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 GBguy88:


Just out of curiosity, not to stray from topic of current tropics...but have you ever been through a hurricane? For someone with such a passion for the tropics, you should try it sometime if you haven't :)


dude i went through wilmaa no lie i almost died ill tell story if u wanan hear?
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1509. GBguy88
Quoting Levi32:


Is that the only reason for liking them? I think not lol. I am fascinated by them. I know it's kind of ironic....but tropical weather is my favorite aspect of Meteorology. Winter storms were my first love until I saw Hurricane Isabel on satellite imagery in 2003 and I was hooked.


Just out of curiosity, not to stray from topic of current tropics...but have you ever been through a hurricane? For someone with such a passion for the tropics, you should try it sometime if you haven't :)
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Quoting cirrocumulus:
Small and compact, but the cloud tops just went higher.



Looks lime a lima bean. .. just sayin'.
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1507. scott39
Levi, have you looked at thr resent blowup of convection with Bonnie. Is it short lived or is something starting to happen around the LLC? Will it stick?
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Quoting chrisdscane:
when it says 0z that is the laTEesT RIGHT?>??


is it?
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1505. angiest
Quoting cirrocumulus:
Small and compact, but the cloud tops just went higher.



Is that a pinhole eye forming?



j/k
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Quoting Levi32:


Is that the only reason for liking them? I think not lol. I am fascinated by them. I know it's kind of ironic....but tropical weather is my favorite aspect of Meteorology. Winter storms were my first love until I saw Hurricane Isabel on satellite imagery in 2003 and I was hooked.


COOL can u link that imagry
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Quoting Levi32:


Eh....still a pretty shloppy mess lol. You could make a case for it still being a TD but it's on the edge.



LOL I know...very broad and disorganized LLC. I just wanted to sound surprised LOL!
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Small and compact, but the cloud tops just went higher.

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1501. angiest
Quoting cntrclckwiseSpenn:


Yeah, I've seen the DC nightmare on the history channel recently. That would be scary.

I've heard Tampa is sort of like New Orleans, in that it would be a bath tub type effect...


You want to know how scary that is? The would put Ft. Detrick under the gun. Ft. Detrick houses USAMRIID, site of one of the few biosafety level 4 labs in the country. BSL4 is where they work on nasty bugs like Ebola. Hopefully it is in a facility that can stand up to such things.

Interestingly, UTMB in Galveston has or will soon be bringing a BSL4 lab online.
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Quoting Levi32:


Is that the only reason for liking them? I think not lol. I am fascinated by them. I know it's kind of ironic....but tropical weather is my favorite aspect of Meteorology. Winter storms were my first love until I saw Hurricane Isabel on satellite imagery in 2003 and I was hooked.



40KT OF SHEAR OVER N.O
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A near Earth asteroid (1999 JD6) will pass within 50 lunar distances on July 27. Its estimated size is roughly 2 kilometers in diameter.

NASA Jet Propulsion Laboratory

SpaceWeather.com

How close should we be watching the cloudiness and slight turning just north of Hispaniola, or is it mostly mid and upper level? The cloudiness has maintained over the last several frames.

It also appears the dry air from the Upper Level Low in the western Gulf of Mexico is being cutoff by moisture from the south. Should one expect strengthening from Bonnie?
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1496. Levi32
Quoting atmosweather:
Pressure still seems to be rising...but W winds!!!


Eh....still a pretty shloppy mess lol. You could make a case for it still being a TD but it's on the edge. Center is very ill-defined.

Member Since: November 24, 2005 Posts: 635 Comments: 26701
when it says 0z that is the laTEesT RIGHT?>??
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1494. Levi32
Quoting chrisdscane:


so y would u like hurricanes ones never going to hit u?


Is that the only reason for liking them? I think not lol. I am fascinated by them. I know it's kind of ironic....but tropical weather is my favorite aspect of Meteorology. Winter storms were my first love until I saw Hurricane Isabel on satellite imagery in 2003 and I was hooked.
Member Since: November 24, 2005 Posts: 635 Comments: 26701
Pressure still seems to be rising...but W winds!!!
Member Since: September 24, 2005 Posts: 33 Comments: 9265
1491. JLPR2
Quoting Levi32:
0z GFS Parallel continues to show the potential for home-grown mischief off the SE US coast during the first week of August, as well as our first Cape Verde storm.



Just keep that Cape Verde Storm away from me! :)
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Quoting Levi32:


I do.


so y would u like hurricanes ones never going to hit u?
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1489. JLPR2
Quoting Jeff9641:
A spurious low south of the DR????Could be a sneaky feature developing...

http://cimss.ssec.wisc.edu/tropic2/real-time/windmain.php?&basin=atlantic&sat=wg8%u220F=ir& ;zoom=&tim e=


Actually vorticity is to the North of Hispaniola


Its interesting cause its under low shear because an ULL is almost aligned with the 850vorticity, weird. XD
Maybe we could get a Subtropical storm
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Quoting angiest:


Most of the town has now been taken over by Matagorda Bay. I would like to visit the place sometime (its just a couple of hours down the coast).

Two of the absolute worst case scenarios would have to be hurricanes striking either the west end of Long Island or tracking up the west side of Chesapeake Bay.


Yeah, I've seen the DC nightmare on the history channel recently. That would be scary.

I've heard Tampa is sort of like New Orleans, in that it would be a bath tub type effect...
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1487. Levi32
0z GFS Parallel continues to show the potential for home-grown mischief off the SE US coast during the first week of August, as well as our first Cape Verde storm.

