Bonnie weakens to a tropical depression
Tropical Depression Bonnie is nearing the end of its traverse of South Florida, and passage over land has significantly disrupted the small storm. Satellite images show almost no heavy thunderstorms near Bonnie's center of circulation, and the center is now exposed to view. Radar-estimated rainfall from the Key West radar shows that Bonnie dumped very little rain on South Florida--maximum rainfall amounts from the storm were about four inches over a small region southwest of Miami. Water vapor satellite loops show that Bonnie is embedded in a large area of dry air, thanks to an upper level low to the west over the Gulf of Mexico. This low has brought an increasing amount of wind shear to Bonnie today, and shear has increased from 20 knots this morning to 25 knots this afternoon. Surface observations in South Florida currently don't show any tropical storm force winds. Bonnie's top winds today were at Fowey Rocks, which had sustained winds of 46 mph, gusting to 53 mph, at 10:45 am EDT.
Figure 1. Satellite image of Bonnie from NASA's MODIS instrument, taken at 17:10 UTC July 23, 2010. Image credit: NASA/.
Track Forecast for Bonnie
The latest set of model runs from 8am EDT (12Z) are very similar to the three previous sets of runs, and this degree of consistency gives me confidence that Bonnie will stay within the cone of uncertainty depicted on the track forecast images. The projected track will take Bonnie over the oil spill region, and the storm's strong east to southeasterly winds will begin to affect the oil slick on Saturday morning. Assuming Bonnie doesn't dissipate over the next day, the storm's winds, coupled with a likely storm surge of 2 - 4 feet, will drive oil into a substantial area of the Louisiana marshlands. However, the current NHC forecast has Bonnie making landfall in Louisiana near 9pm CDT Saturday night. According to the latest tide information, this will be near the time of low tide. This will result in much less oil entering the Louisiana marshlands than occurred during Hurricane Alex in June. That storm brought a storm surge of 2 - 4 feet and sustained winds of 20 - 30 mph that lasted for several days, including several high tide cycles. The latest oil trajectory forecasts from NOAA (Figure 2) predicts potential oil impacts along a 150-mile stretch of Louisiana coast on Sunday.
Figure 2. Oil Trajectory forecast for Sunday for the Deepwater Horizon oil spill. Image credit: NOAA.
Intensity Forecast for Bonnie
Bonnie has been disrupted by its passage over land, and it will take at least six hours for the storm to reorganize once it moves over the warm waters of the Gulf of Mexico tonight. This process will be hindered by the large upper-level low to its west. If the low remains in its present location, relative to Bonnie, it will bring high wind shear of about 20 - 30 knots to the storm. This will allow for only slow intensification, or may even destroy Bonnie. Bonnie is unlikely to intensify to more than a 50 mph tropical storm, and I give a 30% chance it will dissipate over the Gulf of Mexico before making landfall. The GFDL model predicts Bonnie could hit the Gulf Coast as a 50 mph tropical storm, but the other major models such as the HWRF, GFS, ECMWF, and NOGAPS show a much weaker storm. I don't give Bonnie any chance of becoming a hurricane. NHC is putting the odds of Bonnie being a hurricane at 2 pm Saturday at 4% (5pm advisory.)
If you are wondering about the specific probabilities of receiving tropical storm force winds at your location, I recommend the wind probability product from NHC. The latest probabilities of various locations getting tropical storm force winds, 39 mph or higher, from the 5pm EDT advisory:
Buras, LA 30%
New Orleans 28%
Mobile, AL 37%
Pensacola, FL 30%
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 update
I'll have an update Saturday morning.
Jeff Masters
Reader Comments
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I've seen that exact statement about 1,000 times this season.
LMAO...Mike Seidel....no wind at Dauphin Island,AL.!!!!!!!!! Sea oats dead still.
She looks to be popping up again, a little, lol.
Persistent...
I agree.
Hope is not an effective plan.
