circles to see if the uncertainty cone should be smaller or larger than usual. The consensus forecast I'll look at is called "TVCN", and is constructed by averaging the track forecasts made by most of (or all) of these models: GFS, ECMWF, NOGAPS, GFDL, HWRF, GFDN, and UKMET. In the case of this morning's 12 UTC (7am CDT) June 28 run of these models, here is what the radius of the "cone of uncertainty" should be, in nautical miles:

12 hours: 36 nm
24 hours: 59 nm
36 hours: 82 nm
48 hours: 119 nm

And here is the radius of NHC's "cone of uncertainty" for their official forecast, based on the average errors for the past five years:

12 hours: 36 nm
24 hours: 62 nm
36 hours: 85 nm
48 hours: 108 nm

So, the GPCE error estimates are showing that the latest forecasts for Alex out to 48 hours are are pretty close to average.


Figure 2. Tropical Cyclone Heat Potential (TCHP) for Monday, June 28, 2010 at 7pm CDT, with the official NHC forecast track for Alex overlaid. Alex will be passing directly over the core of a warm Loop Current eddy that broke off from the Loop Current back in July 2009. Values of TCHP in excess of 90 kJ/cm^2 commonly cause rapid intensification of hurricanes. Alex will be passing over waters with less TCHP than that. Image credit: NOAA RAMMB/Colorado State University.

Intensity forecast for Alex
Alex is approaching a region of ocean with with a warm, clockwise rotating Loop Current eddy that broke off from the Loop Current in July 2009 and moved west-southwest over the past 11 months. This eddy has moderately high total ocean heat content (Figure 2.) Wind shear is currently a moderate 10 - 15 knots, and is projected by the SHIPS model to decrease to the low range, below 10 knots, this afternoon and Wednesday. The combination of low wind shear and moderately high ocean heat content should allow Alex to intensify into a Category 2 hurricane. NHC is giving Alex a 79% chance of being a hurricane on Wednesday afternoon, and a 9% chance it will be a major hurricane at that time. Water vapor satellite images show the amount of dry air over the western Gulf of Mexico has decreased over the past day, though dry air may turn out to be a detriment to Alex on Wednesday as the storm approaches land. Another factor limiting Alex's intensification may be that the atmosphere is more stable than usual right now--temperatures at 200 mb are a rather warm -50°C, and are expected to warm an additional 1 - 2 degrees by Wednesday. I don't expect Alex to stall out again, so slow motion leading to upwelling of cold water will probably not be a problem for Alex. The main issue limiting intensification will be the fact that Alex is so large, and it takes more time for a large storm to organize. Thus, I think Alex has only a 20% chance of intensifying into a major hurricane before landfall.

Elsewhere in the tropics
The last two runs of the NOGAPS model has been predicting the formation of a tropical disturbance off the coast of Nicaragua on Friday or Saturday that will move northward towards Jamaica and Cuba. The GFS model, and the two models that use it for starting conditions, the GFDL and HWRF, are indicating the possibility that a weak extratropical storm may form along coastal Alabama late this week. It is unlikely that such a storm would be over water long enough to transition to a tropical storm.

Wind and ocean current forecast for the BP oil disaster
It currently appears that Alex's winds will not directly affect the oil slick location. However, because Alex is such a deep low pressure region, strong southeast to south winds of 10 - 20 knots will blow over the oil slick region today through Thursday, according to the latest marine forecast from NOAA. The resulting currents should act to push oil to the west and northwest onto portions of the Louisiana, Mississippi, and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Oil will also move westward along the central Louisiana coast towards the Texas border. Alex is expected to bring a storm surge of 2 - 3 feet along the coast in the oil spill region, which will push oil deep into the marshlands in some locations. The long range forecast for the oil slick region is uncertain, due to the possibility a weak area of low pressure might develop late this week along the remains of a cold front draped across the region.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Alex
2) A look ahead at what may happen the rest of hurricane season

Today's show will be about 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Next post
I'll have an update between 2 - 3 pm CDT today, when the latest set of models runs will be available.

Jeff Masters

Hurricane

Updated: 10:23 PM GMT del 03 Gennaio 2012

Permalink

Alex Slowly Gains Strength

By: JeffMasters, 06:35 AM GMT del 29 Giugno 2010

Hello, it's Dr. Rob Carver substituting for Jeff on the late shift.

As of the 0100 EDT advisory, Alex is 475 miles SE of Brownsville TX moving NNW at 8 mph. The advisory wind speed is 65 mph with a minimum central pressure of 985 mb. The most recent vortex fix was at 1225EDT with an unchanged pressure reading. Alex is expected to take a turn to the NW and make landfall just south of Brownsville late Wednesday night/early Thursday morning. The government of Mexico has issued a hurricane warning from the mouth of the Rio Grande south to La Cruz. NHC has hoisted the hurricane warning flag from the Rio Grande north to Baffin Bay. A tropical storm warning extends from Baffin Bay to Port O'Connor. Alex is expected to expand in size so it will be much larger than Hurricane Dolly, which was the last storm to affect the region in 2008.

Hurricane Local Statements are now being issued by the Brownsville and Corpus Christi NWS offices. These statements provide a detailed look at how Alex will affect the region and summarize how local emergency management is responding to the situation.

Alex has three different ways to negatively impact the Rio Grande Valley: storm surge, heavy rains, and strong winds.

Risk of Storm Surge
NHC is forecasting a storm surge of 3-5 feet along the coast north of where Alex makes landfall. The exact details of the surge's extent depend on where Alex makes landfall and how big it gets while it is over the open water. I've include a plot of the statistical storm surge forecast product. Unless Alex refuses to make it's left turn, I don't think there's a chance of storm surge north of Port O'Connor.

Plot of experimental storm surge forecast.

Threat from Rain
NHC thinks 5 to 10 inches of rain over southern Texas/northern Mexico is possible when Alex makes landfall. This is why the Brownsville office thinks the primary threat from Alex will be inland flooding in areas with poor drainage.

Alex has a history of producing torrential amounts of rain as shown by this estimate of rainfall during Alex's passage over the Yucatan Peninsula.

Satellite-derived rainfall estimates for June 27, 2010 using data from the Climate Prediction Center.

Threat from Wind
Alex is currently forecast to reach hurricane status. There will likely be hurricane force winds along the coast where Alex makes landfall. The current hurricane wind probabilities show that Brownsville has a 77% chance of experiencing tropical storm force winds and a 18% chance of experiencing hurricane force winds. Corpus Christi has a 44 % chance of tropical storm winds and a 4% chance of hurricane force winds. There is also the possibility of tornadoes forming in outer rainbands as Alex makes landfall.

The Curious Incident of the Hurricane Dynamical Models
One thing that strikes me as odd about Alex is that neither the GFDL nor the HWRF have been intensifying the storm into a hurricane in the past few model runs. This is intriguing because Alex is already a strong tropical storm. It will bear watching to see if GFDL/HWRF continue this pattern for future storms.

Next Update
Jeff will post an entry sometime this morning, and I'll have another entry late Tuesday night.

Hurricane

Updated: 06:43 AM GMT del 29 Giugno 2010

Permalink

Alex continues to slowly organize

By: JeffMasters, 07:17 PM GMT del 28 Giugno 2010

Tropical Storm Alex continues to slowly grow more organized as it steams away from Mexico's Yucatan Peninsula. Satellite loops show that Alex's heavy thunderstorms continue to increase in areal extent, and low level spirals bands are slowly building to the south and north. The clockwise flow around an upper-level high pressure system a few hundred miles west of Alex is bringing about 15 knots of wind shear to the storm, which is slowing intensification. Heavy thunderstorm activity is limited on the storm's northwest side, thanks to the shear and some dry continental air flowing off the coast of North America. Sea Surface Temperatures are very warm, 29°C. The latest Hurricane Hunter center fix, at 12:07 pm CDT, showed a central pressures of 990 mb, a 1 mb rise in six hours. Top winds were holding steady near 60 mph. Alex has stalled out the last few hours, as it began to "feel" the trough of low pressure to its north breaking down the high pressure ridge that has been pushing the storm to the west-northwest. This stall has allowed the storm to churn up cold water from the depths, which is probably interfering with development. Satellite loops show that Alex has a very large circulation covering about 2/3 of the Gulf of Mexico. We can expect that should Alex become a Category 2 or stronger hurricane, its storm surge will affect a much wider stretch of coast than Hurricane Dolly of 2008 did.


Figure 1. Afternoon satellite image of Alex.

Track forecast for Alex
The latest 12 UTC (7am CDT) runs of our most reliable computer models have come into much better agreement. A consensus forecast arrived at by averaging together most or all of the tracks of our top models--the GFS, ECMWF, GFDL, NOGAPS, HWRF, UKMET, and GFDN--is pretty much what NHC always uses as the basis of their forecast. This consensus forecast has narrowed in on the region just south of the Texas/Mexico border as being the most likely landfall location, with the usual cone of uncertainty surrounding it. The computer model that had been making the northernmost landfall predictions, the Canadian model, is now projecting a landfall 100 miles south of the Texas/Mexico border. There has been a general southward shift of the models in their latest runs, and the most northerly landfall location, near Port Mansfield, is now being predicted by the HWRF model. The earliest landfall time is Wednesday morning, and the latest is Thursday morning. Which model should you trust? Last year, the best performing models at the 3 day forecast period were the GFS, Canadian, ECMWF, and GFDL.

With steering currents relatively weak, the uncertainty in landfall location is high. The average error in an NHC 72-hour track forecast last year was 230 miles, which is about the distance from Brownsville to Port O'Connor. Consider also that the NHC cone of uncertainty is the region where 2/3 of the time (using the last 5 years of statistics) the center of a storm will go. Forecast errors tend to be equally large along track (speed errors) and cross-track (deviations from side-to-side), so that means that about 20% of the time a storm will not be in the cone of uncertainty. Given the slow motion of Alex and the recent uncertainty of the computer models, people living just beyond the edge of the cone of uncertainty should not be confident yet that Alex will miss them.

To get the probability of receiving tropical storm force winds or hurricane force winds for your location, I recommend the NHC wind probability forecasts. The 10am CDT (15 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 67% chance of tropical storm conditions (winds 39+ mph), 16% chance of hurricane force winds (74+ mph). This is the cumulative probability through Saturday morning. The wind probability forecasts also include separate probabilities for each 12-hour period between now and three days from now, and each 24 hours for the period 4 - 5 days from now.

La Pesco, MX: 49% tropical storm, 6% hurricane.

Tampico, MX: 31% tropical storm, 4% hurricane.

Corpus Christi, TX: 45% tropical storm, 6% hurricane.

Freeport, TX: 23% tropical storm, 2% hurricane.

Galveston, TX: 21% tropical storm, 1% hurricane.


Figure 2. Skill of computer model forecasts of Atlantic named storms during 2009. OFCL=Official NHC forecast; GFS=Global Forecast System model; GFDL=Geophysical Fluid Dynamic Laboratory model; HWRF=Hurricane Weather Research Forecasting model; NOGAPS=Navy Operational Global Prediction System model; UKMET+United Kingdom Met Office model; ECMWF=European Center for Medium Range Weather Forecasting model; CMC=Canadian GEM model; TVCN=one of the consensus models that lends together all (or most) of the above models; BAMM=Beta and Advection Model (Medium Layer.) Image credit: National Hurricane Center 2009 verification report.

Uncertainty in the NHC Cone of Uncertainty
A research project funded by NOAA known as the Joint Hurricane Testbed has produced a remarkable number of tools now in operational use at the National Hurricane Center to improve hurricane forecasts and warnings. One of these projects, called "Prediction of Consensus TC Track Forecast Error and Correctors to Improve Consensus TC Track Forecasts", was an effort by Dr. Jim Goerss at the Navy Research Lab to improve the accuracy of the NHC "cone of uncertainty" (AKA the "Cone of Death") showing where a storm is expected to track 2/3 of the time. The radius of the circles that make up the cone are based on error statistics of the official NHC forecast over the past five years. We can expect in certain situations, such as when the models are in substantial disagreement, a consensus forecast made using these models will have much greater than average errors. Since the NHC typically bases their forecast on a consensus forecast made using a combination of reliable hurricane forecasting models, it is instructive to view the "GPCE" (Goerss Prediction Consensus Error) circles to see if the uncertainty cone should be smaller or larger than usual. The consensus forecast I'll look at is called "TVCN", and is constructed by averaging the track forecasts made by most of (or all) of these models: GFS, ECMWF, NOGAPS, GFDL, HWRF, GFDN, and UKMET. In the case of this morning's 12 UTC (7am CDT) June 28 run of these models, here is what the radius of the "cone of uncertainty" should be, in nautical miles:

12 hours: 42 nm
24 hours: 73 nm
36 hours: 96 nm
48 hours: 112 nm
72 hours: 173 nm
96 hours: 327 nm
120 hours: 376 nm

And here is the radius of NHC's "cone of uncertainty" for their official forecast, based on the average errors for the past five years:

12 hours: 36 nm
24 hours: 62 nm
36 hours: 85 nm
48 hours: 108 nm
72 hours: 161 nm
96 hours: 220 nm
120 hours: 285 nm

So, the GPCE error estimates are showing that the latest forecasts for Alex out to 72 hours are 4% - 17% higher in uncertainty than average. The 4 - 5 day forecasts are 32% - 49% more uncertain than average--but of course, we expect Alex to be inland at those times.

Intensity forecast for Alex
Alex is currently over a region of ocean with relatively low total ocean heat content (about 10 - 30 kJ/cm^2). By Tuesday and Wednesday, the heat content will increase to 40 - 70 kJ/cm^2, which is high enough to allow Alex to rapidly intensify. Wind shear is currently a moderate 15 knots, and is projected by the SHIPS model to decrease to the low range, below 10 knots, on Tuesday and Wednesday. The combination of low wind shear and high ocean heat content should allow Alex to intensify into a hurricane. NHC is giving Alex a 78% chance of being a hurricane on Wednesday morning, and a 16% chance it will be a major hurricane at that time. Water vapor satellite images, though, show plenty of dry air over Texas and the adjoining waters, and this dry air may turn out to be a significant detriment to Alex. Another factor limiting Alex's intensification may be that the atmosphere is more stable than usual right now--temperatures at 200 mb are a rather warm -50°C, and are expected to warm an additional 1 - 2 degrees by Wednesday. Another factor limiting Alex's intensification may be its slow forward speed. Alex has already stalled out once, and may stall out later in its path, as well. A stalled-out storm tends to pull up cold water from the depths, limiting intensification. In short, Alex has the potential to intensify into a major hurricane, but there are enough roadblocks that I give a 20% chance of this happening.

Elsewhere in the tropics
None of the reliable computers models is calling for tropical storm formation over the the next seven days in the Atlantic.

Wind and ocean current forecast for the BP oil disaster
It currently appears that Alex will not directly affect the oil slick location, other than to bring 2 - 4 foot swells to the region on Wednesday. However, because Alex is such a deep low pressure region, strong southeast winds of 15 - 25 knots will blow over the oil slick region today through Wednesday, according to the latest marine forecast from NOAA. The resulting currents should act to push oil to the west and northwest onto portions of the Louisiana, Mississippi, and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Oil will also move westward along the central Louisiana coast towards the Texas border.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Portlight continues its Haiti response
Hurricane season is here, and Haiti is not ready. Over 1.5 million Haitians are living outside in tents or under tarps, and are highly vulnerable to a hurricane. Portlight is working on constructing steel shelters out of shipping containers for homeless Haitians, as detailed in the Haitian Relief Recap blog post. Please visit the Portlight.org web site or the Portlight blog to learn more and to donate to Portlight's efforts in Haiti.


Figure 3. Still frame from the remarkable video taken inside the Haitian Presidential Palace during the 2010 earthquake.

To remind people of just how devastating the earthquake was, the Haitian government released a video earlier this month showing the inside of the Haitian Presidential Palace during the mighty Haitian earthquake.

Next post
Dr. Rob Carver is planning on making a post late tonight, and I'll have an update by 9:30am CDT on Tuesday.

Jeff Masters

Hurricane

Updated: 12:03 AM GMT del 29 Giugno 2010

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Alex slowly organizing; a Texas or Mexico landfall most likely

By: JeffMasters, 02:13 PM GMT del 28 Giugno 2010

Tropical Storm Alex is slowly growing more organized as it steams away from Mexico's Yucatan Peninsula. Satellite loops show that Alex's heavy thunderstorms have increased in areal extent over the past few hours, and low level spirals bands are beginning to form to the south and north. The clockwise flow around an upper-level high pressure system a few hundred miles west of Alex is bringing about 15 knots of wind shear to the storm, which is slowing intensification, and limiting heavy thunderstorm activity on the storm's northwest side. Sea Surface Temperatures are very warm, 29°C, and there is some dry air to the northwest of Alex that may be inhibiting development. The latest Hurricane Hunter center fixes, at 6:32 am CDT and 7:16 am CDT, both had central pressures of 989 mb, with top surface winds in the 50 - 55 mph range.


Figure 1. Alex over the Yucatan Peninsula on Sunday, June 27, as seen by NASA's Aqua satellite. Image credit: NASA.

Track forecast for Alex: which model should you trust?
Our most reliable computer models have come into much better agreement this morning. A consensus forecast arrived at by averaging together most or all of the tracks of our top models--the GFS, ECMWF, GFDL, NOGAPS, HWRF, UKMET, and Canadian--is pretty much what NHC always uses as the basis of their forecast. This consensus forecast has narrowed in on the region near the Texas/Mexico border as being the most likely landfall location, with the usual cone of uncertainty surrounding it. The northernmost landfall location is Port O'Connor, as predicted by the Canadian model. The southernmost landfall location is near Tampico, Mexico, as predicted by the ECMWF model. Alex's landfall time varies from Wednesday evening to Thursday morning. Which model should you trust? Last year, the best performing models at the 3 day forecast period were the GFS, Canadian, ECMWF, and GFDL. Three out of four of those models are predicting a landfall between Brownsville and Corpus Christi, with only the ECMWF model predicting a landfall well south of the Texas border. With steering currents relatively weak, the uncertainty in landfall location is high. The average error in an NHC 72-hour track forecast last year was 230 miles, which is about the distance from Brownsville to Port O'Connor. Consider also that the NHC cone of uncertainty is the region where 2/3 of the time (using the last 5 years of statistics) the center of a storm will go. That means that 1/3 of the time a storm will not be in the cone of uncertainty. Given the slow motion of Alex and the recent uncertainty of the computer models, people living just beyond the edge of the cone of uncertainty should not be confident yet that Alex will miss them.

To get the probability of receiving tropical storm force winds or hurricane force winds for your location, I recommend the NHC wind probability forecasts. The 5am EDT (09 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 64% chance of tropical storm conditions (winds 39+ mph), 14% chance of hurricane force winds (74+ mph). This is the cumulative probability through Saturday morning. The wind probability forecasts also include separate probabilities for each 12-hour period between now and three days from now, and each 24 hours for the period 4 - 5 days from now.

La Pesco, MX: 59% tropical storm, 9% hurricane.

Tampico, MX: 42% tropical storm, 6% hurricane.

Corpus Christi, TX: 38% tropical storm, 5% hurricane.

Freeport, TX: 23% tropical storm, 2% hurricane.

Galveston, TX: 18% tropical storm, 1% hurricane.


Figure 2. Skill of computer model forecasts of Atlantic named storms during 2009. OFCL=Official NHC forecast; GFS=Global Forecast System model; GFDL=Geophysical Fluid Dynamic Laboratory model; HWRF=Hurricane Weather Research Forecasting model; NOGAPS=Navy Operational Global Prediction System model; UKMET=United Kingdom Met Office model; ECMWF=European Center for Medium Range Weather Forecasting model; CMC=Canadian GEM model; TVCN=one of the consensus models that lends together all (or most) of the above models; BAMM=Beta and Advection Model (Medium Layer.) Image credit: National Hurricane Center 2009 verification report.

Intensity forecast for Alex
Alex is currently over a region of ocean with relatively low total ocean heat content (about 10 - 30 kJ/cm^2). By Tuesday and Wednesday, the heat content will increase to 40 - 70 kJ/cm^2, which is high enough to allow Alex to rapidly intensify. Wind shear is currently a moderate 15 knots, and is projected by the SHIPS model to decrease to the low range, below 10 knots, on Tuesday and Wednesday. The combination of low wind shear and high ocean heat content should allow Alex to intensify into a hurricane. NHC is giving Alex an 81% chance of being a hurricane on Wednesday morning, and a 17% chance it will be a major hurricane at that time. Water vapor satellite images, though, show plenty of dry air over Texas and the adjoining waters, and this dry air may turn out to be a significant detriment to Alex. Another factor limiting Alex's intensification may be that the atmosphere is more stable than usual right now--temperatures at 200 mb are a rather warm -50°C, and are expected to warm an additional 1 - 2 degrees by Wednesday. Another factor limiting Alex's intensification may be its slow forward speed. Alex is moving at just 6 mph, and it would not take much of a slackening of the steering currents to stall out the storm. A slow-moving storm tends to pull up cold water from the depths, limiting intensification. In fact, the ECMWF model predicts that Alex could stall out right at landfall on Thursday. In short, Alex has the potential to intensify into a major hurricane, but there are plenty of roadblocks that make this only a 20% probability in my estimation.

