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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92L
Alex
95L
Bonnie
STRENGTHENING BEFORE BONNIE REACHES THE NORTHERN GULF COAST. AN INCREASINGLY LIKELY ALTERNATIVE SCENARIO IS THAT THE CYCLONE WILL DECAY TO A REMNANT LOW OR OPEN TROUGH SOMETIME ON SATURDAY.
So remant low forecast does follow NHC, sorry.
(Straightline^projection using its last 2 positions. Take with HUGE grain of salt)
Copy&paste 25.8N81.1W, 26.2N81.9W, 26.4N82.5W-26.4N83.4W, 26.4N83.4W-25.8N97.2W, 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 270.2degrees (0.2degrees north of dueWest) while traveling
a distance of 56miles(~90kilometres) over 3hours at a speed of ~19mph(~30km/h),
and was 858miles(~1,381kilometres) away from the coast in the direction of its heading.
^ Straightline projections are not forecasts of what will happen in the future,
especially not for TropicalCyclones. They aftcast what has already happened.
* DeepwaterHorizon is marked at 28.7N88.4W
If NHC went with the TS winds found in TD2 right before landfall we'd be looking at 5 named storms right now.
Iowa, Pennsylvania, New York. hold on to your hats, its gonna be a restless night. Gracious thats a big MCC in MINN, SD...
Relocation or is Bonnie falling apart?
AOI
Nope. In the end their forecast is for intensification.
FORECAST POSITIONS AND MAX WINDS
INITIAL 24/0300Z 26.4N 83.4W 30 KT
12HR VT 24/1200Z 27.7N 85.7W 30 KT
24HR VT 25/0000Z 29.2N 88.5W 35 KT
36HR VT 25/1200Z 30.5N 90.5W 35 KT...INLAND
48HR VT 26/0000Z 31.4N 91.8W 25 KT...INLAND
72HR VT 27/0000Z 34.0N 93.0W 20 KT...POST-TROP/REMNT LOW
96HR VT 28/0000Z...DISSIPATED
maybe new area big to follow
or worse.. the dreaded almost westerly winds.
Believe this means we have seen the end.
Well, I would need to do a complete autopsy to detirmine the Time OfDeath.
If it can be shown that the Equine was alive BEFORE the Hammer incident, charges may be laid in this matter.
Hello there?
I'm sorry... I didn't know you could see the future? the convection has already fired up once... It can do it again
Hey finally someone I completely agree with. 2 months gone by and all we have is one hurricane and one cluster of thunderstorms that they named just so they can pretend it is an active year
There you go.
So technically we're still on course for an 18 - 23 year.
In all seriousness the numbers have been messed up badly already this year if we have to go strictly by the book which we should anyway ...
NEXRAD Radar
Sioux Falls, Base Reflectivity 0.50 Degree Elevation Range 248 NMI
You are right on that,,,, oh my!
2. It is moving further West than most models showed... hopefully that stops so I can have a a successful intercept in New Orlenas
TONS of TVS popping everywhere, lucky none that have been sustained very long, yet...
in the end their mostly right u gota admit
There were several storms in 2009 that should have been classified.. 90L and 91L most noticeably in Late May - Early June. 2009 should have had 11 named storms imo. 2008 should have had 17, there was a low off the coast of the East coast that was organized enough that the hurricane hunters sent a vortex message, never became a named system. But they are the NHC, they know what they're doing.
Not at all...I am going by what I see and what I know is causing it. If I am wrong I will always take it in stride.
LOL
doesnt matter what it looks like man... there finding strong enough winds and a closed circ.... case closed
Its the wundergrounds radar.
Mines in the truck..But the Doppler Dish is Cracked..
again
Not seeing a closed circulation............
Danny from last year looked worse than this.
FORECASTED BY THE SHORT RANGE MODELS TO MOVE WEST NORTHWEST AND
THROUGH SOUTH FLORIDA ON SATURDAY. AT THE SAME TIME...THE DEEP
TROPICAL MOISTURE WILL REMAIN IN PLACE WITH PWAT VALUES AROUND 2.2
TO 2.4 INCHES. SO HAVE INCREASE THE POPS A LITTLE BIT TO NUMEROUS
CONDITIONS OVER ALL OF THE CWA ON SATURDAY ALONG WITH LOCALLY
HEAVY RAINFALL.
ANOTHER TROPICAL WAVE OVER THE EASTERN CARIBBEAN SEA WILL ALSO
MOVE TO THE WEST NORTHWEST AND THROUGH SOUTH FLORIDA LATE SUNDAY
INTO MONDAY. THIS WILL KEEP THE TROPICAL MOISTURE IN PLACE ALONG
WITH SCATTERED POPS FOR SUNDAY AND MONDAY.
hmmmm?
Yeah I remember those systems very well.
I guess they don't want to go about naming every blob on the satellite pics but if a systems meets the specifications then it should be classified accordingly.
I'd like to see less confusion in years to come. It's been happening a lot more these days than say 10 years ago which it strange giving that we have more technology and research to aid us.
theres a closed circulation... Look at HH obs they found west winds.. its a td.
U serious? ITS SHOWING LITTLE PRCIP BECAUSE ITS OVER WATER AND FAR FROM THE RADAR SITE!
1" maybe locally 2" if that.
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