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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If there actually is a tornado on the ground, this could get bad.

TORNADO WARNING
NJC003-013-017-031-NYC005-047-061-081-240045-
/O.NEW.KOKX.TO.W.0006.100724T0012Z-100724T0045Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE NEW YORK NY
812 PM EDT FRI JUL 23 2010

THE NATIONAL WEATHER SERVICE IN UPTON NY HAS ISSUED A

* TORNADO WARNING FOR...
QUEENS COUNTY IN SOUTHEAST NEW YORK...
PASSAIC COUNTY IN NORTHEAST NEW JERSEY...
KINGS (BROOKLYN) COUNTY IN SOUTHEAST NEW YORK...
NEW YORK (MANHATTAN) COUNTY IN SOUTHEAST NEW YORK...
BRONX COUNTY IN SOUTHEAST NEW YORK...
NORTHEASTERN ESSEX COUNTY IN NORTHEAST NEW JERSEY...
BERGEN COUNTY IN NORTHEAST NEW JERSEY...
HUDSON COUNTY IN NORTHEAST NEW JERSEY...

* UNTIL 845 PM EDT...

* AT 808 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR PATERSON...
MOVING SOUTHEAST AT 30 MPH.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
PARAMUS...BLOOMFIELD...PASSAIC...ORADELL...HACKENSACK...
RUTHERFORD...BERGENFIELD...TETERBORO...LYNDHURST...ENGLEWOOD...
SECAUCUS...RIDGEFIELD...FORT LEE...RIVERDALE...UNION CITY...
MORNINGSIDE HEIGHTS...HOBOKEN...UPPER WEST SIDE...HARLEM...CENTRAL
PARK...MIDTOWN MANHATTAN...MOTT HAVEN...SOHO...EAST VILLAGE...EAST
TREMONT...BATTERY PARK...LOWER EAST SIDE...LONG ISLAND CITY...
BROOKLYN HEIGHTS...WHITESTONE...TRIBOROUGH BRIDGE...RFK BRIDGE...
THROGS NECK BRIDGE...LAGUARDIA AIRPORT...JACKSON HEIGHTS...
FLUSHING...CROWN HEIGHTS...CO-OP CITY AND ASTORIA

PRECAUTIONARY/PREPAREDNESS ACTIONS...

WHEN A TORNADO WARNING IS ISSUED BASED ON DOPPLER RADAR...IT MEANS
THAT STRONG ROTATION HAS BEEN DETECTED IN THE STORM. A TORNADO MAY
ALREADY BE ON THE GROUND...OR IS EXPECTED TO DEVELOP SHORTLY. IF YOU
ARE IN THE PATH OF THIS DANGEROUS STORM...MOVE INDOORS AND TO THE
LOWEST LEVEL OF THE BUILDING. STAY AWAY FROM WINDOWS. IF DRIVING...DO
NOT SEEK SHELTER UNDER A HIGHWAY OVERPASS.

THE SAFEST PLACE TO BE DURING A TORNADO IS IN A BASEMENT. GET UNDER A
WORKBENCH OR OTHER PIECE OF STURDY FURNITURE. IF NO BASEMENT IS
AVAILABLE...SEEK SHELTER ON THE LOWEST FLOOR OF THE BUILDING IN AN
INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE BLANKETS OR PILLOWS TO
COVER YOUR BODY AND ALWAYS STAY AWAY FROM WINDOWS.

IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A
SUBSTANTIAL SHELTER. IF NO SHELTER IS AVAILABLE...LIE FLAT IN THE
NEAREST DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS.

&&

LAT...LON 4091 7430 4090 7428 4092 7429 4094 7428
4097 7429 4107 7420 4087 7378 4086 7380
4084 7380 4082 7378 4080 7378 4065 7393
4090 7433
TIME...MOT...LOC 0011Z 306DEG 25KT 4092 7417

$$

DSW
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Blog slowed down a bit. Did the trolls leave?