Elsewhere in the tropics
None of the reliable computers models is calling for tropical storm formation over the the next seven days in the Atlantic.

Wind and ocean current forecast for the BP oil disaster
It currently appears that Alex will not directly affect the oil slick location, other than to bring 2 - 4 foot swells to the region on Wednesday. However, because Alex is such a deep low pressure region, strong east to southeast winds of 20 - 25 knots will develop over the oil slick region today through Thursday, according to the latest marine forecast from NOAA. The resulting currents should act to push oil to the west and northwest onto portions of the Louisiana, Mississippi, and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Oil will also move westward along the central Louisiana coast towards the Texas border.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Portlight continues its Haiti response
Hurricane season is here, and Haiti is not ready. Over 1.5 million Haitians are living outside in tents or under tarps, and are highly vulnerable to a hurricane. Portlight is working on constructing steel shelters out of shipping containers for homeless Haitians, as detailed in the Haitian Relief Recap blog post. Please visit the Portlight.org web site or the Portlight blog to learn more and to donate to Portlight's efforts in Haiti.


Figure 3. Still frame from the remarkable video taken inside the Haitian Presidential Palace during the 2010 earthquake.

To remind people of just how devastating the earthquake was, the Haitian government released a a href= video earlier this month showing the inside of the Haitian Presidential Palace during the mighty Haitian earthquake.

Next post
I'll have an update between 2 - 3pm CDT today, when the next set of model runs will be available.

Jeff Masters

Hurricane

Updated: 06:06 PM GMT del 28 Giugno 2010

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Late-night Alex Update

By: JeffMasters, 08:02 AM GMT del 28 Giugno 2010

Hi, Dr. Rob Carver filling in for Jeff on the late shift again.
As of the 11PM EDT advisory, Alex is once more a tropical storm moving to the W-NW at 6 knots. According to the CIMMS wind shear estimates Alex is experiencing less than 20 knots of shear, so it's in a favorable location for intensification. The NHC forecast track has Alex moving to the W-NW and making landfall in northern Mexico.

Disagreement between the forecast models
As of 300EDT, there are roughly three different sets of forecast solutions for the forecast models. CMC/GFS have Alex making landfall along the Texas coast north of Corpus Christi, but south of Houston. GFDL/HWRF have Alex coming ashore near Brownsville. UKMET/ECMWF/NOGAPS/NGFDL show Alex coming ashore well south of the Rio Grande. As was the case yesterday, the difference between the CMC/GFS and UKMET/ECMWF forecast lies in the interaction of the trough with the area of high pressure in the Gulf that's currently steering Alex. Upper-air data from the Gulfstream IV should help refine model forecasts.

What does it mean?
The CMC/GFS/UKMET/ECMWF are all very good global models so it's hard to discount one model in favor for another. If you live along the Gulf coast from Tampico, MX to the Texas/Louisiana border, it would be very prudent to review your hurricane planning and preparations. I still think the chances of Alex directly interfering with oil spill recovery efforts are low.

Rain from Alex
The first satellite-derived rainfall estimates are available for June 26. They show that as Alex was making landfall, it was producing 3-7 inches of rain over the Caribbean Sea.


Satellite-derived rainfall estimates for June 26, 2010 from the Climate Prediction Center

Invest 94L
Invest 94L is no more.

East Asian heat wave continues
The heat wave continues in the Amur river valley between Russia and China. Analysis of gridded data shows that the daily high temperature in that region is 10-14 degrees Celsius above normal.

Plot of daily maximum temperature anomaly in degrees C for June 27, 2010.


Next blog update
Jeff plans on having an entry up by 10AM EDT. I should have another entry up late Monday night.

Hurricane

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Alex may head north to Texas or Louisiana

By: JeffMasters, 06:36 PM GMT del 27 Giugno 2010

Tropical Depression Alex has held together fairly well during its passage over Mexico's Yucatan Peninsula, and stands poised to re-intensify back into a tropical storm once it emerges from the coast tonight. Alex brought heavy rains to northern Honduras, Mexico's Yucatan Peninsula, and Belize over the weekend. It was not a good beach day in Cozumel yesterday, as 9.25" of rain fell. Cancun received 2.05" over the weekend, and Belize City received 4.57". Satellite loops show that Alex's heavy thunderstorms are mostly gone near the center, though there are some impressive bands of precipitation well away from the center. There is an upper-level high pressure system a few hundred miles west of Alex, and the clockwise flow air around this high is bringing upper-level winds out of the northwest of about 5 knots over the storm, contributing to the 5 knots of wind shear observed in this afternoon's wind shear analysis from the University of Wisconsin's CIMSS group. Sea Surface Temperatures are very warm, 29 - 30°C, and dry air is currently not a problem for Alex.


Figure 1. Afternoon satellite image of Alex.

Forecast for Alex: which model should you trust?
While the track forecast for Alex today through Monday is fairly well-assured, the longer range forecast has become highly uncertain. An increasing number of our reliable models are now indicating Alex may take a more northerly track beginning on Tuesday, with possible landfall on the Texas coast near Galveston on Friday (according to the 8am run of the GFS model) or into western Louisiana on Wednesday (the 8am run of the Canadian model.) The key question remains how Alex will react to the trough of low pressure expected to swing down over the Eastern U.S. on Monday and Tuesday. Most of the models were predicting that the trough would not be strong enough to swing Alex to the north, and several of them continue to predict this. The 8am runs of the NOGAPS and ECMWF models, for example, take Alex into the Gulf coast of Mexico 150 miles south of Texas, on Wednesday. The GFDL and HWRF models split the difference, with the GFDL predicting a Thursday landfall in southern Texas near Brownsville, and the HWRF predicting a Thursday landfall near Corpus Christi. Morris Bender of the GFDL group has just provided me the track forecast from an improved experimental version of the GFDL that shows landfall between Corpus Christi and Galveston. So which model should you trust? Last year, the best performing models at the 3 - 4 day forecast range were the GFS and the Canadian, and these are the models that are currently calling for the more northerly track towards the upper Texas coast and Louisiana. Residents of those areas should review their hurricane preparedness plans and anticipate that Alex could make landfall as early as Wednesday in their vicinity. Residents of the Mexican coast south of Brownsville should make similar plans, as Alex could just as easily hit there.

Re-intensification of Alex is likely once the center of Alex moves offshore, though this will initially be slow due to the current disorganized state of the storm and the relatively low total ocean heat content in the 100-mile-wide stretch of water on the west side of the Yucatan Peninsula. Once Alex moves more than 100 miles from the Yucatan, total heat content of the ocean increases substantially, and Alex will have the opportunity to intensify significantly. A longer time spent over water will give Alex more of a chance to strengthen, and it is possible Alex could intensify into a major hurricane if landfall is delayed until Thursday or Friday. However, Alex's intensification may be limited the farther north it gets, as water vapor satellite images show plenty of dry air over Texas that might interfere with development. Wind shear might also be an issue for Alex if it pushes far enough north, and a slow-moving storm tends to pull up cold water from the depths, limiting intensification. In short, Alex has the potential to intensify into a major hurricane, but there are plenty of roadblocks that make this only a 10% probability in my estimation.


Figure 2. Skill of computer model forecasts for Atlantic named storms during 2009. OFCL=Official NHC forecast; GFS=Global Forecast System model; GFDL=Geophysical Fluid Dynamic Laboratory model; HWRF=Hurricane Weather Research Forecasting model; NOGAPS=Navy Operational Global Prediction System model; UKMET+United Kingdom Met Office model; ECMWF=European Center for Medium Range Weather Forecasting model; CMC=Canadian GEM model; TVCN=one of the consensus models that lends together all (or most) of the above models; BAMM=Beta and Advection Model (Medium Layer.) Image credit: National Hurricane Center 2009 verification report.

Elsewhere in the tropics
A tropical wave (Invest 94L) a few hundred miles north of the northernmost Lesser Antilles Islands has been pretty much torn apart, and is no longer a threat to develop.

Next post
Wunderground's severe weather expert Dr. Rob Carver will likely be posting an update on Alex late tonight. My next update will be Monday by 10am EDT.

Jeff Masters

Hurricane

Updated: 08:31 PM GMT del 27 Giugno 2010

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Tropical Storm Alex's Yucatan Landfall

By: JeffMasters, 08:52 AM GMT del 27 Giugno 2010

Update: Here's the 500AM EDT radar image from Belize. Alex's eye is roughly 150 km NW of the radar.


This Animated loop shows the development of Alex's eye. The page for Belize's radar is here.

The 500AM EDT forecast is a bit different than the previous forecast. Essentially, it looks like the area of high pressure in the northern Gulf of Mexico will weaken due to a trough over the eastern US. This will weaken the steering currents and slow's Alex's motion over the Gulf of Mexico. The reduced storm motion will give Alex more time to intensify in a a warm SST/weak shear environment. The current forecast calls for Alex to become a category 2 storm before making landfall north of Tampico, MX late Wed. night/early Thursday morning.

The $64,000 question is "Will the ridge continue to weaken, allowing Alex to move north and continue intensification?" The 12Z global model runs will have more accurate forecasts than the the 6Z runs thanks to the presence of radiosonde data, so hopefully they'll provide an answer. It's still my opinion that Alex will not directly impact the oil spill recovery efforts, but I can't say that the chances of it doing so are getting smaller now.

This is Dr. Rob Carver, filling in for Jeff during the late shift. Tropical Storm Alex is currently moving over the Yucatan peninsula. Alex's intensity has dropped to 50 knots in the latest advisory with further weakening expected as the storm moves over land. After Alex moves into the Gulf of Mexico, intensification is expected because of warm sea-surface temperatures and weak vertical wind shear. An area of high pressure in the northern Gulf of Mexico will guide Alex into a WNW-NW track. The 200AM EDT forecast calls for Alex to intensify into a category 1 hurricane before making landfall just north of Tampico, MX.

In my judgement, the chances of Alex moving northwards and directly interfering with the Deepwater Horizon oil spill recovery efforts are small and getting smaller with time. I agree with Jeff's assessment that Alex will generate 2+ foot swells that would interfere with skimming operations

Currently, the main threat from Alex is flooding due to heavy rains. NHC is forecasting rainfall amounts from 4 to 8 inches with higher amounts over mountainous terrain, causing flooding and possibly mudslides.


Fig. 1Forecast of 24-hour accumulated precipitation from TS Alex.

Alex's Belizean Landfall
Jeff saved this radar image of Alex making landfall.

Fig. 2Base reflectivity at 2315Z 26 June 2010 at Philip Goldson Airport

There isn't much storm structure apparent in the reflectivity data, just widespread areas of showers. Data from a nearby PWS shows that the peak windspeed was 43 mph. You can clearly see the circulation move past the station with changes in the wind direction and speed. You can also see when the rainbands passed over the station.

Invest 94L
Invest 94L is still out there, but it's not looking healthy. It's currently in an area unfavorable for tropical cyclogenesis and NHC thinks it has a 0% chance of becoming a tropical storm in the next two days. Current forecast models have 94L moving northwards and making a pass by Bermuda.

If things don't change significantly, Jeff is thinking about taking Sunday off. However, rest assured that if Alex starts charging towards the US, Jeff or I will put up a new entry. In any event, I'm planning on posting an update sometime late Sunday evening.

Hurricane

Updated: 09:44 AM GMT del 27 Giugno 2010

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Tropical Storm Alex bears down on the Yucatan; extreme heat for Africa and Russia

By: JeffMasters, 02:12 PM GMT del 26 Giugno 2010

The first named storm of the Atlantic hurricane season of 2010 is here. Tropical Storm Alex formed last might from an African tropical wave that plowed through the Caribbean this week. Alex's formation location is a typical one for June tropical storms, and the formation date of June 25 is also a fairly typical date for the first storm of the season to form (we average about one June named storm every two years in the Atlantic.) Heavy rainfall will ramp up through the day in Honduras, Belize, and Mexico's Yucatan Peninsula, as Alex continues to intensify, and flooding from these heavy rains will be the main concern from Alex today and Sunday. Satellite loops show that Alex's heavy thunderstorm are growing in intensity and areal coverage at a respectable pace. There is an upper-level high pressure system a few hundred miles west of Alex, and the clockwise flow air around this high is bringing upper-level winds out of the northwest of about 10 knots over the storm, contributing to the 10 knots of wind shear observed in this morning's wind shear analysis from the University of Wisconsin's CIMSS group. Sea Surface Temperatures are very warm, 29 - 30°C, and dry air is not a problem for Alex. We currently don't have a Hurricane Hunter aircraft in the storm, so we will have to wait until 2pm this afternoon to get an updated estimate of Alex's surface winds. The latest satellite estimates of Alex's winds at 8am EDT put the storm's strongest winds at 40 mph.


Figure 1. Satellite image of the tropics at 9am EDT Saturday 6/26/10. Image credit: GOES Science Project.

Forecast for Alex
As I discussed in last night's post, an examination of the nineteen tropical cyclones that have formed in the Western Caribbean and hit the Yucatan Peninsula over the past twenty years reveals that 8 went on to make a second Gulf Coast landfall in Mexico, 5 hit the U.S. Gulf Coast, and 6 died after hitting the Yucatan. The ones that died all took a more southerly path across the Yucatan, spending more time over land than Alex will. Alex is large enough and moving far enough north across the Yucatan that passage over the peninsula will not kill it. So, will Alex follow the path climatology says is more likely, and make a second landfall along the Mexican Gulf Coast?


Figure 2. Forecast swath of tropical storm force winds (34 - 63 knots, green colors) and hurricane force winds (yellow and orange colors) as predicted by this morning's 2am EDT run of the HWRF model. Image credit: Morris Bender, NOAA GFDL team.

The key question remains how Alex will react to the trough of low pressure expected to swing down over the Eastern U.S. on Monday. Some of yesterday's model runs predicted that this trough would be strong enough to pull Alex northwards through the oil slick region into the northern Gulf of Mexico coast. However, the models that were predicting this (the GFS, GFDL, and HWRF models) are all backing off on that prediction. It now appears likely that Alex will cross the Yucatan, emerge into the Gulf of Mexico, then slow down as the trough to its north weakens the steering currents in the Gulf of Mexico on Monday. By Tuesday, the influence of the trough will wane, high pressure will build in, and Alex will resume a west-northwest, or possibly a due west or west-southwest motion, towards the Texas/Mexico border region. Based on the current trends in the models, Alex's tropical storm force winds are likely to stay well south of the oil slick region (Figure 2.) I put the odds of Alex bringing tropical storm-force winds to the oil slick region at 10%. The most significant impact Alex will likely have on the oil slick region is to bring 2 - 4 foot swells that may wash oil over some of the containment booms. These swells will reach the oil slick region on Tuesday and Wednesday.

Continued intensification of Alex is likely today, up until landfall. It is a good thing the storm waited until last night to get organized; had it formed a day earlier, it could have easily been a hurricane in the Western Caribbean today. Once Alex emerges back into the Gulf of Mexico on Monday, it will likely take the storm at least 24 hours to get re-organized, particularly since the total ocean heat content is low for the 100-mile-wide stretch of water on the west side of the Yucatan Peninsula. Once Alex moves more than 100 miles from the Yucatan, total heat content of the ocean increases substantially, and Alex will have the opportunity to intensify significantly. Steering currents will be weak in the Gulf next week, and it appears that Alex will have time to intensify into a hurricane before making its second landfall along the South Texas/northern Mexico coast. Wind shear is expected to be light, and dry air not a significant impediment. Most of the models are calling for landfall on Wednesday, but I wouldn't be surprised to see this delayed until Thursday. I give Alex a 60% chance of becoming a hurricane in the Gulf of Mexico next week.

Elsewhere in the tropics
A tropical wave (Invest 94L) is a few hundred miles northeast of the northernmost Lesser Antilles Islands. This wave is producing a modest amount of heavy thunderstorm activity, and is passing beneath a trough of low pressure that is generating 30 - 40 knots of wind shear, and is not a threat to develop today. However, by Monday, the storm will be in a region of much lower wind shear, and NHC is giving the storm a 10% chance of developing into a tropical depression by Monday morning. None of the models currently develop 94L, but Bermuda should keep and eye on this system, as it will pass very close to the island on Tuesday.

Extreme heat wave in Africa and Asia continues to set all-time high temperature records
A withering heat wave of unprecedented intensity and areal covered continues to smash all-time high temperatures Asia and Africa. As I reported earlier this week, Kuwait, Saudi Arabia, Iraq, Chad, Niger, Pakistan, and Myanmar have all set new records for their hottest temperatures of all time over the past six weeks. The remarkable heat continued over Africa and Asia late this week. The Asian portion of Russia recorded its highest temperate in history yesterday, when the mercury hit 42.3°C (108.1°F) at Belogorsk, near the Amur River border with China. The previous record was 41.7°C (107.1°F) at nearby Aksha on July 21, 2004. (The record for European Russia is 43.8°C--110.8°F--set on August 6, 1940, at Alexandrov Gaj near the border with Kazakhstan.) Also, on Thursday, Sudan recorded its hottest temperature in its history when the mercury rose to 49.6°C (121.3°F) at Dongola. The previous record was 49.5°C (121.1°F) set in July 1987 in Aba Hamed.

We've now had eight countries in Asia and Africa, plus the Asian portion of Russia, that have beaten their all-time hottest temperature record during the past two months. This includes Asia's hottest temperature of all-time, the astonishing 53.5°C (128.3°F) mark set on May 26 in Pakistan. All of these records are unofficial, and will need to be certified by the World Meteorological Organization (WMO). According to Chris Burt, author of Extreme Weather, the only year which can compare is 2003, when six countries (the UK, France, Portugal, Germany, Switzerland, and Liechtenstein) all broke their all-time heat records during that year's notorious summer heat wave. Fortunately, the residents of the countries affected by this summer's heat wave in Asia and Africa are more adapted to extreme high temperatures, and we are not seeing the kind of death tolls experienced during the 2003 European heat wave (30,000 killed.) This week's heat wave in Africa and the Middle East is partially a consequence of the fact that Earth has now seen three straight months with its warmest temperatures on record, according to NOAA's National Climatic Data Center. It will be interesting to see if the demise of El Niño in May will keep June from becoming the globe's fourth straight warmest month on record.

Wind and ocean current forecast for the BP oil disaster
East to southeast winds of 5 - 15 knots will blow in the northern Gulf of Mexico today through Wednesday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should push the oil to the west and northwest onto portions of the Louisiana and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. I would expect Mississippi to have its most serious threat of oil yet early next week as these winds continue. The long range outlook shows a continuation of east to southeast winds along the northern Gulf of Mexico coast.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Wunderground's severe weather expert Dr. Rob Carver will likely be posting at least one update on Alex this weekend. My next update will be Sunday morning.

Jeff Masters

Hurricane

Updated: 05:06 PM GMT del 29 Giugno 2010

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Act I, Scene I, Tropical Depression One of the Hurricane Season of 2010

By: JeffMasters, 12:57 AM GMT del 26 Giugno 2010

Act I, Scene I, Tropical Depression One of the 2010 hurricane is at hand. The storm is already bringing heavy rains to northern Honduras, where 3.78" fell at Puerto Lempira, on the coast near the Nicaragua border. Recent satellite images show continued development of TD 1's heavy thunderstorm activity, and this depression appears to be a lock to intensify into Tropical Storm Alex by Saturday morning. I'll save a more detailed analysis for Saturday morning, and merely post some historical data on how similar storms have behaved over the past twenty years.

History of storms similar to TD 1
Dr. Jonathan Vigh of the National Center for Atmospheric Research has put together a brief synopsis of tropical cyclones (1989-2008) which formed near NW Honduras or east of Mexico's Yucatan Peninsula or developed while over the Yucatan, or storms which were already formed but later hit the Yucatan Peninsula. Storms which formed late in the season and recurved into Cuba were not examined. Out of the 19 storms which hit the Yucatan, 8 went on to make a second Gulf Coast landfall in Mexico, 5 hit the U.S. Gulf Coast, and 6 died after hitting the Yucatan. A few storms formed while over the Yucatan and went in various directions. He makes a few notes about how passage over the Yucatan changed the radius of maximum winds (RMW) of the storms.