(Straightline^projection using its last 2 positions. Take with HUGE grain of salt)
Copy&paste 26.4N83.4W, 26.7N84.4W, 27.0N85.1W-27.6N86.1W, 27.6N86.1W-29.7N89.7W, BIX, 22.3N74.0W, 18.5N87W, TAM, 28.7N88.4W into the GreatCircleMapper
Shortest red line denotes the movement between last two positions. Below the map shows:
TD.Bonnie had a heading of 304.1degrees (10.9degrees west of NorthWest) while traveling
a distance of 74miles(~119kilometres) over 3hours at a speed of ~25mph(~40km/h),
and was 262miles(~421kilometres) away from the coast in the direction of its heading.
^ A straightline projection does not forecast of what will happen in the future,
See blog1555post1853 for further explanation of what it does and doesn't do.
* DeepwaterHorizon is marked at 28.7N88.4W
Have a good morning everyone...I'll be back this afternoon to watch the naked girl...oops I mean cyclone ;)
Haha and thanks for your "teaching"!
Did I say it was?
Well good thing she did.
Although a nice breeze would have been nice...
New Orleans, Louisiana (Airport)
Updated: 15 min 55 sec ago
84 °F
Overcast
Humidity: 82%
Dew Point: 78 °F
Wind: 5 mph from the NNW
Pressure: 30.04 in (Rising)
The excuse, it's early in the season....won't apply much longer.
LOL!
LoL
So what you mean, Ike?
Sorry Ike, but this is still going to be an active season. Remember 2004? started in early August.
Last week of July looks like it will be...little to nothing in the Atlantic.
Now that you said that I am sure that we will have 99L before the end of the day :)
I hope so, as far as land-falling.
leaf blower
LOL...probably.
Bonnie(:
He still keeps his own blog going also. Took a peep in there the other day. Had some halfway decent wx graphics.
How so you know things will ramp up?
Hi Baha.
Neither did 2004.
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT SAT JUL 24 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
DEPRESSION BONNIE LOCATED ABOUT 215 MILES EAST-SOUTHEAST OF THE
MOUTH OF THE MISSISSIPPI RIVER.
A LARGE BUT DISORGANIZED AREA OF SHOWERS AND THUNDERSTORMS LOCATED
OVER THE CENTRAL CARIBBEAN IS ASSOCIATED WITH A TROPICAL WAVE
INTERACTING WITH AN UPPER-LEVEL LOW. DEVELOPMENT OF THE SYSTEM IS
NOT ANTICIPATED...AND THERE IS A LOW CHANCE...NEAR ZERO...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER ROBERTS/AVILA
Exactly but why above average?
Forget all they hype and casting.
If its below, then we are bored not having anything to follow, if its above, well, some of us may have trouble.
I hope for the best...period.
Bumbling Bonnie.
LOL
Look how Alex evolved? Became a category 2 storm with a pressure of a category 3-4 storm. Pressures are lower then normal in the Atlantic, plus there is alot of heat. The High pressure is setting up to be a player in the long term, once the Cape Verde systems get going, and they will as usual with every Hurricane Season. Wind shear should start to decrease as La-Nina gets stronger and also, with La-Ninas, I don't think there ever was a season with a below average of named storms. We will definitely get over 10 storms. I'm thinking about maybe one more this month, 5 in August, 7 in September, 3 in October, and maybe 1-2 in November and can't rule out a December storm. La-Ninas tend to give us late storms.
DEPRESSION BONNIE LOCATED ABOUT 215 MILES EAST-SOUTHEAST OF THE
MOUTH OF THE MISSISSIPPI RIVER.
Landfall in 11.9hrs :)
Near 0%???
Ha here we go, lol.
Waiting...
I knew I should have cut and pasted StormW's synopsis from yesterday's blog...
1 Tropical Storm ALEX 27 JUL- 2 AUG 45 1002 -
2 Hurricane BONNIE 19-31 AUG 100 954 3
RIP Bonnie. It's over.
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