My weather radio faithfully woke me up at 4:45-ish this morning to alert me to a TS watch that I knew was coming anyway.

I need some sleep tonight. If it goes off tonight it had better be for something worthwhile.
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Tornado Warning for New York City
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Quoting nrtiwlnvragn:


Seems to be a fancy phrase for wobbles along the path.
Well that makes it a lot easier, lol.
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Neither the SPC or HPC seems to think of Bonnie highly:



Not even a 5% "See Text" and...



...no mention of even slight risk of exceeding Flash Flood guidance!
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Quoting MiamiHurricanes09:
I know trochoidal means, "Permit rotation".


Seems to be a fancy phrase for wobbles along the path.
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Based on recon, Bonnie remains a tropical depression.
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Quoting Hurricanes101:


closed circulation found + winds of 35mph found = Bonnie is still a depression; despite the appearance on satellite


Can't argue with that...although the W-erly and NW-erly winds only seem to extent out about 5-10 miles.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting CaneWarning:
hurrkat05, thank you for being such a tremendous asset to this blog. We all appreciate your expertise!!!


Still laughing Cane........Hurrkat has no sense of sarcasm.......LOL
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well convection is re firing up over the center.. so
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Bonnie still has a closed circulation, and it really was quite obvious on visible imagery. The westerlies are weak and it will probably open up into a wave eventually, but not yet.

Member Since: November 24, 2005 Posts: 635 Comments: 26699
Quoting atmosweather:
Couple of W-erlies found...looks like the center is near 26.2N 82.6W
Never mind, ya' fixed it.
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647. beell
Quoting 1900hurricane:

And obviously you care about his post that he posted about his post about him.

Which would mean that I obviously care about your post about his post that he posted about his post about him...?


Thank you-you were right on cue, LOL.
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6 Earthquakes in Mindanao, Philippines in less than 2 hours.


Link
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Quoting atmosweather:
Couple of W-erlies found...looks like the center is near 26.2N 86.6W


closed circulation found + winds of 35mph found = Bonnie is still a depression; despite the appearance on satellite
Member Since: March 10, 2010 Posts: 1 Comments: 7874
631: Lather, Rinse, Repeat...

Bonnie not dead, but looking seriously injured. Maybe some rain Saturday evening, but not concerned at all right now. I'll keep an eye on her overnight, but I think she's moving too fast to get her act together. She may make TS by landfall, or she could be a big surprise. But at present I'm not concerned at all.

I'm going to go sti by the pool for a while, the Trolls are killing my patience.
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Couple of W-erlies found...looks like the center is near 26.2N 82.6W
Member Since: September 24, 2005 Posts: 33 Comments: 9265
640. SLU
Bonnie's had a very rough day at the office. She needs to re energize quickly or else risk being declared post-tropical.

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Quoting MiamiHurricanes09:
I know trochoidal means, "Permit rotation".


I think it has sumffin to do with a toilet
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COC found; pressure up to 1010mb.