Member Since: November 24, 2005 Posts: 635 Comments: 26701
1486. xcool
scott39 .i guess she not dead hmmm
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1485. Levi32
Quoting chrisdscane:


u live ina alska


I do.
Member Since: November 24, 2005 Posts: 635 Comments: 26701
1483. angiest
Quoting CosmicEvents:
At the moment Bonnie(TD3) has to go down as the cutest little TD or TS in history(sat. view in post 1469). Let's hope she stays that way.


Thinking smaller than Marco now if they upgrade?
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Quoting Levi32:


I know, in fact we have a pretty dang good airbase in Anchorage, but I have never had one come over Homer, where I live, 230 miles south of there.


u live ina alska
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At the moment Bonnie(TD3) has to go down as the cutest little TD or TS in history(sat. view in post 1469). Let's hope she stays that way.
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Quoting Levi32:


With these water temperatures....definitely.





record high atlantic water temps, Levi?
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1479. angiest
1471 - Those SFMR measurements don't seem to count with Bonnie, as they had those with her for several hours before naming.
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Woohoo Bonnie has a single thunderstorm haha. Time to run away j/k.
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1476. Levi32
Quoting cntrclckwiseSpenn:


I am not familiar, but this does not surprise me...

Would not be surprised to see New York City get hit by a major hurricane.


With these water temperatures....definitely.



Member Since: November 24, 2005 Posts: 635 Comments: 26701
1475. scott39
Quoting xcool:
Looks like we may have a little somethin, somethin there Xcool!
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Bonnie update: Convection forms around the western half.

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1473. angiest
Quoting cntrclckwiseSpenn:


I am not familiar, but this does not surprise me...

Would not be surprised to see New York City get hit by a major hurricane.


Most of the town has now been taken over by Matagorda Bay. I would like to visit the place sometime (its just a couple of hours down the coast).

Two of the absolute worst case scenarios would have to be hurricanes striking either the west end of Long Island or tracking up the west side of Chesapeake Bay.
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Quoting cirrocumulus:
It's climatology. The troughs are at typical tilts during the various times of the season and the storms correspond to the averages. Once in a blue moon, the hurricane may take an unlikely path. Tampa is less out of the woods than the dry zone about 100 miles north. Though this season, anything is possible more than at other times.


Does this imply Tampa may be in the woods this year opposed to a "normal" season?
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Time: 04:51:30Z
Coordinates: 26.7167N 83.8333W
Acft. Static Air Press: 925.1 mb (~ 27.32 inHg)
Acft. Geopotential Hgt: 797 meters (~ 2,615 feet)
Extrap. Sfc. Press: 1012.8 mb (~ 29.91 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 136° at 35 knots (From the SE at ~ 40.2 mph)
Air Temp: 22.0°C* (~ 71.6°F*)
Dew Pt: ////°C* (~ °F*)
Peak (10s) Flt. Lvl. Wind: 36 knots (~ 41.4 mph)
SFMR Peak (10s) Sfc. Wind: 36 knots (~ 41.4 mph)
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting Levi32:


Yeah....well I can't be completely sure they haven't been near Homer. We have a military plane that practices in our airspace all the time here, but I wouldn't know what type it is. It doesn't look like a C-130 though.

Probably a C-17...
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1469. xcool
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Quoting angiest:


Are you familiar with the history of Indianola, TX? Once rivaled Galveston until destroyed by two major hurricanes within a dozen years in the latter half of the 19th century. Now just some ruins and a historical marker.


I am not familiar, but this does not surprise me...

Would not be surprised to see New York City get hit by a major hurricane.
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1467. Levi32
Quoting cgmaddog:


Levi, The coast guard flys C-130 all of the time to anchorage from Kodiak

Mike


Yeah....well I can't be completely sure they haven't been near Homer. We have a military plane that practices in our airspace all the time here, but I wouldn't know what type it is. It doesn't look like a C-130 though.
Member Since: November 24, 2005 Posts: 635 Comments: 26701
Quoting GBguy88:


I think Pensacola would have been the oldest settlement in the country, but was destroyed (or severely disrupted) by a hurricane early in the 1500s. I think it's St. Augustine with the title now. Could be wrong.
I believe you are correct.
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It's climatology. The troughs are at typical tilts during the various times of the season and the storms correspond to the averages. Once in a blue moon, the hurricane may take an unlikely path. Tampa is less out of the woods than the dry zone about 100 miles north. Though this season, anything is possible more than at other times.
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Quoting Levi32:


Well I've never seen a C-130 in Alaska lol.


Levi, The coast guard flys C-130 all of the time to anchorage from Kodiak

Mike
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1463. Levi32
Quoting HaboobsRsweet:

You have two Air Force bases up there...they have been there.


I know, in fact we have a pretty dang good airbase in Anchorage, but I have never had one come over Homer, where I live, 230 miles south of there.
Member Since: November 24, 2005 Posts: 635 Comments: 26701
Quoting Levi32:


Well I've never seen a C-130 in Alaska lol.

You have two Air Force bases up there...they have been there.
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1461. angiest
Quoting cntrclckwiseSpenn:


Galveston used to be a major city until it was hit by a hurricane....


Are you familiar with the history of Indianola, TX? Once rivaled Galveston until destroyed by two major hurricanes within a dozen years in the latter half of the 19th century. Now just some ruins and a historical marker.
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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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