Little change to 90L; flow of oil southwards towards Loop Current shuts off
An extratropical low pressure system a few hundred miles northeast of the Bahamas (90L), has changed little over the past day. (For those of you who were wondering, a discussion of what an "Invest" is can be found in the Tropical Cyclone FAQ). This low has the potential to develop into the season's first depression or subtropical storm, and could be a threat to the Southeast U.S. coast by Tuesday or Wednesday. The SHIPS model predicts that shear will be in the high 30 - 40 knot range through Tuesday, though. The high shear combined with the large amount of dry air to 90L's west seen on water vapor satellite loops will greatly hamper transition of this system to a subtropical storm. This system is expected to move slowly north and then northwestward towards the Southeast U.S. coast over the next three days, and could bring 20 - 30 mph winds and heavy rain to the coast of North Carolina by Tuesday night. Most of the models indicate that Wednesday will be when 90L gets closest to the coast, with a position just off the North or South Carolina coast. All of the major models currently indicate that 90L will not make landfall, but will move slowly northeastward out to sea late next week as a trough of low pressure moving across the Eastern U.S. picks up the storm. While the storm will initially form in a region of high wind shear and be entirely extratropical, it will move into a region of lower wind shear in a gap between the polar jet stream to the north and the subtropical jet stream to its south by Wednesday. At that time, the low will be positioned near the warm waters of the Gulf Stream, and will have the opportunity to develop a shallow warm core and transition to a subtropical storm. The counter-clockwise flow of air around this low will probably lead to offshore winds over the oil spill region Tuesday through Wednesday, keeping oil away from the coasts of Alabama and the Florida Panhandle, but pushing oil southwards towards the Loop Current. Wunderbloggers Weather456 and StormW have more detailed discussions of the potential development of 90L.
Figure 1. Visible satellite image of 90L this afternoon.
Heavy rainfall threat for Haiti diminishes
Moisture is expected to increase across most of the Caribbean next week, leading to seasonally heavy rains across much of the region. A concentrated tropical disturbance capable of bringing dangerous flooding rains to Haiti is no longer being indicated, but the normal heavy rains that we can expect this time of year will likely begin affecting the island over the next several weeks.
Flow of oil southward towards the Loop Current shuts off
Light southeast to east winds are expected to blow over the northern Gulf of Mexico today through Monday, resulting in potential oiling of Louisiana shorelines from the mouth of the Mississippi River westward 150 miles, according to the latest trajectory forecasts from NOAA. These winds shut off the flow of oil southwards towards the Loop Current, as seen in the latest SAR satellite imagery (Figure 2). However, winds will shift to offshore out of the north or northeast Tuesday and Wednesday, due to counter-clockwise flow of air around the approaching 90L storm. This wind direction change should give some relief to the hard-hit Louisiana coast. If 90L becomes strong and lingers off the Southeast U.S. coast for several days, a significant amount of oil could get pumped into the Loop Current late next week.
Figure 2. Synthetic Aperture Radar (SAR) image of the oil spill taken at 8:53am EDT May 22, 2010, by the Canadian Radarsat-1 satellite, operated by MDA GeospatialServices of Richmond, Canada. The plume of oil being drawn south towards the Loop Current has been cut off. 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 threat to the Keys uncertain
Satellite imagery from today's pass of NASA's Terra satellite and the European Envisat satellite were inconclusive as to the presence of oil in the Loop Current. It is likely that the oil has dispersed significantly over the 500-mile course it has taken from the site of the Deepwater Horizon blowout. I expect some oil is close to completing the full loop of the Loop Current and is now headed east towards the Keys, as depicted in the "Uncertainty" area in the latest NOAA 72-hour offshore trajectory forecast. If this estimate is correct, the Keys could see oil as early as Wednesday. However, this is not a sure thing. As I discussed in my post Wednesday, the Loop Current is very unstable right now, and is ready to cut off into a giant clockwise-rotating eddy, an event that occurs every 6 - 11 months. This event could occur today or tomorrow, in which case the ribbon of southwestward-moving oil would turn due west and then north, eventually winding up back near the site of the Deepwater Horizon blowout. Roffer's Ocean Fishing Forecast Service has a nice discussion on the possibility of the Loop Current cutting off into a Loop Current Eddy, and they note in today's discussion that there appears to be a developing eastward flow of water directly from the Yucatan Peninsula to the Florida Keys. Keep in mind, though, that during the first month that a Loop Current Eddy forms, it exchanges a considerable amount of water with the Loop Current. Even if a Loop Current Eddy forms today, I still expect we will see some oil make the turn eastward and flow past the Florida Keys by Wednesday. My guess is that the oil will be too thin and scattered to cause significant problems in the Keys, but there is great uncertainty on this.
Oil spill resources
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
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
I'll be back with a new post Monday morning.
Jeff Masters
Reader Comments
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Not sure, but if that is the case, I can see why.
Yes, they NHC would do an update if warrented. They obviously don't see the need to do so yet.
Morning
LINK
If this thing was over land I would think it is a mid lat cyclone haha. You could see a weak trailing front with a nice ridge to the NE and where a warm front would be, it would link up perfect with the stationary boundary draped over the Atlantic. yes yes i know there is no seperation of air mass and there is no front there.
