Bill intensifies to Category 4; globe has 5th warmest July on record
Category 4 Hurricane Bill is now the the fourth strongest tropical cyclone to appear on the planet so far this year, and may grow even stronger. Visible and infrared satellite imagery continue to show an impressive, well-organized, hurricane, with plenty of low-level spiral banding and upper-level outflow well-established on all sides except the west. On Bill's west side, upper-level winds from the west are creating a modest 10 knots of wind shear, which is giving the hurricane a bit of a squashed appearance there.
Wind shear is forecast to remain low to moderate, 5-15 knots, for the next four days. Sea Surface Temperatures (SSTs) will rise steadily from 28.5°C today to 29°C on Friday. Total ocean heat content is at a maximum today, and will gradually decline over the next four days. Bill should be able to take advantage of these favorable conditions a remain a major hurricane the next three days.
Figure 1. Visible satellite image from NASA's Aqua spacecraft at 12:40pm EDT Tuesday August 18, 2009. Image credit: NASA GSFC.
Water vapor satellite loops show a small "short-wave" trough of low pressure to the north-northwest of Bill, and this trough has turned Bill on a more northwesterly track over the past two days. Bill will miss the Lesser Antilles Islands, and the main impact of the hurricane on these islands will be high waves. The short wave trough (so called because it has a relatively small amplitude and wavelength) is not strong enough to turn Bill due north, and Bill is also expected to miss Bermuda. High waves and sustained winds of 20 - 30 mph are the worst that Bermuda is likely to get from Bill.
Figure 2. Visible satellite image of Bill's eye zoomed in, taken from NASA's Aqua spacecraft at 12:40pm EDT Tuesday August 18, 2009. Image credit: NASA GSFC.
An unusually strong "long wave" trough of low pressure (called long wave because of its large amplitude and wavelength) is expected to develop along the U.S. East Coast late this week. This trough will turn Bill to the north, and also bring high levels of wind shear in the 40 - 65 knot range on Sunday. Exactly where this turn occurs is still not clear. The models continue to be in two camps: an eastern camp (GFS, GFDL, HWRF, and ECMWF) that takes Bill 300 - 500 miles east of Cape Cod, and a more western camp (NOGAPS, UKMET) that bring Bill within 150 - 200 miles of Cape Cod. Both sets of models bring Bill ashore over the Canadian provinces of Newfoundland or Nova Scotia. Bill will be weakening rapidly as it makes landfall, and is likely to be a Category 1 hurricane if it hits Nova Scotia, or strong tropical storm if it hits Newfoundland.
Bill's big waves
Large swells from Bill will begin impacting the U.S. East coast from Florida to Maine beginning Friday night or Saturday morning. Seas will build to 5 - 10 feet in the offshore waters from central Florida northwards to South Carolina, and to 10 - 15 feet from North Carolina to Cape Cod. Near shore, waves will be about 40% less. This will cause a significant coastal erosion event along some portions of the coast. The latest run of the NOAA Wavewatch III model suggests that significant wave heights near Bill's center will reach 50 feet on Sunday. Since maximum wave height is typically about a factor of 1.9 greater than the significant wave height (which is the average trough-to-crest height of the top 1/3 largest waves), a few huge waves near Bill's center may reach 95 feet high.
Possible impacts to New England
The current set of computer model runs predicts that the center of Bill will pass Cape Cod, Massachusetts Sunday afternoon or evening. Tropical storm-force sustained winds of 39 mph or greater currently extend out 185 miles to the west of Bill's center, so that if Bill maintains its current wind distribution, Cape Cod could see sustained winds of about 40 mph Sunday night if the models predicting a more westerly path are correct. However, Bill will not keep this same radius of winds. The hurricane will weaken considerably beginning Sunday morning, once the storm gets caught up in the approaching long wave trough. High wind shear of 40 - 65 knots due to strong southwesterly winds aloft will act to compress the hurricane in the east-west direction, keeping the hurricane's strongest winds away from Cape Cod. The highest winds are likely to be no more than 30 mph on Cape Cod from Bill, if the storm follows the track of the western camp of models nearest to the Massachusetts. A few rain squalls may affect coastal Massachusetts, but the main impact of Bill on New England is likely to be coastal erosion from high waves.
Elsewhere in the tropics
The remains of Tropical Storm Ana are bringing scattered heavy rain showers to the Bahamas and Florida today. The remains are disorganized, and are not likely to re-develop. The only model calling for a new tropical cyclone to develop in the Atlantic over the next seven days is the GFS model, which predicts development off the coast of Africa about 7 days from now.
Fifth warmest July on record globally; a cold July in the U.S.
The globe recorded its fifth warmest July since record keeping began in 1880, according to NOAA's National Climatic Data Center. NOAA rated the period January - July 2009 as the sixth warmest such period on record. NASA's Goddard Institute for Space Studies rated July 2009 as the 2nd warmest July on record, behind July of 1998. For the second month in a row, global ocean Sea Surface Temperatures (SSTs) in July were the warmest on record, 0.59°C (1.06°F) above the 20th century average. This broke the previous July record set in 1998. The record July SSTs were due in part to an ongoing El Niño event in the Eastern Pacific, which has substantially warmed a large stretch of the tropical Eastern Pacific Ocean. As El Niño conditions mature during the coming months, near-record global ocean and land temperatures will probably continue. Now that El Niño conditions have been well-established for three months, the atmosphere has begun to heat up in response. It typically takes up to seven months for the atmosphere to heat up in response to ocean heating from an El Niño. This may explain why June of 2009, which independent assessments by NOAA, NASA, and the UK Hadley center agreed was the 2nd or 3rd warmest June on record at the surface, recorded only average satellite-measured temperatures in the lower atmosphere. In contrast, the July satellite-measured temperatures in the lower atmosphere were the 2nd or 3rd warmest on record, in agreement with the assessments that surface temperatures were the 2nd to 5th warmest on record.