000
URNT15 KNHC 240005
AF305 0603A BONNIE HDOB 16 20100723
235530 2623N 08258W 9249 00794 0124 +217 //// 045026 027 030 001 01
235600 2622N 08257W 9250 00794 0125 +215 //// 047026 027 030 001 01
235630 2621N 08256W 9246 00797 0125 +213 //// 042027 028 029 001 01
235700 2620N 08255W 9250 00792 0125 +213 //// 042029 029 029 001 01
235730 2619N 08254W 9249 00793 0123 +215 //// 041030 030 030 000 01
235800 2617N 08253W 9251 00791 0121 +217 //// 038027 028 030 001 01
235830 2616N 08251W 9246 00794 0119 +220 +220 032025 027 029 001 03
235900 2615N 08250W 9248 00792 0119 +220 //// 026022 024 028 002 01
235930 2614N 08249W 9249 00790 0118 +222 //// 018021 022 030 001 01
000000 2613N 08247W 9248 00790 0118 +219 //// 008021 022 026 002 05
000030 2613N 08245W 9249 00790 0117 +220 //// 005017 018 027 001 01
000100 2612N 08243W 9249 00787 0116 +215 //// 354018 019 027 000 05
000130 2612N 08242W 9251 00782 0113 +216 //// 335013 014 028 002 05
000200 2613N 08240W 9245 00787 0107 +226 //// 305011 016 026 002 05
000230 2614N 08239W 9254 00776 0102 +239 +223 293004 006 017 000 03
000300 2616N 08238W 9246 00782 0104 +227 //// 085011 017 015 000 05
000330 2616N 08240W 9246 00782 0104 +227 +227 070013 015 017 002 03
000400 2615N 08241W 9259 00771 0106 +222 //// 031013 016 025 001 01
000430 2614N 08243W 9250 00785 0111 +222 //// 353017 019 028 000 01
000500 2612N 08244W 9248 00791 0116 +222 //// 350017 020 026 000 01
$$
;
Member Since: Posts: Comments:
Quoting beell:


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


I dont have Taz on ignore though, I do have the troll he keeps responding to on ignore however, as I am sure most of us do
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting 1900hurricane:

And obviously you care about his post that he posted about his post about him.

Which would mean that I obviously care about your post about his post that he posted about his post about him...?


There is reason to be concerned about this... the winds could down branches in such.... no big deal... but up to 5 inches of rain is possible in a short period of time... that can cause flash flooding.... and tornadoes will be possible througout tomorrow
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Quoting Rainwalker:
Is the mass of convection south east of Haiti a wave or just "convection"


Just convection associated with good upper divergence
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting MiamiHurricanes09:
LOL, I'm not to familiar with it but I believe that it involves friction pulling a vortex away, ahhh, I don't know! LOL, maybe Levi can explain.
I know trochoidal means, "Permit rotation".
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Quoting beell:


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

And obviously you care about his post that he posted about his post about him.

Which would mean that I obviously care about your post about his post that he posted about his post about him...?
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recon is finding winds that still would classify this as a depression

no matter what you would say about the appearance, if she still has west winds, Bonnie is still a depression
Member Since: March 10, 2010 Posts: 1 Comments: 7874
hurrkat05, thank you for being such a tremendous asset to this blog. We all appreciate your expertise!!!
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Quoting Tazmanian:
and how can you tell from the rader it has a closed low its olny a rader


rader dont find closed low


No it doesn't... but if you are smart you can figure it out. You can clearly see the center.... and rain wrapping around that on the Northern Side. We are clearly still dealing with a Tropical Depression....
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Bonnie is coming right for me and I am far from concerned...seen thunderstorms with stronger winds and more rain in a shorter period of time. Just another rainy day on the coast.
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Quoting 1900hurricane:

Wow, never heard of that model before. I think it says that it's experimental, correct?


I would guess so.
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624. xcool
jasoniscoolman2010x old
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Is the mass of convection south east of Haiti a wave or just "convection"
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Quoting jasoniscoolman2010x:



old
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Quoting CybrTeddy:


Shoot.. I consider myself well informed and I don't know that!
LOL, I'm not to familiar with it but I believe that it involves friction pulling a vortex away, ahhh, I don't know! LOL, maybe Levi can explain.
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Quoting BenBIogger:
FIMZ Shows tropical development.

66 Hrs


114 Hrs



Wow, never heard of that model before. I think it says that it's experimental, correct?
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617. beell
Quoting Hurricanes101:


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


obviously you care about his post about him or else you would not quote him
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and how can you tell from the rader it has a closed low its olny a rader


rader dont find closed low
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Anyone have the most recent pages for the tropical waves in the region.
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FIMZ Shows tropical development in the NW Caribbean.

66 Hrs


114 Hrs


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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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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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