The NHC names subtropical storms. And by the looks of it....it better start filling as you said cuz it got 4 days ahead of it. Most models deepen this system.
thats a lot of dry air!!
That is funny.
Atlantic version of Barry? It too, developed in 40 knot shear.
Morning 456, Ha, Reed, everyone else!
Yea I am going against the grain. While I know you only need 23C SSTs to create a subtrop system but it hs a fight on its hands with the dry air and shear. Granted the shear is to the east but the center is not really producing a ton of convection to really get warming of the core going. It could get close just dont think it is going to make it.
- Felix
- Humberto
- Luis
- Marylin
True! In Tampa's post it looks more like something that should be trucking across the great plains...
really hard to tell.. need to wait for more sat pics.
It will be.
Information About Low (Invest 90L)
Storm information valid as of: Sunday, May 23, 2010 12:00 Z
Coordinates: 24.5N 70.0W
Location: 462 miles (744 km) to the E (95°) from Nassau, Bahamas
Pressure (MSLP): 1007 mb (29.74 inHg | 1007 hPa)
Sustained wind speed (1 min. avg.): 25 knots (29 mph | 13 m/s)
*90L continues to strengthen, NHC saying, " THIS LOW IS FORECAST TO CONTINUE TO DEEPEN OVER THE
NEXT 48 HOURS AND IS EXPECTED TO BE A GALE IN A FEW HOURS AT
1200 UTC."
its def. not drifitng West.
AOI
AOI
AOI
AOI
You don't get out much. Times haven't changed that much.
Not very organized at all......Shear is ripping 90L...conditions might improve some. Its a wait and see!
Well actually the entire broad center thanks to jumps north of west and south of west averaged out has been drifting west since last night.
Reliable enough to use them as a guidance. They are doing pretty good so far despite multiple center relocations.
Maybe. But he was talking about on the satellite picture and was referring to the present. So no it is not drifting "westward" as he put it rather it is drifting northward.
Credit: AP
Workers, bottom right, stand by to clean oil that encroaches on a boom and a land bridge which was built by the Louisiana National Guard to hold back oil from the Deepwater Horizon oil spill in Grand Isle, La., Friday, May 21, 2010. (AP Photo/Gerald Herbert)
by WWLTV.com
Posted on May 22, 2010 at 6:47 PM
GRAND ISLE, La. - Jefferson Parish Emergency managers say they have commandeered all of BP's hired boats in Grand Isle.
A representative for Jefferson Parish Emergency chief Deano Bonano said they requested immediate action after oil moved into the marsh passes and onto the beaches in Grand Isle.
He said more than 40 boats were sitting idle while he watched the oil rush into the passes.
At around 5:30 p.m., Jefferson Councilman Chris Roberts confirmed the boats have been commandeered by JP emergency managers.
I thought so.
Looks more organized to me. In fact it looks the best it has yet
Well the old center is drifting south west. The little spin he pointed out is drifting west and the area of convection (possibly another swirl underneath) is drifting nw. So still averaged out its drifting mostly west. Probably more like west north west but its just meandering so it really doesnt matter right now.
Apparently you forgot this one...
Look at the amount of dry air with Andrea
maybe not for a tropical system. But this system is currently non-tropical.
Oil Threatens Pelicans
Added by The Times-Picayune on May 22, 2010 at 6:55 PM
An island that is home to hundreds of brown pelican nests as well at terns, gulls and roseated spoonbills is impacted by oil, seen on the grass at the water line, from the Deepwater Horizon Oil Spill just inside the the coast of Louisiana, Saturday, May 22, 2010. (AP Photo/Gerald Herbert)
But won't that hamper its development???
Thanks for the image. That is pretty interesting. The moisture does at some point start to wrap around the center though. i guess that is what we are waiting to see here. It could happen.
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN MAY 23 2010
TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.
BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC...
...SPECIAL FEATURES...
AS OF 23/0900 UTC...A SURFACE TROUGH EXTENDS FROM 30N68W TO AN
EMBEDDED 1007 MB LOW AT 25N70W TO HISPANIOLA AT 20N71W.
SCATTERED MODERATE CONVECTION IS E OF THE TROUGH AXIS FROM
25N-29N BETWEEN 66W-69W. SCATTERED SHOWERS ARE ALSO OVER
HISPANIOLA. THIS LOW IS FORECAST TO CONTINUE TO DEEPEN OVER THE
NEXT 48 HOURS AND IS EXPECTED TO BE A GALE IN A FEW HOURS AT
1200 UTC. THE PRESSURE GRADIENT IS ESPECIALLY TIGHT N OF THE LOW
CENTER AND CONVECTION IS NOT IMMEDIATELY AROUND THE CENTER THUS
THE SYSTEM DOES NOT APPEAR TO BE VERY TROPICAL IN NATURE. THE
AREA OF GALE FORCE WINDS WILL DRIFT N FOR THE FIRST 24 HOURS
THEN DRIFT NW. IN ADDITION...A SMALL UPPER LEVEL LOW IS
PRESENTLY CENTERED NEARBY AT 26N68W PROVIDING DIFFLUENCE E OF
THE UPPER CENTER TO 55W.
you are referring to the other centers. There is only one center right now and it IS moving North. The offical track and position agree with me
Wind: 30 MPH — Location: 24.5 70.0W — Movement: NNW
I rather agree with the offcial and my own knowledge.
Pass da syrup please..
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