Bonnie weakens to a tropical depression

By: Dr. Jeff Masters , 8:40 PM GMT on July 23, 2010

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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

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Quoting superweatherman:
so i guess nobody cares for the Wave of the cost of Puerto Rico then.? It is looking better and better by the minute. I even see banding starting to happen.



no 850mb vorticity and the system is split in half by one of the worst possible landmasses for a developing system to be near. The chances of this developing in the next 48 hours is near 0% for those reasons and high shear. Not surprised nhc didn't mention especially with a possible threat closer to home
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Quoting Hurricanes101:


obviously you care about his post or else you would not quote him all the time



heh i this poofed him
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Quoting Tazmanian:





no one cares about your post


obviously you care about his post or else you would not quote him all the time
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Quoting superweatherman:
so i guess nobody cares for the Wave of the cost of Puerto Rico then.? It is looking better and better by the minute. I even see banding starting to happen.



It's not an immediate threat, but is something interesting to watch over the next few days. I mentioned it a couple days ago and will continue tracking it.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
Couple web cams :)

http://www.sarasotasurf.com/accommodations/webcam.cfm

Several to choose from here as sunset approaches.

http://www.nbc-2.com/global/Category.asp?C=171057
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Quoting Tazmanian:



it most likey the TD is Fooling you your seeing thing



this storm is gone


No... Bonnie is far from Gone.... If they find even 30 mph it is STILL A TD.... And on radar you can clearly see it still has a closed low
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605. xcool
RECON head to center
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Levi32:


Hurrkat05, what's a trochoidal oscillation?


Its what happens when you use a Rotto Rooter :)
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Quoting hurrkat05:
LOOK GUYS IM NOT HEAR TO ARGUE OK IM JUST TELLING MY PEOPLE WHAT I SEE HAPPENING I COULD GIVE A RATS AZZ WHAT ANY OF THE REST OF YOU THINK...SO LETS JUST END THIS HERE ...DONT HAVE TIME TO PLAY AROUND...CONDITIONS CHANGE AND IF YOU DONT UNDERSTAND THAT THEN YOU SGHOULDNT BE HERE...READ MY POST THIS MORNING...





no one cares about your post
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so i guess nobody cares for the Wave of the cost of Puerto Rico then.? It is looking better and better by the minute. I even see banding starting to happen.

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better yet i wish they re move that dran quote
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If the NHC says Bonnie's still a cyclone, prob are it is.
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000
ABNT20 KNHC 232354
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT FRI JUL 23 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 45 MILES WEST-NORTHWEST OF FT. MYERS
FLORIDA.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN


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Quoting all4hurricanes:

Alex was already stronger than Melissa and 2007 had two cat Fives not exactly a bust
besides it's only July


he is a chronic downcaster that many have on ignore,

so please ignore him and move on and definitely don't quote him
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Quoting Levi32:


Hurrkat05, what's a trochoidal oscillation?
Oh! Oh! I think I know! Lol.
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Quoting IKE:


Can you please provide the link for recon?


NHC RECON page.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
One thing for sure,,ya cant always dismiss the low level circ of a Vigorus Vortex.

And to focus on the IR and Rainbow Sat Stills is BAD way to fly with a Spurious Low to Ones Se.

Everyone was watching the Upper Detach and swirl and stretch away to the NW around the ULL Tug.

The Culprit is at the surface.

Always has been.

Thats where they hang.


I wont ever take me eye off one like I did Elena in 85.

She turned around and Backtracked right over me when I did.
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no two?
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Quoting hurrkat05:
PATRAP LOOK FOR BONNIE TO START SLOWING DOWN IN THE NEXT 8 HOURS...HER SPEED WAS 20 MPH AND NOW ITS DOWN TO 17MPH AND THAT WILL CONTINUE TO DROP THROUGHOUT THE NIGHT...


Hurrkat, how many different people post under you handle? The tune you're singing is 180 degrees out of phase of what you were saying earlier........and you're back to caps...
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Quoting Levi32:


Hurrkat05, what's a trochoidal oscillation?

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Quoting wfyweather:
Guys, Bonnie is still a TD and deserves to be called that... I still has a closed circulation.. it still has td winds most likely... and it is firing brand new convection....



it most likey the TD is Fooling you your seeing thing



this storm is gone
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587. IKE
Quoting atmosweather:


Well RECON is about to pass through the center of this mess...they probably could have at least waited 10 minutes to find out.


