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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Gotta quit doubting myself, thanks guys.
So what does all this mean? Nothing? RIP?
Well the NHC sent out a vortex which means they've somehow found a closed circulation...but from the data given by the HH I don't see it. This is on the edge of being a remnant wave.
The pressure has been rising indicating a weakening cyclone, no west winds this is one of the worst TD's I have ever looked at, Ike you may not get much relief today from the heat.
There's hardly even much atmospheric moisture associated with the system anymore.
LOL there is a cute little swirl there.
Can say Bonnie has her swirl on.
Lack of sleep? lol.
Ehem. 2-4 feet of storm surge with oil can have a devastating impact on people living along the coast of SE LA and MS.
So no nice breeze in La either.
Oh well, she's been nice to watch and wonder from...
Do you think we will get that surge? I had read Alex put some surge/oil into LA. I hope not.
I agree, 2-4 ft would push alot into the marsh.
time for bouy check.
Thanks for all your help tonight/this morning.
So when do we get the info back? Not that it appears to matter at this point. Just curious...
Don't the tides have something to do with it too? Whether its high or low tide?
What is next on the watch list?
Bonnie will not even produce as much storm surge or wave action onto the N-ern Gulf Coast as Alex did.
Well that's good news.
112100 2610N 08637W 9249 00814 0151 +215 +169 271001 003 013 001 00
112130 2610N 08635W 9251 00813 0151 +215 +171 299002 003 012 001 00
112200 2610N 08634W 9249 00814 0151 +215 +173 287002 002 010 002 00
Noriega Point...JMHO :)
So where is TWC? lol. I saw them yesterday in S. Florida with nothing going on.
Almost as funny as Geraldo bending over halfway then getting attacked by a palm tree during Dennis!!!
Mike is down here on Dauphin Island, AL in between 2 cabins close to the west end
Yes during non-working hours...as much as possible.
My guess is as long as the swirl is visible on the visible, they'll keep it as a depression.
The rigs have already been evacuated, and there is no up side to having people return yet, even with the tiniest of odds of Bonnie flaring up. It would make them appear foolish. They're in a lose-lose situation, and erring on the side of cautious is the correct call.
I hope he/she is.
Doesn't look like it.
Dedicated to Bonnie...Link
Been looking for the ant hints, but explain why NO tree roaches or red wasps this year? The cold winter?
I know you were joking...
I think the scene in Gustave where he was bracing himself against the wind for a report, and he made it look like 100mph winds. Then two guys walked past behind him casually drinkin a beer was as funny :)
LMAO! have not heard that in ages.
LMAO its literally calm where Seidel is!!!
He in New Orleans?
Oh wow I missed that. Perhaps power was out by then. Saw him right before, crying that the levees may give out again.
Dennis for him was a classic. Even O'Reilly put it up on "ridiculous moments" or something similar.
Dauphin Island, AL. Zero movement of the plants in the sand.
YES! Do that, lol. I'll put the channel on now, lol.
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