Storms that hit the Yucatan, then hit Mexico on the west side of the Gulf of Mexico:
Diana 1990: Developed E of Nicaragua, hit Yucatan as tropical Storm (TS), hit near Tampico as a hurricane. Normal decrease in RMW during intensification to hurricane: RMW droped from ~40 n mi to 15 n mi.



Gert 1993: Traveled as TD over Nicaragua, became a TS and then hit Belize, hit near Tampico as a hurricane. RMW 30-35 n mi during intensification.

Roxanne 1995: Formed east of Nicauragua, hit near Cozumel as hurricane, did some loops and then died in Bay of Campeche. RMW dropped from 30 n mi to 10 n mi before first Yucatan hit, then became very large for a day or two, then contracted down to 3 n mi, then became large again (>50 n mi), then contracted once more before storm died. Was doing several loops in Bay of Compeche during this time.

Dolly 1996: Formed west of Jamaica, hit south of Cozumel as hurricane, then hit MX as a hurricane. RMW increased from 7 to 40 n mi before Yucatan landfall, then afterwards decreased to 13 n mi as the storm intensified before 2nd landfall.

Keith 2000: Developed off NE Honduras, hit Belize as major hurricane, weakened to TD, then redeveloped and hit MX coast as hurricane. RMW decreased to 9 n mi before the rapid intensification, then increased to about 25 nm mi before landfall. Increased to 30 n mi by second landfall.

Emily 2005: Hit Yucatan as major hurricane, hit S of Brownsville as a hurricane. RMW increased from ~10 n mi before landfall, to about 30 n mi after Yucatan crossing, then decreased back down to 10-15 n mi by second landfall.

Stan 2005: Formed just SE of Cozumel, hit near there as TS, weakend to TD then shifted S and hit Bay of Campeche coast as hurricane, caused massive flooding. After Yucatan crossing, RMW decreased from ~40 n mi to about 5 n mi before 2nd landfall - normal progression.

Dean 2007: through Caribbean as hurricane, hit just N of Belize as major hurricane, hit near Tampico as hurricane. RMW was about 13 n mi before Yucatan landfall, then >40 n mi after before shrinking to 28 n mi by 2nd landfall.

Storms that hit the Yucatan, then hit the U.S. Gulf Coast:
Isidore 2002: Hurricane south of Cuba, hit W tip of Cuba then deflected into N Yucatan, inner core wiped out, then hit LA as a gigantic TS. RMW ~7 n mi before
Yucatan landfall, then off the scale afterward.

Bill 2003: Formed after traveling over Yucatan, hit LA as TS. Large RMW dropped to 12 n mi by LA landfall.

Claudette 2003: TS south of Hispianola, grazed tip of Yucatan as TS, hit near Corpos Christi as hurricane. RMW increased to >40 n mi BEFORE Yucatan landfall, then dropped to 20 - 35 n mi range afterward.

Cindy 2005: Hit Yucatan as TD, became TS day later, hit LA as hurricane. Little data, but RMW was 15-30 n mi by landfall.



Wilma 2005: Spent about a day over Yucatan, weakened and became very large, but RMW was little changed: 30-35 n mi before and after (eventually with much larger outer RMW).

Storms which died after hitting the Yucatan:
TD 8 1994 Formed near NE Honduras coast, hit Belize, died

Kyle 1996 Hit Belize as TS, died.

Katrina 1999 Developed E of Nicaurgua, hit as TS, hit Belize as TD, died

Chantal 2001 TS across Caribbean, hit Yucatan, deflected southward and died.

Iris 2001 Hurricane across Caribbean, hit Belize and died.

Arthur 2008 Formed just before hitting Belize as TS, died.

Storms that developed over the Yucatan:
Opal 1995: Developed over Yucatan, underwent rapid intensification, got a tight inner core, then weakened and hit FL as major hurricane of normal size. RMW was actually very small (5 n mi) a day after coming off the Yucatan, but increased to be quite large (25-35 n mi) before the rapid intensification period commenced and brought it back down to 7 n mi. RMW increased rapidly to >40 n mi right before landfall.



Gordon 2000: Developed over Yucatan, became hurricane then hit FL as TS north of Tampa. RMW increased from 5 n mi before Yucatan landfall, to 40 n mi afterward, then decreased back to 3 n mi during the subsequent intensification. Made landfall with RMW of 35 n mi.

Larry 2003: Formed after crossing top of Yucatan, hit south shore of Bay of Campeche as TS, died.

Gert 2005: Formed in Bay of Campeche after traveling over Honduras and Yucatan, hit MX as TS.

Jeff Masters

Hurricane

Updated: 02:19 PM GMT del 27 Giugno 2010

Permalink

93L near tropical depression strength

By: JeffMasters, 02:31 PM GMT del 25 Giugno 2010

The first tropical depression of the 2010 Atlantic hurricane season appears imminent in the Western Caribbean, as the areal coverage and intensity of heavy thunderstorm activity associated with the tropical wave (Invest 93L) continue to increase. The storm has developed a surface circulation near 16.5N, 82.5W at 8am EDT, about 100 miles northeast of the Nicaragua/Honduras border. This is far enough from land that development will be slowed only slightly. Satellite loops show a poorly organized system, with only a modest amount of heavy thunderstorm activity near the center. However, the developing storm is affecting the weather across the entire Western Caribbean, and bands of heavy thunderstorms are quickly building over a large region. Pressures at ground stations and buoys all across the Western Caribbean have been falling significantly over the past day (Figure 2.) Water vapor satellite loops show that moist air surrounds 93L, and there is not much dry air to slow down development. There is an upper-level high pressure system a few hundred miles west of 93L, and the clockwise flow air around this high is bringing upper-level winds out of the northwest of about 10 - 15 knots over 93L, contributing to the 10 - 15 knots of wind shear observed in this morning's wind shear analysis from the University of Wisconsin's CIMSS group. Sea Surface Temperatures are very warm, 29 - 30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The main negative for 93L is a combination of lack of spin and wind shear. Last night's pass of the ASCAT satellite showed a broad, elongated circulation, which will need to tighten up in order for 93L to become a tropical depression. The Hurricane Hunters are scheduled to fly into 93L at 2pm EDT this afternoon to see if a tropical depression has formed.


Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.


Figure 2. Combined plot of wind speed, wind gusts, and pressure at buoy 42057 in the Western Caribbean. Pressure (green line) has fallen significantly over the past two days, and winds are beginning to increase.

Forecast for 93L
The greatest risk from 93L to the Western Caribbean will be heavy rainfall, and the nation most at risk is Honduras. The counter-clockwise flow of air around 93L will bring bands of rain capable of bringing 4 - 8 inches of rain to northern Honduras over the next two days. Heavy rains of 3 - 6 inches can also be expected in northeast Nicaragua, Cuba, Belize, the Cayman Islands, and Mexico's Yucatan Peninsula. The storm is moving west-northwest at about 10 mph, and this motion is expected to gradually slow over the next five days to about 6 mph. I expect that by tomorrow, 93L should be closer to being directly underneath the upper level high pressure system to its west, which would act to lower wind shear and provide more favorable upper-level outflow. NHC is giving 93L a 70% chance of developing into a tropical depression by Sunday morning, which is a reasonable forecast. The storm will probably be a tropical depression or tropical storm with 40 mph winds when it moves over Mexico's Yucatan Peninsula on Sunday. The storm will probably spend a day or so over the Yucatan, resulting in significant weakening. Once 93L emerges over the Gulf of Mexico, it will take the storm 24+ hours to recover its strength.

A trough of low pressure is expected to swing down over the Eastern U.S. on Monday. If this trough is strong enough and 93L develops significantly, the storm could get pulled northwards and make landfall along the northern Gulf of Mexico coast. This is the solution of the GFDL and HWRF models. If 93L stays weak and/or the trough is not so strong, the storm would get pushed west-northwestwards across Mexico's Bay of Campeche and make landfall along Mexican coast south of Texas, or in Texas. This is the solution of the NOGAPS, ECMWF, and Canadian models. A likely landfall location is difficult to speculate on at this point, and the storm could hit virtually anywhere along the Gulf of Mexico coast given the current uncertainty in its development. The amount of wind shear in the Gulf of Mexico next week is also highly uncertain. There is currently a band of high shear near 30 knots over the Gulf. The GFS model predicts that this band of high shear will lift northwards, keeping low wind shear over the Gulf next week. However, the ECMWF model keeps high shear entrenched over the Gulf of Mexico, which would make it unlikely 93L could intensify into a hurricane. In summary, I give 93L a 60% chance of eventually becoming Tropical Storm Alex, and 10% chance of eventually becoming a hurricane.

Elsewhere in the tropics
A tropical wave a few hundred miles northeast of the northernmost Lesser Antilles Islands is producing a modest amount of heavy thunderstorm activity. This system was designated Invest 94 by NHC this morning, and is passing beneath a trough of low pressure that is generating 30 - 40 knots of wind shear. However, by Sunday, the storm will be in a region of much lower wind shear, and NHC is giving the storm a 10% chance of developing into a tropical depression by Sunday morning. We do have one model, the GFS, which develops the system early next week. The GFS model takes the storm to the northwest and then north, predicting it will be very close to Bermuda on Tuesday.


Figure 3. Hurricane Celia as a Category 4 storm at 20:55 UTC Thursday, June 24, 2010, as captured by NASA's MODIS instrument.

Impressive Hurricane Celia hits Category 5
The first Category 5 hurricane in the Northern Hemisphere this year is Hurricane Celia in the Eastern Pacific. Celia's 160 mph winds make it tied with Australia's Tropical Cyclone Ului as the strongest tropical cyclone in the world so far in 2010. Celia has likely peaked in intensity, and is not expected to threaten any land areas.

Wind and ocean current forecast for the BP oil disaster
East to southeast winds of 5 - 15 knots will blow in the northern Gulf of Mexico today through Tuesday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should push the oil to the west and northwest onto portions of the Louisiana and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. I would expect Mississippi to have its most serious threat of oil yet early next week as these winds continue. The longer range outlook is uncertain, and will depend upon what 93L does.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Jeff Masters

Hurricane

Updated: 03:14 PM GMT del 25 Giugno 2010

Permalink

93L still disorganized; extreme heat wave hits the Middle East and Africa

By: JeffMasters, 02:05 PM GMT del 24 Giugno 2010

The amount and intensity of heavy thunderstorm activity associated with the tropical wave (Invest 93L) located a few hundred miles south of Jamaica has increased over the past 24 hours, but the storm remains very disorganized and is not a threat to develop into a tropical depression today. The storm has not brought heavy rains to Haiti, fortunately, but heavy rains are expected today across Jamaica, where flash flood warnings have been posted. Satellite loops show a very disorganized system, with no low-level spiral bands and limited upper-level outflow. There are no signs of a surface circulation visible on satellite imagery. Pressures at the ground station nearest to the storm (Kingston) are beginning to fall, as are pressures at buoy 42057 a few hundred miles west of the storm, a sign that 93L is more organized than yesterday. Water vapor satellite loops show that moist air surrounds 93L, and there is less dry air to the storm's southwest than there was yesterday. There is an upper-level high pressure system a few hundred miles west of 93L, and the clockwise flow air around this high is bringing upper-level winds out of the northwest of about 10 knots over 93L, contributing to the 10 knots of wind shear observed in this morning's wind shear analysis from the University of Wisconsin's CIMSS group. Sea Surface Temperatures are plenty warm, a record 29 - 30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The main negative for 93L continues to be the lack of spin. Last night's pass of the ASCAT satellite showed little in the way of a wind shift associated with 93L, though the pass did not completely capture the storm. The University of Wisconsin 850 mb relative vorticity analysis is showing that spin at 850 mb (roughly 5,000 feet in altitude) has increased over the past two days. The Hurricane Hunters are on call to investigate 93L Friday afternoon. Today's flight was canceled, due to 93L's lack of development.


Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.

Track forecast for 93L
I expect that by tomorrow, 93L should be closer to being directly underneath the upper level high pressure system to its west, which would act to lower wind shear and provide more favorable upper-level outflow. NHC is giving 93L a 40% chance of developing into a tropical depression by Saturday morning, which is a reasonable forecast. Given the storm's current lack of spin and relatively modest amount of heavy thunderstorms, the earliest I'd expect 93L to become a tropical depression would be Friday afternoon, with Friday night or Saturday morning more likely. Interaction with land will be a problem for 93L, as it will likely move over Mexico's Yucatan Peninsula or Western Cuba on Saturday. Expect 93L to bring flooding rains of 3 - 6 inches to Jamaica and eastern Cuba today through Friday. These rains will spread to the Cayman Islands, northern Honduras, and central Cuba Friday through Saturday, and western Cuba, Belize, and Mexico's Yucatan Peninsula on Saturday and Sunday. The current run of the SHIPS model has 93L slowing down late this week to a forward speed of just 7 knots (8 mph) from its current speed of about 10 mph, in response to a weakening in the steering currents. A trough of low pressure is expected to swing down over the Eastern U.S. on Monday. If this trough is strong enough and 93L develops significantly, the storm could get pulled northwards and make landfall along the northern Gulf of Mexico coast. This is the solution of the GFS, GFDL, and HWRF models. If 93L stays weak and/or the trough is not so strong, the storm would get pushed west-northwestwards across Mexico's Yucatan Peninsula and towards the Texas or Mexican coast south of Texas. This is the solution of the NOGAPS, ECMWF, and Canadian models. A likely landfall location is impossible to speculate on reliably at this point, and the storm could hit virtually anywhere along the Gulf of Mexico coast given the current uncertainty in its development. A key factor will be how far north the center of 93L eventually consolidates at.

Intensity forecast for 93L
The amount of wind shear in the Gulf of Mexico next week is highly uncertain. There is currently a band of high shear near 30 knots over the Gulf. The GFS model predicts that this band of high shear will lift northwards, keeping low wind shear over the Gulf next week. However, the ECMWF model keeps high shear entrenched over the Gulf of Mexico. I give 93L a 50% chance of eventually becoming Tropical Storm Alex, but the odds of it eventually becoming a hurricane have lessened to 10%. None of the computer models is calling for 93L to become a hurricane.

Elsewhere in the tropics
None of the reliable computer models is calling for tropical cyclone formation in the Atlantic over the next seven days.


Figure 2. Dust storm over Iraq on June 23, 2010. Image credit: NASA.

Extreme heat wave sets all-time high temperature records in Africa and Middle East
A withering heat wave of unprecedented intensity and areal covered has smashed all-time high temperatures in five nations in the Middle East and Africa over the past week. Saudi Arabia, Iraq, Chad, Kuwait, and Niger all set new records for their hottest temperatures of all time, and two other Middle East nations came within a degree of their hottest temperatures ever. The heat was the most intense in Kuwait, which recorded its hottest temperature in history on June 15 in Abdaly, according to information I received from the Kuwait Met office. The mercury hit 52.6°C (126.7°F). Kuwait's previous all-time hottest temperature was 51.9°C (125.4°F), on July 27,2007, at Abdaly. Temperatures reached 51°C (123.8°F) in the capital of Kuwait City on June 15, 2010.

Iraq had its hottest day in history on June 14, 2010, when the mercury hit 52.0°C (125.6°F) in Basra. Iraq's previous record was 51.7°C (125.1°F) set August 8, 1937, in Ash Shu'aybah.

It was also incredibly hot in Saudi Arabia, which had its hottest temperature ever on Tuesday (June 22): 52.0°C (125.6°F), measured in Jeddah, the second largest city in Saudi Arabia. The previous record was 51.7°C (125.1°F), at Abqaiq, date unknown. The record heat was accompanied by a sandstorm, which caused eight power plants to go offline, resulting in blackouts to several Saudi cities.

In Africa, Chad had its hottest day in history on Tuesday (June 22), when the temperature reached 47.6°C (117.7°F) at Faya. The previous record was 47.4°C (117.3°F) at Faya on June 3 and June 9, 1961.

Niger tied its record for hottest day in history on Tuesday (June 22), when the temperature reached 47.1°C (116.8°F) at Bilma. That record stood for just one day, as Bilma broke the record again on Wednesday (June 23), when the mercury topped out at 48.2°C (118.8°F). The previous record was 47.1°C on May 24, 1998, also at Bilma.

Two other countries came within a degree of their all time hottest temperature on record during the heat wave. Bahrain had its hottest June temperature ever, 46.9°C, on June 20, missing the all-time record of 47.5°C (117.5°F), set July 14, 2000. Temperatures in Quatar reached 48.8°C (119.8°F) on June 20. Quatar's all-time record hottest temperature was 49.6°C (121.3°F) set on July 9, 2000.

According to Essa Ramadan, a Kuwaiti meteorologist from Civil Aviation, Matrabah, Kuwait smashed this record and had Asia's hottest temperature in history on June 15 this year, when the mercury hit 54.0°C (129.2°F). However, data from this station is notoriously bad, and each year bogus record highs have to be corrected, according to an email I received from weather record researcher Maximiliano Herrera. Asia's hottest temperature in history will very likely remain the 53.5°C (128.3°F) recorded at MohenjuDaro, Pakistan on May 26 this year.

Commentary
We've now had seven countries in Asia and Africa that have beaten their all-time hottest temperature record during the past two months. As I discussed in my blog about Pakistan's May 26 record, Southeast Asia also had its all-time hottest temperature in May, when the mercury hit 47°C (116.6°F) in Myinmu, Myanmar on May 12. All of these records are unofficial, and will need to be certified by the World Meteorological Organization (WMO). According to Chris Burt, author of Extreme Weather, setting five national heat records in one month is not unprecedented--in August 2003, six countries (the UK, France, Portugal, Germany, Switzerland, and Liechtenstein) all broke their all-time heat records during that year's notorious summer heat wave. Fortunately, the residents of the countries affected by this week's heat wave are more adapted to extreme high temperatures, and we are not seeing the kind of death tolls experienced during the 2003 European heat wave (30,000 killed.) This week's heat wave in Africa and the Middle East is partially a consequence of the fact that Earth has now seen three straight months with its warmest temperatures on record, according to NOAA's National Climatic Data Center. It will be interesting to see if the demise of El Niño in May will keep June from becoming the globe's fourth straight warmest month on record.


Figure 3. Approximate oil spill location on June 23, 2010, and estimated by NOAA using visible satellite imagery from NASA's MODIS instrument, and Synthetic Aperture Radar (SAR) imagery from polar-orbiting satellites. Image credit: NOAA Satellite Services Division.

Wind and ocean current forecast for the BP oil disaster
East to southeast winds of 5 - 15 knots will blow in the northern Gulf of Mexico today through Monday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should push the oil to the west and northwest onto portions of the Louisiana and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. I would expect Mississippi to have its most serious threat of oil yet early next week as these winds continue. The longer range outlook is uncertain, and will depend upon what 93L does.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Jeff Masters

Heat Hurricane

Updated: 05:02 PM GMT del 29 Giugno 2010

Permalink

Little change to 93L; Brazilian floods kill 42

By: JeffMasters, 02:18 PM GMT del 23 Giugno 2010

There has been little change over the past 24 hours to the tropical wave (Invest 93L) located a few hundred miles south of Haiti. The storm has brought heavy rains to the waters south of Hispaniola, with radar precipitation estimates from the Puerto Rico radar of over six inches of rain in the past day. The heaviest rains have avoided land areas so far. Satellite loops show a very disorganized system, with no low-level spiral bands and only limited heavy thunderstorm activity. There are no signs of a surface circulation visible on satellite imagery. Pressures at the ground stations surrounding the storm (Bahahona and Kingston) are not falling. Water vapor satellite loops show that moist air surrounds 93L, though there is a modest patch of dry air to the storm's southwest. This dry air is likely contributing to the lack of heavy thunderstorms on 93L's west side, slowing development. Wind shear is a low 5 - 15 knots. The high wind shear associated with the strong winds of the subtropical jet stream are over the northern Caribbean, too far north to interfere with development, but close enough to provide good upper-level outflow for the storm. Visible satellite loops show high level cirrus clouds streaming away from 93L to the northeast, evidence of the upper-level outflow channel that is developing to the storm's north. Sea Surface Temperatures are plenty warm, a record 29 - 30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The main negative for 93L continues to be the lack of spin. The University of Wisconsin 850 mb relative vorticity analysis is showing that spin at 850 mb (roughly 5,000 feet in altitude) has increased over the past day, but 93L needs to acquire additional spin before it can grow more organized. The Hurricane Hunters are on call to investigate 93L Thursday afternoon. Today's flight was canceled, due to 93L's lack of development.


Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.

