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 Patrap:
Itsa slowed in forward speed too.


and... its going west
Member Since: October 1, 2007 Posts: 81 Comments: 26511
1010. wxhatt
Quoting Chicklit:
Post #972 clearly shows the COC coming off Florida and spinning up into the new blob. Great Loop Patrick.


Speaking of new Blobs:

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Quoting MrstormX:


And it was an escalade! I hope they have insurance.
After I read this, I HAD to go back and see what the original post was.... lol
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Quoting MiamiHurricanes09:
And they just found 40mph winds... ok...


So what does all that mean?
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1007. Patrap
Itsa slowed in forward speed too.
Member Since: July 3, 2005 Posts: 426 Comments: 128654
So, let me get this right.

Since the vortex message was given, Bonnie has a closed circulation (although there isn't proof that it is). And they just found a SFMR reading of 40mph. Man, if the NHC takes this to a TS...
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Quoting wxhatt:


I know, I saw that an SUV fell into a sinkhole!



And it was an escalade! I hope they have insurance.
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Quoting Orcasystems:


Time: 01:51:00Z
Coordinates: 26.9667N 83.2667W
Acft. Static Air Press: 924.8 mb (~ 27.31 inHg)
Acft. Geopotential Hgt: 809 meters (~ 2,654 feet)
Extrap. Sfc. Press: 1014.3 mb (~ 29.95 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 93° at 36 knots (From the E at ~ 41.4 mph)
Air Temp: 20.0°C* (~ 68.0°F*)
Dew Pt: ////°C* (~ °F*)
Peak (10s) Flt. Lvl. Wind: 38 knots (~ 43.7 mph)
SFMR Peak (10s) Sfc. Wind: 35 knots (~ 40.2 mph)
And they just found 40mph winds... ok...
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1003. beell
sorry, 1900. lol, not lil, lol.
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AOI

AOI

AOI

AOI

Landfall Points

TS BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
1001. xcool
Time: 01:41:30Z
Coordinates: 26.4667N 83.1167W
Acft. Static Air Press: 925.0 mb (~ 27.32 inHg)
Acft. Geopotential Hgt: 784 meters (~ 2,572 feet)
Extrap. Sfc. Press: 1011.1 mb (~ 29.86 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 91° at 34 knots (From the E at ~ 39.1 mph)
Air Temp: 21.9°C* (~ 71.4°F*)
Dew Pt: ////°C* (~ °F*)
Peak (10s) Flt. Lvl. Wind: 38 knots (~ 43.7 mph)
SFMR Peak (10s) Sfc. Wind: 36 knots (~ 41.4 mph)
SFMR Rain Rate: 2 mm/hr (~ 0.08 in/hr)
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Post #972 clearly shows the COC coming off Florida and spinning up into the new blob. Great Loop Patrick.
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999. MZV
Naming dry-swirl Bonnie is payback for not naming 92L...
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Quoting atmosweather:


I don't get it either. They even passed through and around the center twice in 15 minutes to find any W winds and still couldn't.
Yep. If the NHC does keep it a tropical depression I don't know what they were looking at.
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997. xcool
TS .
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Quoting MrstormX:
TS Bonnie didn't amount to much of anything... it seems the storms in Milwaukee were more dangerous then this TC.


I know, I saw that an SUV fell into a sinkhole!

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Quoting MiamiHurricanes09:
Vortex message? The circulation is closed? Highest winds were recorded at 23 knots; not sufficient for tropical depression status.


;


Time: 01:51:00Z
Coordinates: 26.9667N 83.2667W
Acft. Static Air Press: 924.8 mb (~ 27.31 inHg)
Acft. Geopotential Hgt: 809 meters (~ 2,654 feet)
Extrap. Sfc. Press: 1014.3 mb (~ 29.95 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 93° at 36 knots (From the E at ~ 41.4 mph)
Air Temp: 20.0°C* (~ 68.0°F*)
Dew Pt: ////°C* (~ °F*)
Peak (10s) Flt. Lvl. Wind: 38 knots (~ 43.7 mph)
SFMR Peak (10s) Sfc. Wind: 35 knots (~ 40.2 mph)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
994. beell
Quoting 1900hurricane:

Extra-tropical transition cyclones?


Ok, a winner! (on a technicality). Good to see you have not lost any brain cells over summer vacation from AggieLand, lil.
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Quoting CybrTeddy:


Well that would kill the Hurricane season, but we'd all be gripped in a brutal cold winter season.. way worse than '09-10 winter.