Can you please provide the link for recon?
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Quoting fallinstorms:
the strongest storm this year will be no stronger then melissa of 2007

this is 2007 all over again

both were hype to be big

but had nada

Alex was already stronger than Melissa and 2007 had two cat Fives not exactly a bust
besides it's only July
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Guys, Bonnie is still a TD and deserves to be called that... I still has a closed circulation.. it still has td winds most likely... and it is firing brand new convection....
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584. xcool
storms love gom
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Levi32:


Hurrkat05, what's a trochoidal oscillation?


Shoot.. I consider myself well informed and I don't know that!
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580. IKE
Who are they fooling? Link

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Quoting pcbsmokey:
I believe Ike called that earlier.....open wave to LA


Hope this doesn't count with my "Oh no! When they get one we get the next one." Theory. Seriously though glad its not as bad as it could have been.
Member Since: August 15, 2008 Posts: 10 Comments: 3665
Quoting IKE:
RUKM?

...CENTER OF BONNIE EMERGES INTO THE EASTERN GULF OF MEXICO...
8:00 PM EDT Fri Jul 23
Location: 26.4°N 82.5°W
Max sustained: 35 mph
Moving: WNW at 17 mph
Min pressure: 1009 mb


Well RECON is about to pass through the center of this mess...they probably could have at least waited 10 minutes to find out.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
this storm is done gone it open in to a open wave
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Quoting hurrkat05:
PATRAP LOOK FOR BONNIE TO START SLOWING DOWN IN THE NEXT 8 HOURS...HER SPEED WAS 20 MPH AND NOW ITS DOWN TO 17MPH AND THAT WILL CONTINUE TO DROP THROUGHOUT THE NIGHT...





sorry too say this



but we got one downcaster and one wishcaster on the blog right now
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uh oh me no see defined ULL anymore
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Quoting atmosweather:


Hehehehe!


he will probably look it up on google
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Quoting hurrkat05:
PATRAP LOOK FOR BONNIE TO START SLOWING DOWN IN THE NEXT 8 HOURS...HER SPEED WAS 20 MPH AND NOW ITS DOWN TO 17MPH AND THAT WILL CONTINUE TO DROP THROUGHOUT THE NIGHT...


Thank you.

Well worth Noting too.

Pass the Tabasco Please.
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Quoting Levi32:


Hurrkat05, what's a trochoidal oscillation?


Hehehehe!
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Rut Roh,Roy Rodgers..!

LOL
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Quoting hurrkat05:
PATRAP SOONER OR LATER THEY WILLGET THE PICTURE BONNIE WILL SURPRISE LOTS IN HERE...BONNIE IS GETTING HER ACT TOGETHER...THIS IS GOING TO BE A TROPICAL STORM WITHIN THE NEXT 8 HOURS..STRONG CONVECTION IS BUILDING AROUIND THE CENTER AND ITS INCREASING LOOKS REALLY GOOD ON SAT PIC..



I hope not.


Henry's on Magazine is Having their 110 year Street Party tomorrow Uptown..

Rain O Shine.

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Quoting hurrkat05:
PATRAP SOONER OR LATER THEY WILLGET THE PICTURE BONNIE WILL SURPRISE LOTS IN HERE...BONNIE IS GETTING HER ACT TOGETHER...THIS IS GOING TO BE A TROPICAL STORM WITHIN THE NEXT 8 HOURS..STRONG CONVECTION IS BUILDING AROUIND THE CENTER AND ITS INCREASING LOOKS REALLY GOOD ON SAT PIC..


yesterday when it was actually a ts you said it was going to be nothing but rain and a couple of gusts. now that it is a disorganized tropical depression you are telling everybody it will become a ttropical storm
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this storm has had tell the nhc that tell them i said this storm is gone


RIP RIP RIP I WOUNDER IF THE NHC CAN READ
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Quoting louisianaweatherguy:
Pay attention to the flare-up just to the North of the COC... it's trying to come back...

whats the best way to see what the current shear is? It looks as though the ULL has slid more to the west recently and the shear has come down...

INTERESTING...


The shear is only increasing and the ULL is dominating the entire GOM and pumping dry air into Bonnie's circulation. No intensification can occur in these conditions.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
562. IKE
MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. BONNIE COULD REGAIN TROPICAL STORM STRENGTH AS IT MOVES
ACROSS THE GULF OF MEXICO.
AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT IS ENROUTE TO INVESTIGATE BONNIE.
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NHC doesn't want to let Bonnie go yet.

...CENTER OF BONNIE EMERGES INTO THE EASTERN GULF OF MEXICO...


SUMMARY OF 800 PM EDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...26.4N 82.5W
ABOUT 445 MI...715 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 45 MI...75 KM WNW OF FT. MYERS FLORIDA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/HR
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 17 MPH...27 KM/HR
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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