Track forecast for 93L
NHC is giving 93L a 30% chance of developing into a tropical depression by Friday morning, which is a reasonable forecast. Given the storm's current lack of spin and relatively modest amount of heavy thunderstorms, the earliest I'd expect 93L to become a tropical depression would be Thursday afternoon, with Friday more likely. Wind shear is expected to be low, less than 10 knots, over the central and western Caribbean this week. Water temperatures will be warm, dry air limited, and the MJO favorable. I don't see any major impediments to the storm becoming a tropical depression by Friday, except for possible interaction with land. There is a low (less than 20% chance) of 93L becoming a hurricane in the Caribbean. Expect 93L to bring flooding rains of 3 - 6 inches to Jamaica, eastern Cuba, and southwestern Haiti today through Thursday. These rains will spread to the Cayman Islands and central Cuba by Thursday through Friday, and western Cuba and Mexico's Yucatan Peninsula on Friday and Saturday. The current run of the SHIPS model has 93L slowing down late this week to a forward speed of just 7 knots (8 mph) from its current speed of about 10 mph, in response to a weakening in the steering currents. A trough of low pressure is expected to swing down over the Eastern U.S. on Monday. If this trough is strong enough and 93L develops significantly, the storm could get pulled northwards and make landfall along the northern Gulf of Mexico coast. This is the solution of the ECMWF, GFDL, and HWRF models. This seems like a likely solution, since recent runs of most of the models have been showing a stronger trough. If 93L stays weak and/or the trough is not so strong, the storm would get pushed west-northwestwards towards the Texas coast. This is the solution of the NOGAPS and Canadian models, which foresee a more westerly track for 93L across the Yucatan Peninsula, with the storm eventually threatening Texas by Monday or Tuesday. The GFS and UKMET models do not develop 93L. A likely landfall location is highly uncertain this point, and the storm could hit virtually anywhere along the Gulf of Mexico coast from South Texas to the Florida Panhandle given the current uncertainty in its development, and the strength of next Monday's trough that may steer 93L northwards.

Intensity forecast for 93L
Forecasting the amount of wind shear in the Gulf of Mexico next week is problematic. There is currently a band of high shear near 30 knots over the Gulf, and most of the models predict that this band of high shear will lift northwards, keeping low wind shear over the Gulf next week. This should allow 93L to intensify to at least a 50 mph tropical storm, as predicted by the HWRF model. The GFDL and ECMWF models are calling for 93L to become a Category 1 or 2 hurricane, and this is certainly a possibility. I expect 93L will become Tropical Storm Alex in the Gulf of Mexico next week, and give a 20% chance that it will become a hurricane.

Elsewhere in the tropics
None of the reliable computer models is calling for tropical cyclone formation in the Atlantic over the next seven days.


Figure 2. Total accumulated precipitation in millimeters (left) for the 7-day period ending at 8am EDT June 21, 2010. The yellow colors (200+ mm, 8+ inches) are where extreme flooding was observed. Satellite image from NASA's MODIS instrument (right) for June 17, 2010, showing heavy thunderstorms over the Alagoas state of Brazil. Image credit: NASA and NOAA Climate Prediction Service.

Floods in Brazil kill dozens
Heavy rains over the past week in the northeast state of Alagoas in Brazil have led to major flooding that has killed at least 42 people. Six hundred people are still missing. This weekend rains in Alagoas and Pernambuco states are the latest in a series of devastating floods to strike Brazil this year. Since the start of Brazil's rainy season last November, 488 people have been killed by flooding and 7.5 million have been affected in 10 states. Much of the heavy rains can be blamed on El Niño, which ended in May. In April, flooding and landslides triggered by torrential rain killed at least 229 people and did $13.3 billion in damage in the Rio de Janeiro area.

It's been a bad year for floods, and there are two other major flooding disasters that have occurred in the past week. In China, the death toll has risen to 211 people, with 119 people missing, because of flooding in the southern portion of the country. France suffered a flash flood last week that killed 25.

Wind and ocean current forecast for the BP oil disaster
East to southeast winds of 10 - 15 knots will blow in the northern Gulf of Mexico today through Sunday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should push the oil to the west and northwest onto portions of the Louisiana and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. I would expect Mississippi to have its most serious threat of oil yet early next week as these winds continue. The longer range outlook is uncertain, and will depend upon what 93L does.

Resources for the BP oil disaster
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool allows one to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Jeff Masters

Flood Hurricane

Updated: 10:29 PM GMT del 03 Gennaio 2012

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93L slow to develop, but bringing heavy rains to Haiti

By: JeffMasters, 01:50 PM GMT del 22 Giugno 2010

A modest region of intense thunderstorms (Invest 93L) is over the central Caribbean, a few hundred miles south of Hispaniola. This disturbance has the best chance to become Tropical Storm Alex of any system we've seen so far this year. We don't have any buoys near 93L, but pressures at the ground stations surrounding the storm are not falling. A pass of the ASCAT satellite over the Central Caribbean at 9:45 pm EDT last night revealed a modest wind shift associated with 93L, but nothing at all close to a surface circulation. Top surface winds seen by ASCAT were 15 - 20 mph. Water vapor satellite loops show that 93L is embedded in a large region of moist air. The atmosphere over the Caribbean has moistened over the past day, which should aid development of 93L. Wind shear is a low 5 - 10 knots. The high wind shear associated with the strong winds of the subtropical jet stream are over the northern Caribbean, too far north to interfere with development, but close enough to provide good upper-level outflow for the storm. Visible satellite loops show high level cirrus clouds streaming away from 93L to the northeast, evidence of the upper-level outflow channel that is developing to the storm's north. Sea Surface Temperatures are plenty warm, a record 29 - 30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The main negative for 93L continues to be lack of spin. The University of Wisconsin 850 mb relative vorticity analysis is showing that spin at 850 mb (roughly 5,000 feet in altitude) has increased over the past day, but 93L needs to acquire additional spin before it can grow more organized. I speculate that it is this lack of spin that contributed to the loss of much of 93L's heavy thunderstorm activity last night. The storm is now going through a cycle where it is building another respectable mass of heavy thunderstorms, and the increased inflow of low-level air that will feed these thunderstorms will likely enhance 93L's spin today. The Hurricane Hunters are on call to investigate 93L on Wednesday afternoon.


Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.

Forecast for 93L
NHC is giving 93L a 40% chance of developing into a tropical depression by Thursday morning, which is a reasonable forecast. Given the storm's current lack of spin and relatively modest amount of heavy thunderstorms, the earliest I'd expect 93L to become a tropical depression would be Wednesday afternoon, with Thursday more likely. Wind shear is expected to be low, less than 10 knots, over the central and western Caribbean this week. Water temperatures will be warm, dry air absent, and the MJO favorable. I don't see any major impediments to the storm becoming a tropical depression by Thursday, and it is a bit of a surprise to me that the computer models have been reluctant to develop 93L. The GFS, NOGAPS, and UKMET models do not develop 93L, and the ECMWF model doesn't develop 93L until after it crosses the Yucatan Peninsula and enters the Gulf of Mexico in a about a week. The current (2am EDT) run of the GFDL model predicts 93L will be a weak tropical storm in the Gulf of Mexico in five days; its previous run had 93L as a major hurricane in the Gulf. Given all this model reluctance and the current disorganization of 93L, I give the storm a low (less than 20% chance) of becoming a hurricane in the Caribbean. Expect 93L to bring flooding rains of 3 - 6 inches to Jamaica, eastern Cuba, and southwestern Haiti today through Wednesday. These rains will spread to the Cayman Islands and central Cuba by Thursday, and western Cuba and Mexico's Yucatan Peninsula on Friday. The current run of the SHIPS model has 93L slowing down late this week to a forward speed of just 6 knots (7 mph) from its current speed of about 10 mph, in response to a weakening in the steering currents. A trough of low pressure is expected to swing down over the Eastern U.S. early next week. If this trough is strong enough and 93L develops significantly, the storm could get pulled northwards and make landfall along the northern Gulf of Mexico coast in the oil spill region. This is the solution of the Canadian GEM model. If 93L stays weak and/or the trough is not so strong, the storm would get pushed west-northwestwards towards the Texas coast. This is the solution of the ECMWF model. The amount of wind shear in the Gulf of Mexico next week is highly uncertain. There is currently a band of high shear near 30 knots over the Gulf, and some of the models predict this shear will remain over the Gulf over the next 7 - 10 days. However, other models predict that this band of high shear will retreat northwards and leave the Gulf nearly shear-free. The long-term fate of 93L remains very murky. My main concerns at this point are the potential for 3 - 6 inches of rain in Haiti over the next two days, and the possibility 93L could become a hurricane in the Gulf of Mexico next week.

Elsewhere in the tropics
None of the reliable computer models is calling for tropical cyclone formation elsewhere in the Atlantic over the next seven days.

Floods in China and Burma kill over 250
The deadliest and most destructive weather-related disaster on the planet so far this year is occurring in southern China and northern Burma, where a week of heavy rains has caused flooding that has claimed over 250 lives. The heavy rains and floods ravaging 10 southern Chinese provinces had killed 199 and left 123 missing as of 11:00 a.m. Tuesday, a Ministry of Civil Affairs statement said. Damage is estimated at $6.2 billion. Floods and landslides in neighboring areas of Myanmar (Burma) have claimed at least 63 lives in the past week.


Figure 2. Paramilitary policemen help evacuate residents from Wanjia village of Fuzhou City, East China's Jiangxi province, June 22, 2010. Days of heavy rain burst the Changkai Dike of Fu River on June 21, threatening the lives of 145,000 local people. Local authorities have ordered immediate evacuation, and the army and paramilitary police have begun conducting rescue operations. Image credit: Xinhua.

Wind and ocean current forecast for the BP oil disaster
Southeast to east winds less than 10 knots will blow in the northern Gulf of Mexico today through Saturday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should cause little motion of the oil slick, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range outlook is uncertain, and will depend upon what 93L does.

Resources for the BP oil disaster
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool allows one to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) The latest on 93L
2) Which model is the most reliable?

Today's show will be 30 - 40 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

Hurricane

Updated: 10:29 PM GMT del 03 Gennaio 2012

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New Caribbean disturbance 93L a major concern; flooding in Asia kills over 200

By: JeffMasters, 02:50 PM GMT del 21 Giugno 2010

A concentrated region of intense thunderstorms associated with a tropical wave has developed in the central Caribbean, a few hundred miles south of Puerto Rico. This disturbance was designated Invest 93L by NHC this morning, and has the best chance to become Tropical Storm Alex of any system we've seen so far this year. The disturbance is located near Buoy 42059, and this buoy has been reporting winds of 5 - 15 knots this morning. So far, pressures are not falling. Water vapor satellite loops show that 93L is embedded in a large region of moist air. Some dry continental air from North America is over the western Caribbean, but this dry air is too far away to interfere with development today and Tuesday. Wind shear is a low 5 - 10 knots. The high wind shear associated with the strong winds of the subtropical jet stream are over the northern Caribbean, too far north to interfere with development. Sea Surface Temperatures are plenty warm, a record 29 - 30°C. The Madden-Julian oscillation currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The only negative for 93L would seem to be the lack of spin; the University of Wisconsin 850 mb relative vorticity analysis is showing only meager amounts of spin at 850 mb (roughly 5,000 feet in altitude.)


Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.

Forecast for 93L
NHC is giving 93L a 20% chance of developing into a tropical depression by Wednesday morning, which is a reasonable forecast. With wind shear expected to drop to low values less than 10 knots over the central and western Caribbean this week (Figure 2), I don't see any major impediments to the storm becoming a tropical depression by Friday. The ECMWF model is the most aggressive in developing this system, taking it into the Gulf of Mexico as a hurricane next week. The NOGAPS model keeps the storm weak and farther south, predicting that 93L will bring heavy rains to northern Honduras as a tropical disturbance or tropical depression on Friday and Saturday. The GFS model does not develop 93L. Expect 93L to bring flooding rains of 3 - 6 inches to Jamaica, eastern Cuba, and extreme southwestern Haiti on Wednesday. These rains will spread to the Cayman Islands and central Cuba by Thursday.


Figure 2. Predicted wind shear for Friday, June 25, as forecast by this morning's 2am EDT run of the GFS model. Shear is given in meters per second; multiply by about two to convert to knots. Low wind shear values less than 6 m/s (12 knots) are predicted for much of the Western Caribbean this week.

Elsewhere in the tropics
The tropical wave (92L) that brought heavy rains of 2 - 5 inches to Puerto Rico on Saturday has weakened and is no longer a threat to bring flooding rains to the Caribbean.

Floods in China and Burma kill over 200
The deadliest and most destructive weather-related disaster on the planet so far this year is occurring in southern China and northern Burma, where a week of heavy rains has caused flooding that has claimed over 200 lives. The death toll stands at 175 in China and 63 in Burma, with more than 100 people still missing in China. Damage so far in China has been estimated at $4.3 billion.


Figure 3. Tree branches hung on a bridge at Taining County, southeast China's Fujian Province, June 19, 2010. Taining recorded 225 mm (9 inches) of rain in six hours on Friday. Image credit: Xinhua/Jiang Kehong.

Montana tornado rips roof off entertainment complex
A EF-2 tornado with winds of at least 100 mph ripped the roof of an entertainment complex in Billings, Montana on Sunday, causing up to $15 million in damage. No injuries were reported. It was the strongest tornado to hit the Billings area since 1958.


Figure 4. Video of the Billings tornado shows an impressive debris cloud (and a few expletives not deleted!) The clear slot on the right of the tornado is likely associated with the parent thunderstorm's rear flank downdraft.

Wind and ocean current forecast for the BP oil disaster
Southeast to east winds less than 10 knots will blow in the northern Gulf of Mexico today through Friday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should cause little motion of the oil slick, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range outlook is uncertain, as the tropical wave over the central Caribbean could enter the Gulf of Mexico early next week and develop into a tropical storm.

Resources for the BP oil disaster
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool allows one to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Jeff Masters

Flood Hurricane

Updated: 04:39 PM GMT del 21 Giugno 2010

Permalink

Tropical wave 92L weakens but could bring heavy rains to Haiti

By: JeffMasters, 02:23 PM GMT del 20 Giugno 2010

The tropical wave (92L) that brought heavy rains of 2 - 5 inches to Puerto Rico on Saturday is continuing westward at 10 - 15 mph, but has grown very disorganized. The National Hurricane Center is no longer interested enough in this wave to classify it as an "invest" worthy of generating computer forecasts for. Today through Monday, 92L will encounter 20 - 40 knots of wind shear as it plows though a region of strong upper-level winds associated with the subtropical jet stream. The disturbance will also encounter the mountainous terrain of Hispaniola and Cuba. If there is anything left of 92L after crossing these mountains, it may have the opportunity to develop beginning on Tuesday, when it will enter a region of wind shear less than 20 knots near central Cuba. None of our reliable computer forecast models is calling for 92L to develop once it reaches this region of lower wind shear. I give 92L a 10% chance of developing into a tropical depression by Saturday. The storm could bring heavy rains of up to four inches to Haiti today and Monday. Rain of four inches are probably the lower threshold for life-threatening floods to occur in the Haiti earthquake zone, and this disturbance poses the most serious flooding threat Haiti has seen since the earthquake.


Figure 1. Radar estimated rainfall over Puerto Rico from Invest 92L.

Elsewhere in the tropics
The NOGAPS and ECMWF models call for a possible tropical depression to form in the central or western Caribbean next weekend, 6 - 8 days from now.

Wind and ocean current forecast for the BP oil disaster
Southeast to east winds less than 10 knots will blow in the northern Gulf of Mexico Monday through Thursday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should cause little motion of the oil slick, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range outlook calls for a continued summertime weather pattern of weak winds over the Gulf of Mexico during the coming two weeks.


Figure 2. Visible satellite image from NASA's MODIS instrument of the Deepwater Horizon oil slick from Saturday, June 19, 2010.

Resources for the BP oil disaster
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool allows one to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Happy Father's Day, all you fathers out there, and I'll have an update on Monday.

Jeff Masters

Hurricane

Permalink

92L drenches Puerto Rico, and could develop into a TD by Wednesday

By: JeffMasters, 04:32 PM GMT del 19 Giugno 2010

Invest 92L continues its steady march to the west-northwest across the northern Caribbean. The storm has brought up to 4 inches of rain to Puerto Rico today, and will spread heavy rains of up to four inches over the Dominican Republic tonight and Haiti on Sunday. Rains of four inches are probably the lower threshold for life-threatening floods to occur in the Haiti earthquake zone, and this disturbance poses the most serious flooding threat Haiti has seen since the earthquake. There is no evidence of a surface circulation apparent on visible satellite imagery or surface observations. Water vapor satellite loops show that there is a large amount of dry, continental air from North America in the storm's environment. With wind shear at 30 - 40 knots today and expected to be 20 - 30 knots on Sunday, 92L is not a threat to develop into a tropical depression today or Sunday. The National Hurricane Center is giving 92L a low (10% chance) of developing into a tropical depression by Monday morning, which is a reasonable forecast. You can track the progress of 92L today by looking at our wundermap for the region, with weather stations turned on.


Figure 1. Radar estimated rainfall over Puerto Rico from Invest 92L.

92L could develop by Wednesday
Today through Monday, 92L will encounter 20 - 40 knots of wind shear as it plows though a region of strong upper-level winds associated with the subtropical jet stream. The disturbance will also encounter the mountainous terrain of Hispaniola and Cuba, though it appears that much of the disturbance's energy is tracking almost due west, and thus may escape disruption by these islands. If 92L manages to hold together through the high wind shear, dry air, and mountainous terrain of Hispaniola and Cuba, it may have the opportunity to develop beginning on Tuesday, when it may enter a region of wind shear less than 20 knots in the region near central Cuba. Some modest moistening of the atmosphere may also occur at that time, according to the latest SHIPS model run. The latest 12Z GFS model run indicates re-organization of 92L may occur by Wednesday over the waters near the Lower Florida Keys, but the ECMWF, NOGAPS, and UKMET models do not show this. The obstacles that 92L must overcome to become a tropical depression in the Gulf of Mexico next week are significant, and I give 92L a 20% chance of developing into a tropical depression by Friday.

Elsewhere in the tropics
The NOGAPS model is calling for a possible tropical depression to form in the central Caribbean on Friday.

Wind and ocean current forecast for the BP oil disaster
Light and variable winds less than 10 knots will blow in the northern Gulf of Mexico for the next four days, according to the latest marine forecast from NOAA. The winds will tend to have an offshore northerly component through Sunday, and an easterly component beginning on Monday. The resulting ocean currents should keep the oil near the coast from Alabama to Panama City, Florida, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Ocean current forecasts for the period Monday - Wednesday show only weak flow, which would result in little transport of oil from its current location. The long range 5+ day outlook is uncertain, as we will have to see what Invest 92L does once it reaches the western Caribbean and southern Gulf of Mexico on Wednesday. If the GFS model is correct, we can expect 92L to bring strong easterly winds to the oil spill location late next week, pushing the oil towards Louisiana.


Figure 2. Visible satellite image from NASA's MODIS instrument of the Deepwater Horizon oil slick from Friday, June 18, 2010.

Resources for the BP oil disaster
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool allows one to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll have an update on Sunday or Monday.

Jeff Masters

Hurricane

Updated: 02:12 AM GMT del 20 Giugno 2010

Permalink

92L very disorganized, but a long-range threat to develop

By: JeffMasters, 02:05 PM GMT del 18 Giugno 2010

Invest 92L, which yesterday became severely disrupted by wind shear and dry air, is generating a large area of rain showers over the northern Lesser Antilles Islands today. Infrared satellite loops show that the tops of the thunderstorms associated with 92L have warmed in recent hours, and these thunderstorms are weak and disorganized. Water vapor satellite loops show that there is a large amount of dry air in the storm's environment, and this dry air is getting sucked into 92L's thunderstorms, where the dry air is sinking to the surface and creating surface "arc clouds"--arc-shaped clouds that spread out away from 92L's thunderstorms. With wind shear at 20 - 30 knots today, no signs of a surface circulation, and plenty of dry air around, 92L is not a threat to develop into a tropical depression today or Saturday. The National Hurricane Center is giving 92L a low (20% chance) of developing into a tropical depression by Sunday morning. I put the chances at 1%. You can track the progress of 92L today by looking at our wundermap for the region, with weather stations turned on. Antigua recorded sustaiined winds of 20 mph this morning from 92L.