Probably, and of course you can't overlook this stuff that is happening too. There is much going on for sure :)

http://spaceweather.com/

"Sunspot 1089 has grown so large, it can now be seen without the aid of a solar telescope."
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Quoting atmosweather:


I don't get it either. They even passed through and around the center twice in 15 minutes to find any W winds and still couldn't.


They're dang bored....they shouldn't even be out there wasting money on a system that is no longer a tropical cyclone.
Member Since: November 24, 2005 Posts: 635 Comments: 26654
Great post. BahaHurican could give the news.

It seems there is a lot of "blame" to be shared around in this situation. I think a culture of "laissez faire" permeated the minerals/oil prospecting industry during the Bush years, so that people / companies / agencies were pretty much guided by whatever personal principles they had. If they didn't have any or many, they could easily be subverted by those who only cared about how much money they could make
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Quoting MiamiHurricanes09:
Vortex message? The circulation is closed?


I don't get it either. They even passed through and around the center twice in 15 minutes to find any W winds and still couldn't.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting Chicklit:

He actually attributed something to something else; for example: DRY AIR INTRUSION FROM THE NORTH CENTRAL ATLANTIC IS FURTHER MAINTAINING THE UPPER LOW AND ENHANCING THE CONVECTION GENERATED BY IT.
He's telling not only what is happening but why.
Maybe that came from the suggestion box they put on the NHC page.
You may be right. I noticed that with a discussion Gladys Rubio did last week; well explained, referencing sources for conclusions, it didn't just "tell u what was there".
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Floater Infrared Channel 2 Loop
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Quoting wxhatt:


I've seen an ULL work it's way down to the surface and form a tropical system. Does that count?


My fav..

al La Claudette 09
Member Since: July 3, 2005 Posts: 426 Comments: 128654
TS Bonnie didn't amount to much of anything... it seems the storms in Milwaukee were more dangerous then this TC.
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Quoting HurricaneGeek:
I thought some people would like this page...

http://www.sat24.com


Also to see the tropical waves

http://www.sat24.com/af

I think this is the site that Jason, the man who always puts the African Satellite pictures up uses.
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Vortex message? The circulation is closed? Highest winds were recorded at 23 knots; not sufficient for tropical depression status.

000
URNT12 KNHC 240154
VORTEX DATA MESSAGE AL032010
A. 24/01:36:00Z
B. 26 deg 13 min N
083 deg 03 min W
C. 925 mb 782 m
D. 23 kt
E. 268 deg 1 nm
F. 051 deg 15 kt
G. 339 deg 5 nm
H. EXTRAP 1010 mb
I. 22 C / 764 m
J. 23 C / 765 m
K. 22 C / NA
L. NA
M. NA
N. 1345 / 9
O. 0.02 / 2 nm
P. AF305 0603A BONNIE OB 09
MAX OUTBOUND AND MAX FL WIND 44 KT N QUAD 01:47:00Z
SLP EXTRAP FROM 925 MB
MAX FL TEMP 23 C 089 / 6 NM FROM FL CNTR
;
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Quoting beell:


I think so. Still a good one to watch the interaction at the very least. Some ULL's are rumored to be a good thing for tropical cyclones. Most of the time-not, imo.

Can anybody name a cane that owed its existence to an ULL?

Extra-tropical transition cyclones?
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I thought some people would like this page...

http://www.sat24.com
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Quoting animalrsq:


Absolutely correct. And as far as the response, here is a perfect example. Jimmy Buffet donated a boat specifically designed for wildlife rescue over a week ago. It is still sitting in a parking lot because "they" can't figure out how to register and license it!! What???
This is when BP should be waving a few dollars to get things done in a hurry... LOL

But it seems there is no real sensitivity to the scope of the disaster they have caused, starting with the loss to their families of the eleven workers...
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Quoting Ossqss:


This is what I am keeping my eye on Pat. History ya know :)

http://en.wikipedia.org/wiki/Katla


Well that would kill the Hurricane season, but we'd all be gripped in a brutal cold winter season.. way worse than '09-10 winter.
Member Since: July 8, 2005 Posts: 259 Comments: 24173
Quoting Patrap:
The Atlantic been spitting out some weird stuff. Perfect ULL"s to dampen a Vortex with flavor,Alex with a Monsoon Gyre.

Whats next...?

Wave Zilla ?


I've seen an ULL work it's way down to the surface and form a tropical system. Does that count?
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Bonnie may be a blessing in disguise:

1) she arrives in a weakened state, but still sucks heat out of the spill area waters, depriving future storms of this energy

2) does so at low tide
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oops wrong time line still pretty cool looking though.
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Tropical Wave Bonnie?



