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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Definitely. I wouldn't be surprised to see a year like 2008 impact-wise in the gulf which had 6 storms move through the gulf, and it could even be worse than that. We've already had 2 or 3 if you count TD 2. A couple of them will likely be majors, but we can hope to be lucky.
You know....no joke it's dang hard to hit Tampa directly with a hurricane. It really is. They will get one someday...impossible to say if it will be this year, but the month that they are most likely to get at least a direct impact from a major hurricane would be October, when storms are more likely to come into Florida from the southwest.
I have a hard time faulting people behaving responsibly. Yeah, this time it looks like it was more of an exercise. Next time it may not be.
Tampa missed it in 2004 by a degree or two change in Charley's course?
And what have you got against microscopes?
Its people like you that give people like me a pain, always harping on about the relative merits of bi-focal or uni-focal microbe viewing apparatus.
For your information, the Journal of American Microscope Lookers-Through have all the knowledge and experience that you dont have, and are the Authority on the matter.
I have been a lurker on this blog for 57 years and never heard you say one decent thing about microscopes.
Very sad. Poof!
How's that?
They're flying through the E side of the circulation right now. Top winds mostly unchanged.
If I was Levi's mom I would be very proud of such a smart son, and proud of his disposition and manners. He has been raised right.
Sheri
Thanks so much.... so still a depression.. but honestly... it wont take much for this thing to go up 5 mph
I was under the impression they never did recon over land, even in the US (Florida being a special case where it can make sense to do it).
Lol, well thank you :)
I do suppose it's true to be better safe than sorry, and with the oil situation I'm sure people will want to see advisories issued until they are sure it really is completely gone.
Thats pretty sweet! :)
If bonnie were a strong hurricane this would be bad news for New Orleans
Yeah they did get very lucky. That's exactly the kind of storm that can do it...coming over western Cuba from the southwest. It had the angle if it hadn't have curved in. I forget the numbers but I believe Tampa is almost as void of direct hits in the 20th and 21st century as the coast of Georgia is.
They dont fly over land...you sure it was a HH? There are many other bases with C-130s.
<--Survived a direct hit by Bonnie. I have to declare, I'm a Bonnie survivor.
Luckily... it isnt a strong hurr and definitely isnt on track to become one
microscope caster!
LOL
Yeah, I've always wondered why it is hard to hit the central coastline of Florida (Tampa area. Panhandle and southern Fl gets hit fairly frequently?????...but the last time a major hurricane hit here was 1920 I believe.
I am in N.O for a Bonnie Intercept.. Lets hope I can survive this beast! Lol!
I guess most systems a) don't have time to form once they hit cuba or b) get caught up in fronts that sweep/curve them south or take them north..or more west towards LA/Texas?
Yeah He does have good manners. More so than I do.. Maybe I should work on that... Lol...
Sorry everyone.... I do need to work on that.
True, I am expected T.D. Bonnie to hit Louisana as a Tropical Storm with winds around 40 - 50 mph. I also expect rain amounts to be around 1 - 3 inches. Otherwise no severe threat for damage or flooding. However anything can happen in the gulf of mexico when the conditions are right.
RDSL that was EPIC! :)
Well, think about it. Most storms are going to be moving from the east to west, so a strike from a Gulf storm on the west coast of Florida is somewhat unlikely. Much more likely for them to get a recurving storm from the South or one that crossed Florida and then recurves and hits again. I believe such a thing happened in the 60s, Donna, perhaps?
It's the shape of the coastline....SW Florida is facing SW and is easily hit by storms like Charley and Wilma. After you get to Tampa the coast switches to concave inward and heads northeast for a while, and if you have a storm coming out of the SSW, it can easily miss Tampa and head into the bight of Florida. The angle has to be so perfect....that's why they're hard to hit. The shape of the coastline is some of the same reason why Jacksonville, Florida and the Georgia coast are also so hard to hit.
A lot of it is just pure luck...and also the shape of the peninsula...most storms that come from the S will either turn NE into extreme SW FL (Wilma/Charley) or just move N-ward into the panhandle. You need a strong fall-like trough to catch it at just the right time.
I ate bon bons while watching Bonnie talking about Bonnie.
Yes,and had Charley hit where I live (Bradenton) or even an hour north in Tampa, Charley would of been a cat. 5. It went from a cat 1 to cat 4 in 6 hours.....and i think it had something to do with a loop eddy.. Fortunately, what a front, or trough curved it towards port Charlotte harbor. unfortnate for them, but thankfully it was moving fairly quickly. I remember tampa people going to orlando thinking they were safe, and getting slammed inland.
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If they don't fly over land, then how do they get from here to there. I'm not saying a dropsonde landed on my yard.
XD that would be cool if one did
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