A slight chance 92L could develop next week
Today and Saturday, 92L will encounter 20 - 40 knots of wind shear as it plows though a region of strong upper-level winds associated with the subtropical jet stream. The disturbance will also encounter the mountainous terrain of Hispaniola. These factors should significantly disrupt the disturbance. If there's anything left of 92L by Sunday, when it will be over eastern Cuba, the storm may have the opportunity to develop. At that time, 92L will have passed through the core of the subtropical jet stream and entered a region of lower shear (15 - 20 knots.) For the latest round of 00Z and 06Z model runs, the HWRF is the only reliable model calling for 92L to develop; that model predicts that 92L will organize into a tropical depression on Wednesday over the Lower Florida Keys, and head into the Gulf of Mexico. The obstacles that 92L must overcome to do this are great, and I give 92L just a 10% chance of eventually developing into a tropical depression by Wednesday next week.


Figure 1. Morning satellite image of Invest 92L. Dry air is getting sucked into 92L's thunderstorms, where the more dense dry air creates downdrafts. When these downdrafts hit the surface, the air spreads out creating surface "arc clouds"--arc-shaped clouds that spread out away from 92L's thunderstorms. This puts stable air into the storm's low level environment and blocks inflow of moist air into the core of the storm, weakening it. These arc clouds are a telltale sign that dry air is significantly disrupting the disturbance.

Elsewhere in the tropics
The NOGAPS model is calling for a tropical disturbance to form off the coast of Nicaragua on Monday and push ashore over that country on Tuesday, bringing heavy rains.

Wind and ocean current forecast for the BP oil disaster
Light and variable winds less than 10 knots will blow in the northern Gulf of Mexico for the next five days, according to the latest marine forecast from NOAA. The winds will tend to have a westerly component through Saturday, which will maintain a threat of oil hitting beaches as far east as Panama City, Florida, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Ocean current forecasts for early next week show a weakening of the eastward-flowing currents along the Florida Panhandle, which would limit the eastward movement of oil so that it would not move past Panama City. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks.

Resources for the BP oil disaster
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's new interactive mapping tool allows one to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll have an update on Saturday.

Jeff Masters

Hurricane

Permalink

Globe has 3rd consecutive warmest month on record

By: JeffMasters, 01:24 PM GMT del 17 Giugno 2010

The globe recorded its warmest May since record keeping began in 1880, according to the National Oceanic and Atmospheric Administration's (NOAA's) National Climatic Data Center (NCDC). The May temperature anomaly of 0.69°C (1.24°F) beat the previous record set in 1998 by 0.06°C. We've now had three consecutive warmest months on record, the first time that has happened since 1998. NASA's Goddard Institute for Space Studies also rated May 2010 as the warmest May on record, tied with May 1998. Both NOAA and NASA rated the year-to-date period, January - May, as the warmest such period on record, and the last 12-month period (June 2009 - May 2010) as the warmest 12-month period on record. May 2010 global ocean temperatures were the second warmest on record, while land temperatures were the warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the 2nd warmest on record in May, according to both the University of Alabama Huntsville (UAH) and Remote Sensing Systems (RSS) groups.

For those interested, NCDC has a page of notable weather highlights from May 2010.


Figure 1. Departure of temperature from average for May 2010. Image credit: NOAA National Climatic Data Center (NCDC).

Asia and Southeast Asia record their hottest temperatures in history
The mercury hit an astonishing 53.5°C (128.3°F) at MohenjuDaro, Pakistan, on May 26. Not only is the 128.3°F reading the hottest temperature ever recorded in Pakistan, it is the hottest reliably measured temperature ever recorded on the continent of Asia. The evidence for this record is detailed in a post I made earlier this month. The Pakistan heat wave killed at least 18 Pakistanis, and temperatures in excess of 50°C (122°F) were recorded at nine Pakistani cities on May 26, including 53°C (127.4°F) at Sibi. Record heat also hit Southeast Asia in May. According to the Myanmar Department of Meteorology and Hydrology, Myanmar (Burma) had its hottest temperature in its recorded history on May 12, when the mercury hit 47°C (116.6°F) in Myinmu. Myanmar's previous hottest temperature was 45.8°C (114.4°F) at Minbu, Magwe division on May 9, 1998. According to Chris Burt, author of Extreme Weather, the 47°C (116.6°F) measured on May 12 this year is the hottest temperature measured in Southeast Asia in recorded history.

An average May for the U.S.
For the contiguous U.S., it was the 50th coldest (66th warmest) May in the 116-year record, according to the National Climatic Data Center. Idaho had its second coolest May on record, while it was Montana's fourth coolest, Wyoming's and Oregon's seventh coolest, Utah's eighth, California's ninth, and Nevada's tenth coolest such period. Rhode Island observed its second warmest May on record and Florida tied for its second warmest. Other states much warmer than normal during May included: Louisiana (4th warmest), Massachusetts (5th warmest), Connecticut (6th warmest), New Hampshire (7th warmest), Mississippi and New York (each 8th warmest), and New Jersey (9th warmest).

NCDC's Climate Extremes Index (CEI) for spring (March-May) was about 5 percent higher than average. The CEI measures the prevalence of several types of climate extremes (like record or near-record warmth, dry spells, or rainy periods). Factors contributing to spring's elevated values: widespread (2-3 times larger than average) coverage of anomalously warm daily max and min temperatures, and above-average extent of extreme one-day precipitation events. According to NOAA's Storm Prediction Center, tornadic activity in May was near normal with 290 preliminary tornado reports.

U.S. precipitation and drought
For the contiguous U.S., May 2010 ranked as the 35th wettest May in the 116-year record. The state of Washington had its third wettest May on record and extreme precipitation events in Tennessee and Kentucky contributed to their sixth and seventh wettest such period, respectively. It was the tenth wettest May in North Dakota. At the end of May, approximately 3% of the contiguous United States was in severe-to-exceptional drought. This is a very low amount of drought for the U.S.

La Niña likely by July
El Niño rapidly dissipated in May, with sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", falling to 0.50°C below average by June 14, according to NOAA.. The Australian Bureau of Meteorology is reporting that this number was 0.31°C below average (as of June 13.) Since La Niña conditions are defined as occurring when this number reaches 0.50°C below average, we are right at the threshold of a La Niña. NOAA's Climate Prediction Center has issued a La Niña watch, and it is likely that a full-fledged La Niña will emerge by July. Ten of the 23 El Niño models (updated as of May 19) are predicting La Niña conditions for hurricane season. However, as NOAA's Climate Prediction Center commented in their June 3 advisory, a number of the more reliable models are now calling for La Niña to develop this summer. They comment, "there is an increasing confidence in these colder model forecasts, which is supported by recent observations that show cooling trends in the Pacific Ocean and signs of coupling with the atmospheric circulation."

It is interesting to note that the last time we had a strong El Niño event, in 1998, El Niño collapsed dramatically in May, and a strong La Niña event developed by hurricane season. History appears to be repeating itself, and the emergence of La Niña will likely occur by July. The demise of El Niño, coupled with sea surface temperatures in the tropical Atlantic that are currently at record levels, suggest that a much more active Atlantic hurricane season that usual likely in 2010. The 1998 Atlantic hurricane season was about 40% above average in activity, with 14 named storms, 10 hurricanes, and 3 intense hurricanes. The season was relatively late-starting, with only one named storm occurring before August 20.


Figure 2. Ice extent through June 15, 2010 in the Arctic, compared to the record low years of 2006 and 2007. Record low Arctic ice extent began about June 1, and has remained at record low extent for the first half of June. Image credit: National Snow and Ice Data Center.

Arctic sea ice extent reaches a record low at end of May
Northern Hemisphere sea ice extent in May 2010 was the 9th lowest since satellite records began in 1979, according to the National Snow and Ice Data Center. Ice extent was near average at the beginning of May, but thanks to the fastest rate of decline ever observed during the month of May (50% faster than average), ice extent reached a record low by the end of May. Ice extent has remained at record low levels throughout the first half of June, as well. Ice volume was also at a record low at the end of May, according to University of Washington Polar Ice Center, due to the fact the Arctic is now dominated by thin first and second-year ice.

Record low Northern Hemisphere snow extent in May
For the second consecutive month, the Rutgers Snow Lab reported that the snow cover footprint over North America was the smallest on record for the month. A record-small snow footprint was also observed over Eurasia and the Northern Hemisphere as a whole.

The Atlantic is quiet
The 92L low pressure system, now located about 300 miles east of the northern Lesser Antilles Islands, has been completely disrupted by wind shear and dry air, and is no longer a threat to develop. The remnants of 92L, which are currently kicking up some strong thunderstorms due to interaction with an upper-level trough of low pressure, will bring heavy rain showers and wind gusts up to 35 mph to the northern Lesser Antilles Islands tonight through Friday, and into Puerto Rico Friday night through Saturday. On Sunday, the disturbance could bring heavy rains to northern Haiti. The earthquake zone in southern Haiti may also receive heavy enough rains to be of concern for the 1.5 million people living in tents and under tarps.

None of the reliable computer models is predicting formation of a tropical cyclone in the Atlantic over the next seven days, though the GFS model was suggesting a weak development moving through the southern Lesser Antilles Islands seven days from now.

Oil spill wind and ocean current forecast
Light and variable winds less than 10 knots will blow in the northern Gulf of Mexico for the next five days, according to the latest marine forecast from NOAA. The winds will tend to have a westerly component through Sunday, which will maintain a slow (1/4 mph) eastward-moving surface ocean current that will transport oil eastwards along the Florida Panhandle coast, according to the latest ocean current forecast from NOAA's HYCOM model. These winds and currents may be capable of transporting oil east to Panama City, Florida, and oil will continue to threaten the coasts of Louisiana, Alabama, and Mississippi for the remainder of the week as well, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Ocean current forecasts for early next week show a weakening of the eastward-flowing currents along the Florida Panhandle, which would limit the eastward movement of oil so that it would not move past Panama City. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks.

NOAA has launched a great new interactive mapping tool that allows one to overlay wind forecasts, ocean current forecasts, oil location, etc.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA great new interactive mapping tool that allows one to overlay wind forecasts, ocean current forecasts, oil location, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll have an update on Friday.

Jeff Masters

Climate Summaries

Updated: 01:28 PM GMT del 17 Giugno 2010

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Forecast for 92L: dissipation by Friday

By: JeffMasters, 02:17 PM GMT del 16 Giugno 2010

A low pressure system about 700 miles east of the Lesser Antilles Islands, Invest 92L, was near tropical depression status early this morning, but is currently weakening. Infrared satellite loops show the disturbance's heavy thunderstorm activity has decreased markedly in the past few hours, with the cloud top temperatures warming noticeably, indicating that 92L's thunderstorms are no longer pushing as high into the atmosphere. Water vapor satellite loops show that the storm is surrounded on all sides by dry air, though there is a region of moister air in front of it that 92L will encounter on Thursday. Wind shear as diagnosed by the University of Wisconsin is near 20 knots, though the SHIPS model is diagnosing the shear at a higher 25 - 30 knots. This high shear is pushing 92L's heavy thunderstorm activity to the east side of the center of circulation, and the center will probably become exposed to view late this morning. Had 92L been able to maintain the heavy thunderstorm activity it had early this morning for 12 or so hours, it could have been classified as a tropical depression. However, classification as a TD requires persistent heavy thunderstorm activity, typically interpreted to mean 12 hours of consistent heavy thunderstorm activity, and 92L did not meet that criterion.


Figure 1. Morning satellite image of Invest 92L. Image credit: NOAA.

The forecast for 92L: dissipation
Wind shear is the main story in the forecast for 92L, as a band of very high wind shear of 20 - 50 knots lies to the northwest of the storm. The current expected track of 92L carries it into this band of high wind shear, and the SHIPS model (based on the GFS model) is predicting that the shear will remain in the 25 - 30 knot range through Friday. Other models predict higher shear levels. It is likely that the high shear, combined with the dry air surrounding the storm, will destroy 92L by Friday. The National Hurricane Center is giving 92L a low (10% chance) of developing into a tropical depression by Friday morning, and this is a reasonable forecast. It is likely that 92L will bring heavy rain showers and wind gusts up to 35 mph on Friday to the Lesser Antilles Islands. I don't expect 92L to be organized enough to cause flooding problems to any of the islands in its path. None of our reliable global computer models develop 92L into a tropical depression. The rest of the tropical Atlantic is quiet, and none of the reliable computer models is calling for tropical cyclone development in the Atlantic over the next seven days.

Is the formation of 92L a harbinger of an active hurricane season?
According to the Hurricane FAQ, Goldenberg (2000) found that during the period 1944 - 1999, formation of a named storm in the tropical Atlantic south of 22°N and east of 77°W during June and July was a harbinger of at least an average season, and in many cases an above average season. The formation of a storm in this region during June or July is one factor the NOAA and Colorado State University seasonal hurricane forecast teams have used in the past as a predictor for an active season in their early August forecasts. Now, 92L didn't make it to named storm status, though it was pretty close to being a tropical depression. However, the near-formation of 92L into a tropical depression, is, in my mind, a clear harbinger that we can expect a severe hurricane season this year. It's very rare to have a development like 92L in that portion of the tropical Atlantic this early in the season. The lower than average wind shear and higher than average SSTs that helped 92L get organized are more likely than not to carry over into the main portion of hurricane season, giving us a much more active hurricane season than normal.


Figure 2. Synthetic Aperture Radar (SAR) image of the oil spill taken at 7:51 am EDT Tuesday June 15, 2010, by the Canadian Radarsat-1 satellite, operated by MDA GeospatialServices of Richmond, Canada. A large amount of oil was present on the Florida Panhandle coast near Pensacola, and was headed east towards Panama City. Image credit: Center for Southeastern Tropical Advanced Remote Sensing, University of Miami Rosenstiel School of Marine and Atmospheric Science. SAR images have a resolution of 8 - 50 meters, and can be taken through clouds and precipitation.

Oil spill wind and ocean current forecast
Light and variable winds less than 10 knots will blow in the northern Gulf of Mexico for the next five days, according to the latest marine forecast from NOAA. The winds will tend to have a westerly component for the most part, which will maintain a slow (1/4 mph) eastward-moving surface ocean current that will transport oil eastwards along the Florida Panhandle coast, according to the latest ocean current forecast from NOAA's HYCOM model. These winds and currents may be capable of transporting oil east past Panama City, Florida to Cape San Blas by Monday. Oil will continue to threaten the coasts of Louisiana, Alabama, and Mississippi for the remainder of the week as well, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks.

NOAA has lauched a great new interactive mapping tool that allows one to overlay wind forecasts, ocean current forecasts, oil location, etc.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA has lauched a great new interactive mapping tool that allows one to overlay forecasts and oil location observations
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll have an update on Thursday.

Jeff Masters

Hurricane

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Heaviest 1-day rain in Oklahoma City history; 92L fizzles

By: JeffMasters, 02:45 PM GMT del 15 Giugno 2010

Oklahoma City's rainiest day in history brought rampaging floods to the city and surrounding areas yesterday, as widespread rain amounts of 8 - 11 inches deluged the city. Fortunately, no confirmed deaths or injuries have been blamed on the mayhem, though damage is extensive. Oklahoma City's Will Rogers Airport received 7.62" of rain yesterday, smashing the record for the rainiest day in city history. According to the National Climatic Data Center, the city's previous rainiest day occurred September 22, 1970, when 7.53 inches fell. Some rivers continue to rise due to all the rain, and the Canadian River east of downtown Oklahoma City is four feet over flood stage, with major flooding expected today. You can track the flooding using our wundermap with the USGS Flood layer turned on.


Figure 1. Radar-estimated precipitation for the period June 14 - 15, 2010, during the Oklahoma City floods. A large swath of 8 - 10 inches of rain (dark red colors) was indicated, from Oklahoma City northeastwards.

An inordinate number of major U.S. floods this year
We've had an inordinate number of severe floods in the U.S. so far this year. The worst was the May Tennessee flood, which killed 31 people--the highest death toll from a non-tropical cyclone flooding event in the U.S. since 1994, and the most devastating disaster in Tennessee since the Civil War. The Tennessee floods were rated as a 1000-year flood for Middle Tennessee, West Tennessee, South Central and Western Kentucky and northern Mississippi. Two-day rain totals in some areas were greater than 19 inches.Last Friday's disastrous flash flood in Albert Pike Recreation Area, Arkansas, killed twenty people. That flood was triggered by 8+ inches of rain that fell in just a few hours over the rugged mountains west of Hot Springs. And in March, record rains from a slow-moving and extremely wet Nor'easter triggered historic flooding in Rhode Island and Southeastern Massachusetts, with several rivers exceeding their 100-year flood levels. The 16.32" of rain that fell on Providence, Rhode Island, made March that city's wettest month in recorded history.

All of these flooding events were associated with airmasses though brought record-breaking warm temperatures to surrounding regions of the country. For example, during the overnight hours when the June 11 flood in Arkansas occurred, fifty airports in the Southern and Midwestern U.S. had their highest minimum temperatures on record. During the 1000-year flood in Tennessee, 51 warm minimum temperatures records were set in the eastern half of the U.S. on May 1, and 97 records on May 2. Rhode Island's record wettest March also happened to be its record warmest March. And the air mass that spawned yesterday's Oklahoma City floods set record warm minimum temperatures at 22 airports across the central and Eastern portions of the U.S. on Monday. All this is not surprising, since more moisture can evaporate into warmer air, making record-setting rainfall events more likely when record warm temperatures are present. The total number of airports in the U.S. considered for these comparisons is around 500, so we're talking about significant portions of the U.S. being exposed to these record-breaking warm airmasses this year. For the spring months of March - May, it was the 21st warmest such period in the 116-year record, according to the National Climatic Data Center. At the 500 or so largest airports in the U.S., daily high temperature records outnumbered low temperature records by about a factor 2.5, 1200 to 508. Record high minimums this spring outnumbered record low maximums by 1163 to 568. So far in June, record daily highs have outpaced record lows by 176 to 13, and record high minimums have outpaced record low maximums, 419 to 62.

Flooding and global warming
Groisman et al. (2004) found that in the U.S. during the 20th century, there was a 16% increase in cold season (October - April) "heavy" precipitation events (greater than 2 inches in one day), a 25% increase in "very heavy" precipitation events (greater than 4 inches in one day), and a 36% rise in "extreme" precipitation events (those in the 99.9% percentile--1 in 1000 events.) A sharp rise in extreme precipitation is what is predicted by global warming models in the scientific literature Hegerl et al. (2004). According the landmark 2009 U.S. Climate Impact Report from the U.S. Global Change Research Program, "the amount of rain falling in the heaviest downpours has increased approximately 20 percent on average in the past century, and this trend is very likely to continue, with the largest increases in the wettest places." Most of this increase came since 1970, due to the approximate 1°F increase in U.S. average temperature since 1970. That 1°F increase in temperature means that there is 4% more moisture in the atmosphere, on average. According to the 2007 IPCC report, water vapor in the global atmosphere has increased by about 5% over the 20th century, and 4% since 1970. Satellite measurements (Trenberth et al., 2005) have shown a 1.3% per decade increase in water vapor over the global oceans since 1988. Santer et al. (2007) used a climate model to study the relative contribution of natural and human-caused effects on increasing water vapor, and concluded that this increase was "primarily due to human-caused increases in greenhouse gases". This was also the conclusion of Willet et al. (2007).

Dr. Joe Romm over at climateprogress.org has an excellent interview with Dr. Kevin Trenberth of the National Center of Atmospheric Research on the subject of heavy precipitation events and global warming. Dr. Trenberth is the world's leading expert on water vapor in the atmosphere, and he comments that "since the 1970s, on average, there's about a 4% increase in water vapor over the Atlantic Ocean, and when that gets caught into a storm, it invigorates the storm so the storm itself changes, and that can easily double the influence of that water vapor and so you can get up to an 8% increase, straight from the amount of water vapor that's sort of hanging around in the atmosphere. This is reasonably well established." Dr. Trenberth further comments, "Now the physical cause for this is very much related to the water vapor that flows into these storms. And these kinds of storms, well all storms for that matter, reach out on average--this is very much a gross average--about 4 times the radius or 16 times the area of the region that's precipitating, the rain. And for these kinds of storms a lot of the moisture is coming out of the sub-tropical Atlantic and even the tropical Atlantic; some of it comes out of the Gulf of Mexico. And so the moisture actually travels about 2000 miles where it gets caught up in these storms and then it rains down. And the key thing is, that in the tropical and sub-tropical Atlantic the sea temperatures are at very high levels and in fact they're the highest on record at the moment right in the eastern tropical Atlantic. It's going to be interesting to see what that does for this hurricane season coming up."

We cannot say that any of this year's flooding disasters were definitely due to global warming, and part of the reason for this year's numerous U.S. flooding disasters is simply bad luck. However, higher temperatures do cause an increased chance of heavy precipitation events, and it is likely that the flooding in some of this year's U.S. flooding disasters were significantly enhanced by the presence of more water vapor in the air due to global warming. We can expect a large increase in flooding disasters in the U.S. and worldwide if the climate continues to warm as expected.