What's with the vortex message they're only supposed to give those when there is a closed center.
Member Since: November 24, 2005 Posts: 635 Comments: 26654
Quoting BahaHurican:
Was thinking the same thing myself. They've lost a few of the veterans in the last little while, ayuh, but some of the new cadre seem to be making some strides...

He actually attributed something to something else; for example: DRY AIR INTRUSION FROM THE NORTH CENTRAL ATLANTIC IS FURTHER MAINTAINING THE UPPER LOW AND ENHANCING THE CONVECTION GENERATED BY IT.
He's telling not only what is happening but why.
Maybe that came from the suggestion box they put on the NHC page.
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Quoting Patrap:
The Atlantic been spitting out some weird stuff. Perfect ULL"s to dampen a Vortex with flavor,ALex with a Monsoon Gyre.
Whats next.

Wave Zilla?


This is what I am keeping my eye on Pat. History ya know :)

http://en.wikipedia.org/wiki/Katla

"Following the 2010 Eyjafjallajkull eruptions, on 20 April 2010 Icelandic President lafur Grmsson said "the time for Katla to erupt is coming close ... we [Iceland] have prepared ... it is high time for European governments and airline authorities all over Europe and the world to start planning for the eventual Katla eruption"."
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Since the Saints won the Super Bowl is this what they meant by hell freezing over? LOL
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Floater - RGB Color Infrared Loop
Member Since: July 3, 2005 Posts: 426 Comments: 128654
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I understand that July usually averages only one tropical cyclone, so Bonnie being #2 puts in line with the active season forcast.
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Quoting Chicklit:
Good Evening. Garcia did a nice job with the 8 p.m. Discussion tonight.


Was thinking the same thing myself. They've lost a few of the veterans in the last little while, ayuh, but some of the new cadre seem to be making some strides...
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The Atlantic been spitting out some weird stuff. Perfect ULL"s to dampen a Vortex with flavor,Alex with a Monsoon Gyre.

Whats next...?

Wave Zilla ?
Member Since: July 3, 2005 Posts: 426 Comments: 128654
Quoting BahaHurican:
It seems there is a lot of "blame" to be shared around in this situation. I think a culture of "laissez faire" permeated the minerals/oil prospecting industry during the Bush years, so that people / companies / agencies were pretty much guided by whatever personal principles they had. If they didn't have any or many, they could easily be subverted by those who only cared about how much money they could make.

I'm getting the impression from things I have read here and elsewhere that because the dollar was the bottom line a lot of safety measures that should have been put in place just were not there. Poor inspections by gov't officials so BP wouldn't have to pay so much to upgrade things; reduction of reinforcers in the concrete by Halliburton so BP wouldn't have to pay so much; turning off alarms so work would continue uninterrupted and BP wouldn't have to pay so much; all this while oil prices were driven to their highest level ever and BP could have afforded to pay the money that was needed to keep things being done safely. Now, in hindsight, BP looks to be paying more than it could ever have expected for it's short-cutting. But it was all part and parcel of a "group-think" that felt Big Oil should be able to do pretty much what it wanted.

That's why I laugh at people who castigate Mr. Obama for not doing enough quickly enough and who want to blame the oil spill problems on the Coast Guard. The problems that created this situation go so much deeper.... and have been going on for many, many years.


Absolutely correct. And as far as the response, here is a perfect example. Jimmy Buffet donated a boat specifically designed for wildlife rescue over a week ago. It is still sitting in a parking lot because "they" can't figure out how to register and license it!! What???
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Quoting jeffs713:

Look at the depth... all 500+ km down.


Yup, currently researching the history of 3- 7+ at that depth in such a short time. If you move the bottom the top will follow. Just sayin, that is big and deep.
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Stop Global Whining

Muzzle Tony Hayward
Member Since: July 3, 2005 Posts: 426 Comments: 128654
WVLoop
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963. beell
Quoting atmosweather:


That gradient of SE-erly upper winds is what is going to prevent Bonnie from vertically stacking and remaining a tropical cyclone.


I think so. Still a good one to watch the interaction at the very least. Some ULL's are rumored to be a good thing for tropical cyclones. Most of the time-not, imo.

Can anybody name a cane that owed its existence to an ULL?
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NEXRAD Radar
Tampa, Base Reflectivity 0.50 Degree Elevation Range 124 NMI

Member Since: July 3, 2005 Posts: 426 Comments: 128654
R.I.P. Tropical Storm Bonnie.

She gave much needed rain to Florida.
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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.