Figure 3. Departure of temperature from average for July 2009. Image credit: NOAA/NCDC.
A cold July for the U.S.
For the contiguous U.S., the average July temperature of 23.1°C (73.5°F) was the coolest since 1994, and July temperatures were the 27th coolest in the 115-year record, according to the National Climatic Data Center. Ohio, Illinois, Indiana, Pennsylvania, Iowa, and West Virginia experienced their coolest ever July. Kentucky, Missouri, Michigan, and Wisconsin recorded their second coolest July in history. A strong trough of low pressure parked itself over the eastern portion of the U.S. in July, funneling down plenty of cold air from Canada. In the western U.S., a ridge of high pressure dominated, bringing unusually hot conditions. Arizona recorded its 3rd warmest July on record, and Seattle, Washington recorded its hottest day in history on July 28, notching a 103°F reading. This was 3°F above the previous record set in 1994.
U.S. precipitation was near average in July, with the month ranking 40th wettest in the 115-year record. U.S. tornado activity was above average in July, according to NOAA's Storm Prediction Center. However, no tornado deaths occurred in July.
At the end of July, 14% of the contiguous United States was in moderate-to-exceptional drought. This is a drop from the 19% figure observed at the beginning of the year. These extreme drought regions were exclusively in South and Central Texas.
I'll have an update Thursday morning.
Jeff Masters
Reader Comments
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Think it starts on the 0345UTC frame and ends at 0615UTC.
1. Anybody else notice how clearly that offshore trough is showing up in the WV? Very cool.
2. Anybody else realize how far WEST Bill has to go to line up with the NHC track? The Wward jogs are not actually out of line with expectation. I'm not going to get "parrie" abt Wward motion unless it suddenly brings Bill well west of 65W before it crosses 25N. Anything else is business as usual.
I can't recall them ever mentioning anything in any discussion about a USA hit. Not saying they've excluded the USA, just can't recall them mentioning them......yet.
They seem pretty sure on track.
True about it being south of a NW track the entire time. I think he's on a 305 track now.
getting to close to bhamas now could he be taking the southern route of the nhc cone instead oihh lets hope he dosent ride that line
Daily Weather BlogLast Updated on 08/19/2009 at 11:08pmBy Pete BouchardWell it's official. Despite being tickled by a sea breeze in the early afternoon, we made a mid-afternoon run for 90 and made it.
Heat wave status in Boston!
Already the temperatures are falling and the cooler air is coming in. This will last for a whole day before the muggy air comes roaring back on Friday.
Good news? Thunder is only "chancy" through Saturday. Bad news? It's all because the fronts and weather systems are waiting for Hurricane Bill to make his move. We don't need them to stop, we need them to move...Bill...outta here!
See this?
That's what is known as "the benchmark" in weather. If Bill goes to the left of that mark, he may hit hit us. If he goes to the right, we're just watching the surf and talking about what "mighta been".
It's as simple as that. Right now, the weather maps are sending him several hundred miles offshore. But there are a couple of outliers that send him right off of Chatham and Nantucket - and they weren't showing that scenario this morning or last night. If he doesn't make that last minute turn to the right Saturday night, he could sail right onto Cape Cod.
On this, the anniversary of Hurricane Bob (1991), we're on pins and needles.
(And as a matter of record, when the name Bob was retired in 1992, he was replaced with Bill.)
Surf's up!
Pete
LOL...I was just thinking about that when I saw your avatar. Anxiously awaiting your new one....
Robert Herbert stressed the point that not every hurricane that went through his hypothetical boxes hit Florida. Nevertheless he stressed that every storm that went through either box should be monitored closely.
Please out there, be my guest in correcting me if I'm wrong.
Evening all. This shows the trough that Hunker is talking about thats supposed to turn Bill to the north. Hope it helps. :)
Link
LOL.
It looks like last night was the peak for Bill.
Shear should increase over the next 24 hours.
The official GFS track is almost an outlier to the EAST of all of its own ensemble tracks. That doesn't make sense. If the official track was the average of all the ensembles, the GFS track would be about 5 degrees West of current track when it crosses 40N.
What gives?
Location: 20.7°N 58.9°W
Max sustained: 135 mph
Moving: NW at 17 mph
Min pressure: 945 mb
I see Bill slowed down...that is good right? And still moving NW.
Maybe it would be an eye opener to some.
I doubt it would be a problem using it.
Actually it's peak is right now if anything, has the lowest pressure so far.
03 GMT 08/19/09 17.2N 53.4W 125 952 Category 3 Hurricane
09 GMT 08/19/09 18.0N 54.9W 135 948 Category 4 Hurricane
15 GMT 08/19/09 18.7N 56.3W 135 950 Category 4 Hurricane
21 GMT 08/19/09 19.8N 57.6W 135 947 Category 4 Hurricane
03 GMT 08/20/09 20.7N 58.9W 135 945 Category 4 Hurricane
Based on pressure...sure.
But ADT has shown a gradual weakening phase.
Hear we may have an AOI in the GOM next week. You hearing this? What is your thought on that?
Don't let Bill stress u out....
Also note that it is an unusually strong trough for this time of year across the plains/midwest. Te NHC has a good handle on Bill.
Yep the GFS is showing that!
Yeah, I saw that. I wonder where it would go...hmmmm
CONUS landfall threat continues to wane. Less spectators.
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