Figure 2. A portable classroom building from a nearby high school floats past submerged cars on I-24 near Nashville, TN on May 1, 2010. One person died in the flooding in this region of I-24. Roughly 200 - 250 vehicles got submerged on this section of I-24, according to wunderphotographer laughingjester, who was a tow truck operator called in to clear out the stranded vehicles.

Funding issues threaten hundreds of streamgages
According to the USGS web site, river stage data from 292 streamgages has been discontinued recently, or is scheduled for elimination in the near future due to budget cuts. In Tennessee, 16 streamflow gages with records going back up to 85 years will stop collecting data on July 1 because of budget cuts. Five gages in Arkansas are slated for elimination this year. Hardest hit will be Pennsylvania, which will lose 30 of its 258 streamgages. With over 50 people dead from two flooding disasters already this year, now hardly seems to be the time to be skimping on monitoring river flow levels by cutting funding for hundreds of streamgages. These gages are critical for proper issuance of flood warnings to people in harm's way. Furthermore, most of the northern 2/3 of the U.S. can expect a much higher incidence of record flooding in coming decades. This will be driven by two factors: increased urban development causing faster run-off, and an increase in very heavy precipitation events due to global warming.


Figure 3. Streamgages that have been discontinued or are being considered for discontinuation or for conversion from continuous record discharge to stage-only stations. Funds for these 292 threatened streamgages are from the U.S. Geological Survey and other Federal, State, Tribal, and local agencies. For those streamgages that have already been discontinued, extensive efforts were made to find another funding source; however, when no funding was made available the streamgages had to be discontinued. If you have questions about specific streamgages, click on the state of concern on the USGS web page of threatened stream gages.

Dry air disrupting 92L
Invest 92L, which yesterday was a remarkably well-developed African tropical wave for so early in the season, has fizzled, due to dry air. Infrared satellite loops show the disturbance has lost nearly all of its heavy thunderstorms, and water vapor satellite loops show that the storm has wrapped a large amount of dry air to the west into the storm's center of circulation. With the storm continuing to track west-northwest to northwest into dryer air, the prospects for 92L developing into a tropical depression appear dim. With wind shear expected to rise from its current levels of 10 - 15 knots to 20 - 25 knots on Wednesday, the combination of shear and dry air should be able to pretty much destroy 92L on Wednesday. Shear values will likely increase to 30 - 40 knots by Friday, when 92L will move into the northern Lesser Antilles Islands. There is a window of opportunity this afternoon for 92L to fend off the dry air and organize into a tropical depression. One advantage the storm has it that it has developed a well-formed surface circulation. The low-level center of circulation is easy to spot on satellite imagery, since wind shear due to strong upper-level winds from the west have exposed the center to view. The National Hurricane Center is giving 92L a moderate (30% chance) of developing into a tropical depression by Thursday morning. I would put the chances a bit lower, at 20%. Even if 92L does develop into a tropical depression, it is highly unlikely to cause any trouble for the Lesser Antilles Islands, since wind shear and dry air will probably destroy the system before it can reach the islands.


Figure 4. Morning satellite image of Invest 92L. The low-level circulation is easy to spot on satellite imagery, since wind shear due to strong upper-level winds from the west have exposed the center to view. A small clump of heavy thunderstorms is located just east of the exposed center of circulation.

Elsewhere in the tropics
None of the reliable computer models is calling for tropical cyclone development in the Atlantic over the next seven days. There is a small swirl of low clouds visible in satellite imagery at 8N, 22W, just off the coast of Africa, associated with a tropical wave. This circulation is under wind shear of about 20 knots, which is probably too high for such a small circulation to survive in.

Oil spill wind and ocean current forecast
Light, predominantly southwesterly to westerly winds of 5 - 10 knots will blow in the northern Gulf of Mexico most of this week, according to the latest marine forecast from NOAA. The more westerly wind direction is expected to maintain a slow (1/2 mph) eastward-moving surface ocean current that will transport oil eastwards along the Florida Panhandle coast, according to the latest ocean current forecast from NOAA's HYCOM model. These winds and currents may be capable of transporting oil as far east as Panama City, Florida, by the end of the week. Oil will continue to threaten the coasts of Louisiana, Alabama, and Mississippi for the remainder of the week as well, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks.

NOAA has lauched a great new interactive mapping tool that allows one to overlay wind forecasts, ocean current forecasts, oil location, etc.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA has lauched a great new interactive mapping tool that allows one to overlay wi
nd forecasts, ocean current forecasts, oil location, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Why did 92L die so quickly?
2) Is the formation of 92L a harbinger of an active hurricane season?
3) What damage could a hurricane do to oil drilling platforms and underwater pipes at the bottom of the Gulf of Mexico?

Today's show, will be 1/2 hour, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

Climate Change Flood

Updated: 09:59 PM GMT del 16 Agosto 2011

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Unusually well-organized 92L disturbance may become a tropical depression

By: JeffMasters, 02:14 PM GMT del 14 Giugno 2010

Invest 92L, a remarkably well-developed African tropical wave for so early in the season, is midway between Africa and the Lesser Antilles Islands. Infrared satellite loops show a modest area of heavy thunderstorms along the north side of 92L's center of circulation, and the storm's heavy thunderstorms activity appears to be slowly increasing in intensity and areal coverage. Upper-level outflow is apparent to the west and north of 92L, and the outflow has been gradually improving this morning. Visible satellite loops do not show much in the way of low-level spiral bands, and my current take from the satellite imagery is that 92L is slowly organizing, and will not become a tropical depression any earlier than 11pm EDT tonight (Monday.) A 4:27 am EDT pass from the WINDSAT satellite saw a partially closed circulation at the surface (open on the south side), with top surface winds of 25 - 30 mph north of the center.


Figure 1. Morning satellite image of Invest 92L (left side of image) and a vigorous new tropical wave that has moved off the coast of Africa (right side.) None of models develop the new tropical wave, but it bears watching.

Sea surface temperatures
Climatology argues against development of 92L, since only one named storm has ever formed between Africa and the Lesser Antilles Islands in the month of June--Tropical Storm Ana of 1979 (Figure 2). However, sea surface temperatures (SSTs) underneath 92L are an extremely high 28°C, and will increase to 29°C by Thursday. In fact, with summer not even here, and three more months of heating remaining until we reach peak SSTs in the Atlantic, ocean temperatures across the entire Caribbean and waters between Africa and the Lesser Antilles are about the same as they were during the peak week for water temperatures in 2009 (mid-September.)

Dry air not a problem for 92L until Wednesday
The disturbance doesn't have to worry about dry air today or Tuesday--Total Precipitable Water (TPW) loops show a very moist plume of air accompanies 92L, and water vapor satellite loops show that the center of 92L is at least 200 - 300 miles from any substantial areas of dry air. As 92L continues to push northwest, though, the SHIPS model is predicting that relative humidity at middle levels of the atmosphere will fall from the current value of about 70%, to 60% on Wednesday. This dry air may begin to cause problems for 92L on Wednesday, especially since wind shear will be increasing at the same time. Tropical cyclones are more vulnerable to dry air when there is substantial wind shear, since the strong winds causing the shear are able to inject the dry air deep into the core of the storm.

Madden-Julian Oscillation
The 60-day cycle of enhanced thunderstorm activity called the Madden-Julian Oscillation is currently favoring upward motion over eastern tropical Atlantic, and this enhanced upward motion helps create stronger updrafts and higher chances of tropical cyclone development.


Figure 2. Tropical Storm Ana of 1979 was the only June named storm on record to form between Africa and the Lesser Antilles Islands.

Wind shear
A major issue for 92L, like it is for most June disturbances, is wind shear. The subtropical jet stream has a branch flowing through the Caribbean and tropical Atlantic north of 10° N that is bringing 20 - 40 knots of wind shear to the region. Our disturbance was located near 10°N, 40°W at 8am EDT this morning, a few hundred miles south of this band of high shear, and is currently only experiencing 5 - 10 knots of shear. This low amount of shear should allow for some steady development of 92L over the next two days as it tracks west-northwest or northwest at 15 mph. The latest run of the SHIPS model is predicting the shear will rise to 20 knots on Wednesday, which may start to cause problems for 92L.

The forecast for 92L
The National Hurricane Center is giving 92L a high (60% chance) of developing into a tropical depression by Wednesday morning, which is a reasonable forecast. The odds of development have increased since yesterday, as the storm has moved considerably to the northwest, away from the Equator. Now it can leverage the Earth's spin to a much greater degree to help get it get spinning. It is quite unusual for a tropical depression to form south of 8°N latitude.

I expect that 92L's best chance to become a tropical depression will come on Tuesday, and the storm could strengthen enough by Wednesday to be named Tropical Storm Alex. The farther south 92L stays, the better chance it has at survival. With the system's steady west-northwest movement this week, 92L will probably begin encountering hostile wind shear in excess of 20 knots by Wednesday, which should interfere with continued development. Several of our reliable models do develop 92L into a tropical storm with 40 - 55 mph winds, but all of the models foresee weakening by Thursday or Friday as 92L approaches the Lesser Antilles Islands and encounters high shear and dry air. I doubt 92L will be anything stronger than a 45 mph tropical storm when it moves through the northern Lesser Antilles Islands on Friday and Saturday, and it would be no surprise if wind shear has destroyed the storm by then. However, as usual, surprises can happen, and the GFS and the SHIPS model (which is based upon the GFS) do indicate that more modest levels of wind shear in the 15 - 20 mph range late this week may allow 92L to stay stronger than I'm expecting. Residents of the islands--particularly the northern Lesser Antilles--should follow the progress of 92L closely, and anticipate heavy rains and high winds moving through the islands as early as Thursday night.

Oil spill wind forecast
There is little change to the oil spill wind forecast for the coming two weeks. Light winds of 5 - 10 knots mostly out of the south or southeast will blow in the northern Gulf of Mexico all week, according to the latest marine forecast from NOAA. These winds will keep oil near the coast of Louisiana, Alabama, Mississippi, and the extreme western Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks.

Jeff Masters

Hurricane

Updated: 02:51 PM GMT del 18 Agosto 2011

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First tropical depression of the season may form from 92L

By: JeffMasters, 03:38 PM GMT del 13 Giugno 2010

An unusually large and well-developed African tropical wave for so early in the season has developed midway between the coast of Africa and South America. The storm was designated Invest 92L by the National Hurricane Center yesterday, and has a good chance of becoming the first tropical depression of the Atlantic hurricane season. Surface winds measured by the 8:23am EDT pass of the European ASCAT satellite revealed that 92L already has a closed surface circulation, though the circulation is large and elongated. Top winds seen by ASCAT were about 25 mph. METEOSAT visible satellite loops show a large and impressive circulation that is steadily consolidating, with spiral bands building inward towards center, and upper-level outflow beginning to be established to the northwest and north.


Figure 1. Morning satellite image of Invest 92L.

Climatology argues against development of 92L, since only one named storm has ever formed between Africa and the Lesser Antilles Islands in the month of June--Tropical Storm Ana of 1979 (Figure 2). However, sea surface temperatures (SSTs) underneath 92L are an extremely high 28 - 30°C, which is warmer than the temperatures reached during the peak of hurricane season last year, in August - September. In fact, with summer not even here, and three more months of heating remaining until we reach peak SSTs in the Atlantic, ocean temperatures across the entire Caribbean and waters between Africa and the Lesser Antilles are about the same as they were during the peak week for water temperatures in 2009 (mid-September.) While 92L will cross over a 1°C cooler patch of water on Monday, the storm will encounter very warm SSTs of 28-29°C again by Tuesday.

The disturbance doesn't have to worry about dry air--Total Precipitable Water (TPW) loops show a very moist plume of air accompanies 92L, and water vapor satellite loops show that the center of 92L is at least 300 - 400 miles from any substantial areas of dry air. The 60-day cycle of enhanced thunderstorm activity called the Madden-Jullian Oscillation is currently favoring upward motion over eastern tropical Atlantic, and this enhanced upward motion helps create stronger updrafts and higher chances of tropical cyclone development.


Figure 2. Tropical Storm Ana of 1979 was the only June named storm on record to form between Africa and the Lesser Antilles Islands.

The forecast for 92L
A major issue for 92L, like it is for most June disturbances, is wind shear. The subtropical jet stream has a branch flowing through the Caribbean and tropical Atlantic north of 10° N that is bringing 20 - 40 knots of wind shear to the region. Our disturbance is currently located at 7°N, well south of this band of high shear, and is only experiencing 5 - 15 knots of shear. This moderate amount of shear should allow for some steady development of 92L over the next few days as it tracks west-northwest at 10 - 15 mph. The National Hurricane Center is giving 92L a medium (30% chance) of developing into a tropical depression by Tuesday morning. Based on visible satellite imagery over the past few hours, I believe this forecast is not aggressive enough, and that 92L has a 50% chance of developing into a tropical depression by Tuesday morning. Another factor holding 92L back is its proximity to the Equator. I would give 92L higher chances of developing if it were not so close to the Equator. The system is organizing at about 7°N latitude, which is so close to the Equator that it cannot leverage the Earth's spin much to help it get spinning. It is quite unusual for a tropical depression to form south of 8°N latitude.

The farther south 92L stays, the better chance it has at survival. With the system's steady west-northwest movement this week, 92L should begin encountering hostile wind shear in excess of 30 knots by Thursday, which should be able to greatly weaken or entirely destroy the storm before it gets to the Lesser Antilles Islands. However, residents of the islands--particularly the northern Lesser Antilles--should follow the progress of 92L closely, and anticipate heavy rains and high winds moving through the islands by Saturday or Sunday next weekend. The GFDL and HWRF models are predicting that 92L will develop into a moderate strength tropical storm that will then be weakened or destroyed by the end of the week, before it reaches the islands. This looks like a reasonable forecast.


Figure 3. The departure of sea surface temperature (SST) from average for June 10, 2010. Image credit: NOAA/NESDIS.

Oil spill wind forecast
There is little change to the oil spill wind forecast for the coming two weeks. Light winds of 5 - 10 knots mostly out of the south or southeast will blow in the northern Gulf of Mexico all week, according to the latest marine forecast from NOAA. These winds will keep oil near the coast of Louisiana, Alabama, Mississippi, and the extreme western Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks.

Jeff Masters

Hurricane

Updated: 03:40 PM GMT del 13 Giugno 2010

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Floods kill 16 in Arkansas; dozens missing

By: JeffMasters, 04:24 PM GMT del 11 Giugno 2010

Heavy rains in excess of seven inches fell over southwestern Arkansas overnight, triggering flash floods that killed at least sixteen people in Caddo Gap, in the rugged Ouachita Mountains. Forty people are missing, with dozens injured. The closest weather station to the disaster is Mount Ida, which recorded 7.16" of rain over the past 48 hours. The USGS is reporting that the Caddo River in Caddo Gap rose from 8.4 feet at 3am CDT to 25.39 feet in just five hours, reaching the 2nd highest flood height on the river since records began in 1989. The Little Missouri River west of Caddo Gap rose 20 feet overnight, from 3 feet to 23.5 feet. The previous highest flood in the 22-year record at this location was just 14.66 feet, set in 2008. You can look at local rainfall amounts and river flood levels in the region using our wundermap with the "USGS River" layer turned on.

Andy Revkin at the New York Times has a blog worth reading on the disaster.


Figure 1. Radar estimated rainfall for June 9 - 11 over Southwest Arkansas. Rainfall amounts in excess of eight inches are indicated for Caddo Gap, where today's flood disaster occurred.

Oil spill update
Southeast to south winds of 10 - 15 knots will blow today through Saturday, according to the latest marine forecast from NOAA. These winds will keep oil near the shores of Louisiana, Alabama, Mississippi, and the extreme western Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The winds become light an variable Sunday through Tuesday, which will result in little movement of the spill. The long range 8 - 16 day forecast from the GFS model indicates a continued regime of light winds, mostly out of the south or southeast. This wind regime will likely push oil onto sections of the eastern Louisiana coast during the period 1 - 2 weeks from now.


Figure 2. The oil spill as imaged on June 10, 2010, by NASA's Aqua satellite.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
NOAA's fact sheet on Hurricanes and the Oil Spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
Oil trajectory forecasts from NOAA
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
Synthetic Aperture Radar (SAR) imagery from the University of Miami

The tropical Atlantic is quiet right now, with no models predicting tropical cyclone development over the next seven days. I'll have a new post either Saturday or Monday.

Jeff Masters

Flood

Updated: 03:58 PM GMT del 12 Giugno 2010

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TSR predicts very active hurricane season; Atlantic May MDR SSTs warmest on record

By: JeffMasters, 01:51 PM GMT del 10 Giugno 2010

The British private forecasting firm Tropical Storm Risk, Inc. (TSR) has joined the ranks of NOAA and Colorado State University in calling for an exceptionally active 2010 Atlantic hurricane season. The latest TSR forecast issued June 4 calls for 17.7 named storms, 9.5 hurricanes, 4.4 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 181% of average. These numbers are much above the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes, and are an increase from their April forecast of 16.3 named storms, 8.5 hurricanes, and 4 intense hurricanes. The TSR June forecast numbers are the highest they've ever gone for in the eleven years they've been issuing Atlantic hurricane season forecasts. TSR predicts a 85-90% chance that activity will rank in the top 1/3 of years historically, and a 85% chance that U.S. landfalling activity will be above average. TSR rates their skill level as 20-34% higher than a "no-skill" forecast made using climatology, though an independent assessment by the National Hurricane Center (Figure 1) gives them somewhat lower skill numbers.

TSR projects that 5.7 named storms will hit the U.S., with 2.5 of these being hurricanes. The averages from the 1950-2009 climatology are 3.2 named storms and 1.5 hurricanes. They rate their skill at making these June forecasts for U.S. landfalls at 10 - 17% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.8 named storms, 0.8 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for their forecast of an exceptionally active season:

1) Their model predicts that sea surface temperatures will be 0.6°C warmer than average in August and September over the Main Development Region (MDR) for Atlantic hurricanes. This is the area between 10°N and 20°N, between the coast of Africa and Central America (20°W - 80°W). It is called the Main Development Region because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)

2) Their model predicts slower than normal trade winds in August and September over the Main Development Region (MDR). Trade winds are forecast to be 1.2 meters per second (about 2.7 mph) slower than average. This would create more spin for developing storms, and allow the oceans to warm up, due to reduced mixing of cold water from the depths and lower evaporational cooling.


Figure 1. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and tropicalstormrisk.com (TSR) from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

2010 hurricane season forecasts from CSU and NOAA
NOAA's 2010 Atlantic hurricane season forecast, issued May 27, called for 18.5 named storms, 11 hurricanes, 5 major hurricanes, and an ACE index 210% of normal (using the mid-point of their range of numbers.) The 2010 Atlantic hurricane season forecast from Colorado State University (CSU) issued on June 2 called for 18 named storms, 10 hurricanes, and 5 intense hurricanes. So, the consensus forecast from NOAA, CSU, and TSR is 18 named storms, 10 hurricanes, and 5 intense hurricanes. The June forecast numbers from all three groups were the highest they've ever gone for in their history of issuing Atlantic hurricane season forecasts.

May SSTs in the tropical Atlantic set a new record
Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest May on record, according to an analysis of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. SSTs in the Main Development Region (10°N to 20°N and 20°W to 80°W) were a remarkable 1.51°C above average during May. This is the fourth straight record warm month, and the warmest anomaly measured for any month. The previous record warmest anomaly for the Atlantic MDR was 1.46°C, set last month. Third place goes to June 2005 and March 2010, with a 1.26°C anomaly. As I explained in detail in a post on record February SSTs in the Atlantic, the Arctic Oscillation (AO) and its close cousin, the North Atlantic Oscillation (NAO), are largely to blame for the record SSTs, though global warming and Atlantic Multidecadal Oscillation (AMO) also play a role. However, trade winds over the tropical Atlantic have increased to near-normal speeds over the past week, since the Bermuda-Azores High has strengthened to near-normal pressures. The Bermuda-Azores High and its associated trade winds are forecast to increase to above average strength during mid-June, according to the latest runs of the GFS model. This means that Atlantic SST anomalies have probably peaked for the year, and we can anticipate that the June SST anomaly in the MDR will not be as great as the May anomaly--and may even fall below the June record set in 2005.


Figure 2. The departure of sea surface temperature (SST) from average for June 10, 2010. Image credit: NOAA/NESDIS.

Oil spill update
Light southeast or south winds of 5 - 15 knots will blow today through Tuesday, according to the latest marine forecast from NOAA. These winds will keep oil near the beaches of Alabama, Mississippi, and the extreme western Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The latest ocean current forecasts from the NOAA HYCOM model are not predicting eastward-moving ocean currents along the Florida Panhandle coast this week, and it is unlikely that surface oil will affect areas of Florida east of Pensacola. Long range surface wind forecasts from the GFS model for the period 8 - 14 days from now show a southeasterly wind regime, which would prevent any further progress of the oil eastwards along the Florida Panhandle, and would tend to bring significant amounts of oil back to the shores of eastern Louisiana next week. If you spot oil, send in your report to http://www.gulfcoastspill.com/, whose mission is to help the Gulf Coast recovery by creating a daily record of the oil spill.


Figure 3. The oil spill as imaged on June 9, 2010, by NOAA's Terra satellite. The spill appears highly reflective in the sunglint portion of the image.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
NOAA's fact sheet on Hurricanes and the Oil Spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
Oil trajectory forecasts from NOAA
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll have a new post on Friday. The tropical Atlantic is quiet right now, with no models predicting tropical cyclone development over the next seven days.

Jeff Masters

Hurricane

Updated: 01:54 PM GMT del 10 Giugno 2010

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La Niña by July?

By: JeffMasters, 01:42 PM GMT del 08 Giugno 2010

El Niño rapidly dissipated in May, and we are now very close to entering into a La Niña event, according to the latest sea surface temperature (SST) data over the tropical Eastern Pacific. The weekly SST readings in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", fell to 0.4°C below average on June 7, a full 1°C drop in just one and a half months. This puts us very close to the -0.5°C threshold needed to be considered a La Niña event, according to NOAA's latest El Niño Discussion. The Australian Bureau of Meteorology showed conditions in the Niña 3.4 region were not quite that cool--0.2°C below average for the week ending June 6. Nevertheless, the speed of the collapse of El Niño makes it likely that a La Niña event is on its way this summer, and NOAA's Climate Prediction Center has issued a La Niña watch. Ten of the 23 El Niño models (updated as of May 19) are predicting La Niña conditions for hurricane season. However, as NOAA's Climate Prediction Center commented in their June 3 advisory, a number of the more reliable models are now calling for La Niña to develop this summer. They comment, "there is an increasing confidence in these colder model forecasts, which is supported by recent observations that show cooling trends in the Pacific Ocean and signs of coupling with the atmospheric circulation." Historically, about 35 - 40% of El Niño events are followed by a La Niña within the same year.


Figure 1. Atlantic named storm, hurricane, and intense hurricane activity since the active hurricane period we are in began in 1995. Both La Niña and neutral years have shown similar levels of Atlantic hurricane activity, though the figures are somewhat skewed by the record-setting year of 2005. Background photo: Hurricane Dean, taken from the Space Shuttle.

It is interesting to note that the last time we had a strong El Niño event, in 1998, El Niño collapsed dramatically in May, and a strong La Niña event developed by hurricane season. History appears to be repeating itself, and I predict the emergence of La Niña by July. Since La Niña events tend to bring lower amounts of wind shear to the tropical Atlantic, we can expect a much more active Atlantic hurricane season than usual in 2010. Since 2010 is similar to 1998 in the behavior of the El Niño/La Niña cycle, it is possible that this year's hurricane season could resemble the 1998 Atlantic hurricane season. That year had about 40% above-average activity, with 14 named storms, 10 hurricanes, and 3 intense hurricanes. The season was relatively late-starting, with only one named storm occurring before August 20. Once the season got going, six named storms affected the Gulf of Mexico, including two hurricanes, Earl and Georges, that passed directly over the location of the Deepwater Horizon oil spill.


Figure 2. Tracks of all named storms for the 1998 Atlantic hurricane season.


Figure 3. Typical regional weather anomalies observed during June - August when La Niña conditions are present. The Caribbean tends to be cloudier and wetter than average, but there is typically little change to temperature and precipitations patterns over North America. Image credit: NOAA Climate Prediction Center.

Oil spill update
Light east, southeast, or south winds of 5 - 15 knots will blow today through Saturday, according to the latest marine forecast from NOAA. These winds will keep oil near the beaches of Alabama, Mississippi, and the extreme western Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The latest ocean current forecasts from the NOAA HYCOM model are not predicting eastward-moving ocean currents along the Florida Panhandle coast this week, and it is unlikely that surface oil will affect areas of Florida east of Fort Walton Beach. Long range surface wind forecasts from the GFS model for the period 8 - 14 days from now show a southeasterly wind regime, which would prevent any further progress of the oil eastwards along the Florida Panhandle, and would tend to bring significant amounts of oil back to the shores of eastern Louisiana next week. If you spot oil, send in your report to http://www.gulfcoastspill.com/, whose mission is to help the Gulf Coast recovery by creating a daily record of the oil spill.


Figure 4. The oil spill on June 6, 2010 at 8:32pm EDT, as seen by Synthetic Aperture Radar (SAR) imagery from the Italian Cosmo-SkyMed (COnstellation of small Satellites for Mediterranean basin Observation) satellite. A large region of oil was a few miles offshore of Pensacola, Florida. Image credit: University of Miami Center for Southeastern Tropical Advanced Remote Sensing, Rosenstiel School of Marine and Atmospheric Science.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
NOAA's fact sheet on Hurricanes and the Oil Spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
Oil trajectory forecasts from NOAA
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
The tropical Atlantic is quiet right now, with no models predicting tropical cyclone development over the next seven days. I'll talk about all this nothingness on my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on Shaun Tanner's blog. Some topics I'll cover on the show:

1) What's going on in the tropics right now--is this typical?
2) New advancements in hurricane science presented at this month's AMS Conference on Hurricanes and Tropical Meteorology last month

Today's show, which will probably be just 1/2 hour, will be at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast, as last week's show was.

I may take a break from blogging Wednesday, as I've got some catching up to do on other duties.

Jeff Masters

Climate Summaries

Updated: 10:19 PM GMT del 21 Ottobre 2011

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Second deadliest tornado of 2010 kills 5 in Ohio; oil spill update

By: JeffMasters, 02:00 PM GMT del 07 Giugno 2010

The second deadliest tornado of 2010 hit Millbury, Ohio, about 10 miles southeast of Toledo, on Saturday night, killing five. The deaths brought this year's tornado death toll to 23, which is, fortunately, well below the approximately 70 deaths we expect to see by mid-June, based on averages from the past three tornado seasons. The deadliest tornado of 2010 was the EF-4 Yazoo City, Mississippi tornado in April, which killed ten. NOAA's Storm Prediction Center recorded 55 tornado reports on Saturday, plus 104 reports of damaging winds and 16 of large hail. The tornadoes hit Iowa, Illinois, Indiana, Michigan, and Ohio. Ohio's killer tornado was preliminarily rated a high-end EF-3 with 165 mph winds, but has now been upgraded to an EF-4 with 175 mph winds. An EF-3 tornado also hit Indiana near Grissom Air Force Base on Saturday, and two EF-3 tornadoes were reported in Illinois, one near St. Anne, and one in Livingston County. Here in Michigan, I found myself making some very late night calls at 12:30 am on Sunday to warn relatives about the Doppler radar signatures of rotating supercells bearing down on them. Hardest hit was the town of Dundee, south of Ann Arbor. An EF-2 tornado swept through the town, damaging Michigan's most visited tourist attraction, Cabela's sporting goods store on US-23. An EF-1 tornado also damaged a building at the Fermi II Nuclear Power Plant on Lake Erie, forcing an automatic shutdown of the nuclear reactor.


Figure 1. Severe weather reports for Saturday, June 5, 2010. Image credit: NOAA's Storm Prediction Center.

Oil spill update
Light winds of 5 - 10 knots today will turn to southeasterly Tuesday through Wednesday, then southerly on Thursday through Friday, according to the latest marine forecast from NOAA. These winds will keep oil near the beaches of Alabama, Mississippi, and the Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The latest ocean current forecasts from the NOAA HYCOM model show that the ocean currents that have carried oil eastward along the Florida Panhandle coast will weaken this week, making it unlikely that oil will penetrate farther eastwards than Panama City, Florida. Long range surface wind forecasts from the GFS model for the period 8 - 14 days from now show a return to a southeastery wind regime, which would prevent any further progress of the oil eastwards along the Florida Panhandle, and would tend to bring significant amounts of oil back to the shores of eastern Louisiana next week. If you spot oil, send in your report to http://www.gulfcoastspill.com/, whose mission is to help the Gulf Coast recovery by creating a daily record of the oil spill.


Figure 2. The oil spill on June 5, 2010 at 11:49pm EDT, as seen by Sythetic Aperature Radar (SAR) imagery from the European Space Agency's ENVISAT satellite. Image credit: University of Miami Center for Southeastern Tropical Advanced Remote Sensing, Rosenstiel School of Marine and Atmospheric Science.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post Wednesday with answers to some of the common questions I get about the spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
Oil trajectory forecasts from NOAA
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Join the "Hurricane Haven" with Dr. Jeff Masters
I'll have a new post on Tuesday. The tropical Atlantic is quiet right now, with no models predicting tropical cyclone development over the next seven days. Also on Tuesday, I'll be continuing our experiment with my live Internet radio show called "Hurricane Haven." The show will be aired at 4pm EDT on Tuesdays during hurricane season. Listeners will be able to call in and ask questions. Some topics I'll cover on the show:

1) What's going on in the tropics right now
2) New advancements in hurricane science presented at this month's AMS Conference on Hurricanes and Tropical Meteorology last month

Tomorrow's show, which will probably be just 1/2 hour, will be at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast, as last week's show was.

Jeff Masters

Tornado

Updated: 08:34 PM GMT del 24 Ottobre 2011

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Long range oil spill forecast

By: JeffMasters, 03:02 PM GMT del 04 Giugno 2010

Onshore winds out of the south, southwest, or west are expected to blow over the northern Gulf of Mexico over through Tuesday, resulting in a continued threat of landfalling oil to Alabama, Mississippi, and the Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The latest ocean current forecasts from the NOAA HYCOM model show that these winds will generate a 0.5 mph current flowing from west to east along the Florida Panhandle coast Sunday through Tuesday. If this current develops as predicted, it will be capable of bringing light amounts of oil as far east as Panama City, Florida, by Wednesday. Long range surface wind forecasts from the GFS model for the period 8 - 14 days from now predict a return to a southeasterly wind regime, which would bring the oil back over Louisiana by mid-June. If you spot oil, send in your report to http://www.gulfcoastspill.com/, whose mission is to help the Gulf Coast recovery by creating a daily record of the oil spill.

Long range oil spill outlook
The National Center for Atmospheric Research (NCAR) issued a press release yesterday showing 4-month model runs (Figure 1) of where the Deepwater Horizon oil spill might go. The model runs show that given typical ocean currents in the Gulf of Mexico, we can expect the oil to eventually affect most of the Florida Panhandle, Keys, and Florida East Coast, as well as coastal areas of South Carolina and North Carolina. Very little oil makes it to the West Florida "Forbidden Zone", where offshore-moving surface currents dominate. The oil may eventually affect three foreign countries: Mexico along the northern tip of the Yucatan Peninsula, Cuba near Havana, and the Bahamas in the Bimini Islands and along the western side of Grand Bahama Island. Once oil does get into the Loop Current, it will probably reach the coasts of France, Spain, and Portugal in about a year. The oil will be too dilute by then to be noticeable, though.

The present ocean current configuration in the Gulf features a newly formed Loop Current Eddy (dubbed "Franklin"), which will tend to capture the majority of oil that flows southwards from the Deepwater Horizon spill site. A plot of drifting buoys (drifters) launched into the Gulf May 19 - 24 (Figure 2) reveals how this clockwise-rotating eddy has been capturing southward-moving surface water. Eddy Franklin will move slowly west-southwest at 2 - 3 mph in the coming weeks. By August or September, the eddy will have moved far enough west that the Loop Current will be able to push northwards towards the spill location again, increasing the chances of oil getting into the Loop Current and being advected through the Florida Straits and up the U.S. Southeast Coast. Between now and mid-August, I doubt that a significant amount of oil will get into the Loop Current, unless a hurricane or tropical storm goes through the Gulf of Mexico. I put the odds of this happening by mid-August at 50%. The odds of a named storm in the Gulf of Mexico will increase sharply after mid-August, when the peak portion of hurricane season arrives. Past history shows a 95% chance of getting two or more named storms in the Gulf of Mexico during hurricane seasons with above-normal activity.


Figure 1. Animation from the National Center for Atmospheric Research (NCAR) showing one scenario of how oil released at the location of the Deepwater Horizon disaster on April 20 in the Gulf of Mexico may move in the upper 65 feet of the ocean.


Figure 2. During the R/V Bellows 19-24 May 2010 Cruise into the Loop Current, drifters were dropped on the eastern edge of the Loop Current. These drifters have all been caught in Loop Current Eddy "Franklin", and are orbiting the central Gulf of Mexico in clockwise loops. Additional drifters deployed by the Coast Guard over the past few weeks (orange colors) are also shown. The colored balloons show the starting location of the drifters. Image credit: University of South Florida.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
Oil trajectory forecasts from NOAA
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami


Figure 2. Visible satellite image of Tropical Cyclone Phet on Friday, June 4, 2010.

Tropical Cyclone Phet unleashes heavy rains on Oman
Tropical Cyclone Phet hit the northern tip of Oman yesterday as a Category 2 storm, bringing torrential rains and killing at least two people. Masirah, Oman recorded sustained winds of 74 mph yesterday, and Sur, Oman on the northeast coast has received 3.25 inches of rain so far. Phet was the 2nd strongest tropical cyclone ever recorded in the Arabian Sea, when it peaked at Category 4 strength with 145 mph. Only Category 5 Cyclone Gonu of 2007, which devastated Oman, was stronger. Phet has emerged from the coast of Oman this morning, but is likely to weaken over the next day due to increased wind shear. Phet should hit Pakistan as a tropical storm on Saturday, bringing heavy rain and serious flooding.

Next update
I'll probably have one update over the weekend. The tropical Atlantic is quiet right now, with no models predicting tropical cyclone development over the next seven days.

Jeff Masters

Air and Water Pollution

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CSU predicts highly active hurricane season; Cyclone Phet approaching Oman

By: JeffMasters, 02:00 PM GMT del 03 Giugno 2010

A very active Atlantic hurricane season is on tap for 2010, according to the seasonal hurricane forecast issued June 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 18 named storms, 10 hurricanes, and 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 185% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step up from their April forecast, which called for 15 named storms, 8 hurricanes, and 4 intense hurricanes. The new forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (51% chance, 31% chance is average) and the Gulf Coast (50% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 65% (42% is average.) This is the most aggressive early June forecast ever issued by the CSU group; the previous most aggressive such forecasts were for the 2006 and 2007 seasons, when the CSU team predicted 17 named storms, 9 hurricanes, and 5 intense hurricanes. Both of these forecasts did poorly, particularly the 2006 forecast, as only 10 named storms, 5 hurricanes, and 2 intense hurricanes were observed.

The forecasters cited four main reasons for an active season:

1) Weak La Niña conditions should develop by the most active portion of this year's hurricane season (August-October). The expected trend towards weak La Niña conditions should lead to reduced levels of vertical wind shear compared with what was witnessed in 2009.

2) Current SST anomalies are running at near-record warm levels. These very warm waters are associated with dynamic and thermodynamic factors that are very conducive for an active Atlantic hurricane season.

3) A weaker-than-normal Azores High prevailed during April-May. Weaker high pressure typically results in weaker trade winds that are commonly associated with more active hurricane seasons.

4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80-85 percent of normalized hurricane damage.

Analogue years
The CSU team picked four previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: weak El Niño to neutral conditions, well above-average tropical Atlantic SSTs, and above-average far North Atlantic SSTs during April - May. Those four years were 2005, the worst hurricane season of all time; 1969, the 3rd worst hurricane season of all time, featuring Category 5 Hurricane Camille which hit Mississippi; 1966, a relatively average year that featured Category 4 Inez that killed 1,000 people in Haiti; and 1958, a severe season with 5 major hurricanes. The mean activity for these five years was 17 named storms, 10 hurricanes, and 5 intense hurricanes, almost the same as the 2009 CSU forecast.

How accurate are the June forecasts?
The June forecasts by the CSU team over the past 12 years have had a skill 19% - 30% higher than a "no-skill" climatology forecast for number of named storms, number of hurricanes, and the ACE index (Figure 1). This is a decent amount of skill for a seasonal forecast, and these June forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. Unfortunately, the CSU June 1 forecasts do poorly at forecasting the number of major hurricanes (only 3% skill), and major hurricanes are what do 80 - 85% of all hurricane damage (normalized to current population and wealth levels.) This year's June forecast uses the same formula as the past two years, which did quite well predicting the 2008 hurricane season (prediction: 15 named storms, 8 hurricanes, 4 intense hurricanes; observed: 16 named storms, 8 hurricanes, 5 intense hurricanes) and 2009 hurricane season (prediction: 11 named storms, 5 hurricanes, 2 intense hurricanes; observed: 9 named storms, 3 hurricanes, 2 intense hurricanes.) An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.44 to 0.58 for their June forecasts, which is respectable.


Figure 1. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. The British firm Tropical Storm Risk (TSR) will issue their outlook for the 2010 Atlantic hurricane season on June 4. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

NOAA's 2010 hurricane season forecast
NOAA issued their forecast for the upcoming Atlantic hurricane season last week. As I discussed in my post on their forecast, NOAA is calling for very active and possibly hyperactive season. They give an 85% chance of an above-normal season, a 10% chance of a near-normal season, and just a 5% chance of a below-normal season. NOAA predicts a 70% chance that there will be 14 - 23 named storms, 8 - 14 hurricanes, and 3 - 7 major hurricanes, with an Accumulated Cyclone Energy (ACE) in the 155% - 270% of normal range. If we take the midpoint of these numbers, NOAA is calling for 18.5 named storms, 11 hurricanes, 5 major hurricanes, and an ACE index 210% of normal. A season with an ACE index over 175% is considered "hyperactive."


Figure 2. Visible satellite image of Tropical Cyclone Phet on Thursday, June 3, 2010.

Tropical Cyclone Phet the 2nd strongest Arabian Sea storm on record
Record heat over southern Asia in May has helped heat up the Arabian Sea to 2°C above normal, and the exceptionally warm SSTs helped fuel Tropical Cyclone Phet into the second strongest tropical cyclone ever recorded in the Arabian Sea. Phet peaked at Category 4 strength with 145 mph winds yesterday, and has weakened slightly to 135 mph winds this morning. Only Category 5 Cyclone Gonu of 2007, which devastated Oman, was a stronger Arabian Sea cyclone.

Phet is over very warm waters of 30 - 31°C, and is under moderate wind shear of 10 - 20 knots. However, the storm is wrapping in dry air from the Arabian Peninsula, which has caused weakening. Visible satellite imagery from this morning (Figure 2) shows that the heavy thunderstorms on the north side of Phet have been eroded away by dry air. Phet is a small storm, and could fall apart fairly quickly if dry air can penetrate into its core. This should happen later today, since wind shear is on the increase, and the shearing winds should be able to disrupt the circulation enough that dry air can force its way into Phet's eyewall. Phet is fairly small, will miss the most heavily populated areas of Oman, and will likely undergo significant weakening before landfall, so the storm is unlikely to cause the kind of catastrophic flooding that Category 5 Cyclone Gonu of 2007 brought to Oman. Gonu killed 50 people and did $4.2 billion in damage. Phet's heaviest rains will be confined to a relatively sparsely populated region of Oman's coast. Rainfall amounts in excess of 6 inches in 18 hours (Figure 3) can be expected along Oman's coast today, which will likely cause extreme flooding.

After Phet's encounter with Oman, the storm will probably be at tropical storm strength when it makes its second landfall in Pakistan. Heavy rains from Phet will be the major danger for Pakistan, and serious flooding can be expected over southern Pakistan.


Figure 3. Forecast rain amounts for the 18-hour period ending at 2am EDT June 3, 2010. Image credit: NOAA/NESDIS.

Oil spill update
Onshore winds out of the south, southwest, or west are expected to blow over the northern Gulf of Mexico over most of the next week, resulting increased threats of oil to Alabama, Mississippi, and the Florida Panhandle, according to the latest trajectory forecasts from the State of Louisiana. The latest ocean current forecasts from the NOAA HYCOM model show that these winds will generate a 0.5 - 1 mph current flowing from west to east along the Florida Panhandle coast Sunday and Monday. If this current develops as predicted, it will be capable of bringing light amounts of oil as far east as Fort Walton Beach, Florida, by Monday. If you spot oil, send in your report to http://www.gulfcoastspill.com/, whose mission is to help the Gulf Coast recovery by creating a daily record of the oil spill.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post Wednesday with answers to some of the common questions I get about the spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll be back Friday with an analysis of the new TSR hurricane forecast and a new forecast by a promising Florida State University model.

Jeff Masters

Hurricane

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Asia records its hottest temperature in history; Category 4 Phet threatens Oman

By: JeffMasters, 01:47 PM GMT del 02 Giugno 2010

A hellish heat wave hit Pakistan last week, sending the mercury to an astonishing 53.5°C (128.3°F) at the town of MohenjuDaro on Wednesday May 26, reported the Pakistani Meteorological Department. While this temperature reading must be reviewed by the World Meteorological Organization (WMO) for authenticity, not only is the 128.3°F reading the hottest temperature ever recorded in Pakistan, it is the hottest reliably measured temperature ever recorded on the continent of Asia. This information comes to me courtesy of Chris Burt, the author of Extreme Weather, who is probably the world's foremost expert on extreme weather records. In a collaborative effort with weather record researchers Maximiliano Herrera and Howard Rainford, Mr. Burt has painstakingly researched the extreme weather records for every country on Earth. They list the previous reliable record high for Asia as the 52.7°C (127°F) temperature measured on June 12, 1919, in the Sindh province of Pakistan. Temperatures exceed 120°F in this region of Pakistan nearly every year, in the late May/early June time frame before the monsoon arrives. Last week's heat wave killed at least 18 Pakistanis, and temperatures in excess of 50°C (122°F) were recorded at nine Pakistani cities on May 26, including 53°C (127.4°F) at Sibi.

All-time hottest temperature for Southeast Asia this month
Record heat also hit Southeast Asia in May. According to the Myanmar Department of Meteorology and Hydrology, Myanmar (Burma) had its hottest temperature in its recorded history on May 12, when the mercury hit 47°C (116.6°F) in Myinmu. Myanmar's previous hottest temperature was 45.8°C (114.4°F) at Minbu, Magwe division on May 9, 1998. According to Mr. Burt, the 47°C (116.6°F) measured on May 12 this year is the hottest temperature measured in Southeast Asia in recorded history.

Bogus extreme temperature records
I'm pleased to say that Chris Burt will be joining wunderground.com as a featured blogger later this year to discuss his work. He's working on a great new website that features weather records for each country of the world, complete with footnotes on disputed records. For example, many record books list Israel as the site of Asia's all-time maximum temperature. Mr. Burt comments: "54°C (129.2°F) has widely been quoted as the highest temperature ever recorded in Israel (and Asia) but there exist serious issues with this record. The temperature was recorded on a thermograph at Tirat Zvi on 21 June 1942. Examination of a copy of this trace (see Bio-Climatic Atlas of Israel by Dr. D. Ashbel, Central Press, Jerusalem, 1950, p.125, Figure 1) actually shows a maximum temperature of 53°C (127.4°F). No explanation is known for this 1°C discrepancy. In comparison with surrounding stations, it is likely that the actual temperature recorded at Tirat Zvi on this data was probably no higher than 52°C (125.6°F), which would be a record high temperature for Israel. Temperatures have reached or exceeded 50°C (122°F) in Israel only during this one episode in 1942.


Figure 1. Temperature trace from Bio-Climatic Atlas of Israel by Dr. D. Ashbel, Central Press, Jerusalem, 1950, p.125 for Tirat Zvi, Israel, the week of June 21, 1942.


Figure 2. Zoom of temperature trace from Bio-Climatic Atlas of Israel by Dr. D. Ashbel, Central Press, Jerusalem, 1950, p.125, for Tirat Zvi, Israel, the week of June 21, 1942. The temperature clearly only reached 53°C, if one reads the graph properly. Thus the 54°C temperature labeled on the graph is not correct.

Mr. Burt comments in his Extreme Weather book that every temperature record for the planet in excess of 129°F can be disputed. All of these records, except for the 134°F recorded at Greenland Ranch in Death Valley, California, were made by French colonial era instruments which were found to be irregular as far as the exposure of the screens used to house the temperature instruments. In some cases, the temperature instrument was housed closer to the ground than it should have been. Mr. Burt will have an in-depth analysis of the evidence later this summer when he begins blogging for us.


Figure 3. Visible satellite image of Tropical Cyclone Phet on Wednesday, June 2, 2010.

Tropical Cyclone Phet the 2nd strongest Arabian Sea storm on record
The record heat over southern Asia in May has helped heat up the Arabian Sea to 2°C above normal. The exceptionally warm SSTs have helped fuel a rare major hurricane in the Arabian Sea today, as Tropical Cyclone Phet underwent an impressive bout of rapid intensification this morning to become a Category 4 storm with 145 mph winds. Phet is a Thai word pronounced as Pet, meaning "Diamond". Intense hurricanes are rare in the Arabian Sea, due to the basin's small size, the interference of the summer monsoon, and the frequent presence of dry air and dust from the Arabian Peninsula. Phet is now the second strongest tropical cyclone ever recorded in the Arabian Sea, behind Category 5 Cyclone Gonu of 2007, which devastated Oman. Third place is held by the 2001 India Cyclone 01A and Very Severe Cyclonic Storm ARB 01 (02A), which were Category 3 storms with 125 mph winds.

Phet is over some of the warmest ocean waters on the planet, 30 - 31°C (86 - 88°F), and warm waters in excess of 26.5°C (80°F) extend to a depth of at least 50 meters (165 feet), resulting in a Tropical Cyclone Heat Potential high enough to allow Phet to attain Category 5 status. Phet is under moderate wind shear of 10 - 20 knots. The Joint Typhoon Warning Center (JTWC) is forecasting Phet to become a Category 5 storm later today. The storm is moving slowly north-northwest towards Oman, and could ingest dry air from the Arabian Peninsula on Thursday, resulting in weakening. It now appears likely that Phet will make landfall in Oman before recurving to the northeast and hitting Pakistan. The region of Oman likely to get hit is sparsely populated, so wind and storm surge damage will not be the main concerns. Phet will spread heavy rains over the heavily populated northern regions of Oman, which will likely cause extreme flooding. Phet has the potential to be worse for Oman than Tropical Cyclone Gonu, which did $4.2 billion in damage and killed 50 people in June 2007.

Impact on Pakistan
Phet is on track to make landfall in Pakistan or Iran after hitting Oman. Phet will be much weakened by passage over Oman, and may only be a tropical storm after crossing the Gulf of Oman and arriving at the Iran/Pakistan coast. Still, Phet's rains could easily cause destructive floods in Iran and Pakistan.

The strongest tropical cyclone on record to hit Pakistan was Very Severe Cyclonic Storm ARB 01 (02A), which hit near Karachi on May 20, 1999, as a Category 3 storm with 125 mph winds. According to Wikipedia, 02A killed 700 people did $6 million in damage (1999 USD). I've also found references to a December 15, 1965 cyclone that killed 10,000 near Karachi, Pakistan.

Oil spill update
Moderate onshore winds of 10 - 20 knots out of the southeast to southwest are expected to blow over the northern Gulf of Mexico over most of the next week, resulting increased threats of oil to Alabama, Mississippi, and the Florida Panhandle, according to the latest trajectory forecasts from NOAA. These persistent southwesterly winds will likely bring oil as far east as Fort Walton Beach, Florida, by Monday.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post Wednesday with answers to some of the common questions I get about the spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

I'll be back Thursday with more on Phet and an analysis of the new Colorado State University hurricane forecast issued by Phil Klotzbach and Bill Gray issued today.

Jeff Masters

Heat

Updated: 05:12 PM GMT del 02 Giugno 2010

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The hurricane season of 2010 arrives

By: JeffMasters, 02:56 PM GMT del 01 Giugno 2010

The hurricane season of 2010 is upon us. With unprecedented sea surface temperatures in the Atlantic, El Niño gone and possibly transitioning to La Niña, a massive oil slick in the Gulf of Mexico, a million earthquake refugees in Haiti at the mercy of a hurricane strike, and an ever-increasing number of people living on our coasts, the arrival of this year's hurricane season comes with an unusually ominous tone. NOAA is forecasting a very active and possibly hyperactive season, and Dr. Bill Gray has said he expects "a hell of a year." However, our ability to forecast hurricane activity months in advance is limited, and we don't yet know how the large scale weather patterns like the Bermuda High will set up during the peak part of hurricane season. In particular, I very much doubt that we are in for a repeat of the unprecedented violence of the Hurricane Season of 2005, with its 28 named storms, 15 hurricanes, and 7 intense hurricanes. While sea surface temperatures are currently warmer this year than in 2005, that year featured some very unusual atmospheric circulation patterns, with a very strong ridge of high pressure over the eastern U.S., record drought in the Amazon, and very low surface pressures over the Atlantic. A repeat of 2005's weather patterns is unlikely, though I am expecting we will get at least four major hurricanes this year. An average year sees just two major hurricanes.


Figure 1. Tracks of all June tropical storms and hurricanes in the Gulf of Mexico, 1995 - 2009. Allison was a subtropical storm (coded blue). Image credit: NOAA Coastal Services Center.

The latest long-range computer model guidance suggests there's no reason to suspect that the first two weeks of this year's hurricane season will bring any unusual activity. Climatologically, June is typically the quietest month of the Atlantic hurricane season. On average, we see only one named storm every two years in June. Only one major hurricane has made landfall in June--Category 4 Hurricane Audrey of 1957, which struck the Texas/Louisiana border area on June 27 of that year, killing 550. The highest number of named storms for the month is three, which occurred in 1936 and 1968. In the fifteen years since the current active hurricane period began in 1995, there have been eleven June named storms (if we include 2008's Tropical Storm Arthur, which really formed on May 31). Five tropical storms have formed in the first half of June in that 14-year period, giving a historical 36% chance of a first-half-of-June named storm. Five June storms in the past 14 years have passed close enough to the Deepwater Horizon oil spill location to have caused significant transport had there been an oil slick on the surface.

Sea Surface Temperatures
Sea Surface Temperatures (SSTs) are at record high levels over the tropical Atlantic between Africa and Central America this year (Figure 2). As I discussed in my May 15 post, the area between 10°N and 20°N, between the coast of Africa and Central America (20°W - 80°W), is called the Main Development Region (MDR) because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.) SSTs in the Main Development Region (10°N to 20°N and 20°W to 80°W) were an eye-opening 1.46°C above average during April. This is the third straight record warm month, and the warmest anomaly measured for any month--by a remarkable 0.2°C. The previous record warmest anomalies for the Atlantic MDR were set in June 2005 and March 2010, at 1.26°C. The Arctic Oscillation (AO) and its close cousin, the North Atlantic Oscillation (NAO), are largely to blame for the record SSTs. The AO and NAO are climate patterns in the North Atlantic Ocean related to fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores-Bermuda High. If the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), this creates a weak Azores-Bermuda High, which reduces the trade winds circulating around the High. During December - February, we had the most negative AO/NAO since records began in 1950, and this caused trade winds between Africa and the Lesser Antilles Islands in the hurricane Main Development Region to slow to 1 - 2 m/s (2.2 - 4.5 mph) below average. Slower trade winds mean less mixing of the surface waters with cooler waters down deep, plus less evaporational cooling of the surface water. As a result, the ocean heated up significantly, relative to normal, over the winter and Spring.

However, over the past two weeks, the AO/NAO has trended close to average, and trade winds over the tropical Atlantic have increased to near normal speeds as the Bermuda-Azores High has strengthened. SST anomalies have been falling in recent weeks, and will continue to fall in the coming two weeks, based on the latest forecast from the GFS model. While I expect that record SSTs will continue into mid-June, current trends suggest that by July, SST anomalies will be close to what they were in 2005. SST anomalies in the MDR could fall below the record 2005 levels by the peak part of hurricane season, August - October. Even so, SSTs in the Caribbean this year will be plenty warm to cause an abnormal number of major hurricanes. These warm SSTs may also cause extensive damage to the coral reefs, which suffered huge die-offs from the record SSTs of 2005.

Typically, June storms only form over the Gulf of Mexico, Western Caribbean, and Gulf Stream waters just offshore Florida, where water temperatures are warmest. SSTs are 28 - 30°C in these regions, which is about 0.5 - 1.5°C above average for this time of year. June storms typically form when a cold front moves off the U.S. coast and stalls out, with the old frontal boundary serving as a focal point for development of a tropical disturbance. African tropical waves, which serve as the instigators of about 85% of all major hurricanes, are usually too far south in June to trigger tropical storm formation. Every so often, a tropical wave coming off the coast of Africa moves far enough north to act as a seed for a June tropical storm. This was the case for Arthur of 2008 (which also had major help from the spinning remnants of the Eastern Pacific's Tropical Storm Alma). Another way to get Atlantic June storms is for a disturbed weather area in the Eastern Pacific Intertropical Convergence Zone (ITCZ) to push north into the Western Caribbean and spawn a storm there. This was the case for Tropical Storm Alberto of 2006 (which may have also had help from an African wave). SSTs are too cold in June to allow storms to develop between the coast of Africa and the Lesser Antilles Islands--there has only been once such development in the historical record--Ana of 1979.


Figure 2. Sea Surface Temperature (SST) departure from average for May 31, 2010. SSTs averaged more that 1°C above average over the entire tropical Atlantic and Gulf of Mexico. Note the large region of below average SSTs along the Equatorial Pacific off the coast of South America, signaling the possible start of an La Niña episode. Image credit: NOAA/NESDIS.

Wind shear
Wind shear is usually defined as the difference in wind between 200 mb (roughly 40,000 foot altitude) and 850 mb (roughly 5,000 foot altitude). In most circumstances, wind shear above 20 knots will act to inhibit tropical storm formation. Wind shear below 12 knots is very conducive for tropical storm formation. High wind shear acts to tear a storm apart. The jet stream's band of strong high-altitude winds is the main source of wind shear in June over the Atlantic hurricane breeding grounds, since the jet is very active and located quite far south this time of year.

The jet stream over the past few weeks has been locked into a pattern where a southern branch (the subtropical jet stream) brings high wind shear over the Caribbean, and a northern branch (the polar jet stream) brings high wind shear offshore of New England. This leaves a "hole" of low shear between the two branches off the coast of North Carolina, which is where Invest 90L formed.

The jet stream is forecast to maintain this two-branch pattern over the coming ten days (Figure 3.) This means that the waters offshore of North Carolina is the most likely place for a tropical storm to form during this period, though the southwestern Caribbean will at times have shear low enough to allow tropical storm formation. The Gulf of Mexico is forecast to have wind shear too high to support a tropical storm during the first half of June. None of our reliable forecast models call for tropical storm formation over the coming 7 days, though the NOGAPS model indicates the possibility of a tropical disturbance forming off the coast of Nicaragua on Friday.


Figure 3. Wind shear forecast from the 00Z GMT June 1, 2010 run of the GFS model for June 7. Currently, the polar jet stream is bringing high wind shear to the waters offshore New England, and the subtropical jet is bringing high wind shear to the northern Caribbean. This leaves the waters off the coast of North Carolina and southern Caribbean under low shear, making these areas the most favored region for tropical storm formation over the next 7 - 10 days. Wind speeds are given in m/s; multiply by two to get a rough conversion to knots. Thus, the red regions of low shear range from 0 - 16 knots.

Dry air and African dust
It's too early to concern ourselves with dry air and dust coming off the coast of Africa, since these dust outbreaks don't make it all the way to the June tropical cyclone breeding grounds in the Western Caribbean and the Gulf of Mexico. Developing storms do have to contend with dry air from Canada moving off the U.S. coast; this was a key reason why our first "Invest" of the year, 90L off the coast of South Carolina, never became a subtropical storm.

Dust expert Professor Amato Evan of the University of Virginia has posted his forecast for African dust for the 2010 hurricane season. Dr. Evan is predicting that due to plentiful rains during last year's rainy season over the Sahel region of Africa, and near average amounts of African dust observed in May 2010 and during the 2009 hurricane season, we can expect near average or moderately below average levels of dust over the tropical Atlantic during the 2010 hurricane season.

Steering currents
The forecast steering current pattern over the next two weeks is a typical one for June, with an active jet stream bringing many troughs of low pressure off the East Coast of the U.S. These troughs will be frequent enough and strong enough to recurve any tropical storms or hurricanes that might penetrate north of the Caribbean Sea. Steering current patterns are predictable only about 3 - 5 days in the future, although we can make very general forecasts about the pattern as much as two weeks in advance. There is no telling what might happen during the peak months of August, September, and October--we might be in for a repeat of the favorable 2009 steering current pattern that recurved every storm out to sea--or the unfavorable 2008 pattern, that steered Ike and Gustav into the Gulf of Mexico.

Summary
Wind shear over the main breeding grounds for June tropical cyclones, the Gulf of Mexico and Western Caribbean, is expected to be high enough over the next two weeks to give us an average chance of a June named storm. I give a 30% chance of a named storm between now and June 15, and a 60% chance for the entire month of June. There is approximately a 30% chance of a June storm passing close enough to the Deepwater Horizon oil spill to cause significant transport of the oil. See my post, What a hurricane would do the Deepwater Horizon oil spill, for more information on this.

Agatha the 6th deadliest Eastern Pacific storm on record
Central America's Tropical Storm Agatha is now the 6th deadliest Eastern Pacific tropical cyclones on record. Agatha was a tropical storm for just 12 hours, making landfall Saturday on the Pacific coast of Guatemala as a 45 mph tropical storm. However, the storm brought huge amounts of rain--as much as 36 inches--to the high mountains of Guatemala. So far, flooding and landslides have killed at least 123 people in Guatemala, with 59 others missing. The storm also killed 9 in neighboring El Salvador, and 14 in Honduras.


Figure 4. Journey to the center of the Earth: a massive sinkhole 200 feet (60 meters) deep opened up in the capital, Guatemala City, after heavy rains from Tropical Storm Agatha. How are they going to fix this hole? Wow! It doesn't even look real.

Guatemala's worst flooding disaster in recent history was due to Hurricane Stan of 2005, which killed 1,513. The deadliest Eastern Pacific tropical cyclone on record for Guatemala was Hurricane Paul of 1982, which made landfall in Guatemala as a tropical depression. Flooding from Paul's rains killed 620 people in Guatemala.

Oil spill update
Light onshore winds out of the south to southwest are expected to blow over the northern Gulf of Mexico all week, resulting increased threats of oil to the Alabama and Mississippi barrier islands, according to the latest trajectory forecasts from NOAA. These persistent southwesterly winds will likely bring oil very close to the Florida Panhandle by Saturday.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post Wednesday with answers to some of the common questions I get about the spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
Gulf Oil Blog from the UGA Department of Marine Sciences
NOAA trajectory forecasts
Deepwater Horizon Unified Command web site
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Surface current forecasts from NOAA's HYCOM model
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Join the "Hurricane Haven" with Dr. Jeff Masters: a new Internet radio show
Today, I'll be experimenting with a live 1-hour Internet radio show called "Hurricane Haven." The show will be aired at 4pm EDT on Tuesdays during hurricane season. Listeners will be able to call in and ask questions. Some topics I'll cover on the first show:

1) What's going on in the tropics right now
2) Preview of the coming hurricane season
3) How a hurricane might affect the oil spill
4) How the oil spill might affect a hurricane
5) New advancements in hurricane science presented at this month's AMS Conference on Hurricanes and Tropical Meteorology
6) Haiti's vulnerability to a hurricane this season

I hope you can tune in to the broadcast, which will be at http://www.wunderground.com/wxradio/wubroadcast.h tml. If not, the show will be recorded and stored as a podcast.

Portlight receives a major grant to fund U.S. disaster relief work
The Christopher and Dana Reeve Foundation has announced today that it is awarding a Quality of Life Grant in the amount of $21,500 to Portlight Strategies, Inc. The grant will fund a ready-to-deploy container specifically outfitted to serve the immediate needs of people with disabilities in the aftermath of hurricanes and other domestic natural disasters. To read more about this award, check out the Portlight blog. Congratulations, Portlight team!

Portlight continues its Haiti response
Ready or not, the rainy season is here for Haiti. Portlight has done a tremendous amount to help the Haitians get ready for the upcoming hurricane season, as detailed in the Haitian Relief Recap blog post made last week. Please visit the Portlight.org web site or the Portlight blog to learn more and to donate to Portlight's efforts in Haiti.


Figure 5. A portion of the 30,000 pounds of rice donated to Haitian earthquake victims by Portlight earlier this month, shipped via the schooner Halie and Mathew.

I'll be back Wednesday afternoon with an analysis of the new Colorado State University hurricane forecast issued by Phil Klotzbach and Bill Gray, due out on June 2.

Jeff Masters

Hurricane

Updated: 10:35 PM GMT del 03 Gennaio 2012

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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