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 Tazmanian:
round 1


90L bust

91L bust

92L bust

93L be comes Alex

94L bust

95L bust

96L be comes TD 2

97L be comes TS Bonnie

98L bust but may be upgrade at post season



we are still on round 1

99L still awaits us.
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Quoting homelesswanderer:
Speaking of preparedness. I just heard about a thing you plug into your cars lighter/accessory port and you can plug things into like a regular house plug. Think they're called converters? Anyway sounds like a neat thing to have. I'm probably the last person on the planet to know about this. :)
OK for CHARGING batteries on laptops, cell phones etc but not recommended to attempt to operate electronics. I've got one and when I am on a run I will turn off my computer or phone and charge them up but when I turn them on I make sure they are disconnected.
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I believe Ike called that earlier.....open wave to LA
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Quoting Levi32:


A hint at things to come.


Understandable though it is 16 days out.
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Floater - RGB Color Infrared Loop
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Recon descending.

000
URNT15 KNHC 232315
AF305 0603A BONNIE HDOB 11 20100723
230530 2744N 08458W 4824 06201 0366 -056 -101 149015 016 003 000 03
230600 2745N 08456W 5050 05842 0341 -040 -067 133015 016 /// /// 03
230630 2746N 08453W 5272 05496 0321 -028 -037 142013 015 002 000 03
230700 2747N 08451W 5273 05504 0323 -021 -038 143013 013 001 000 00
230730 2748N 08450W 5288 05478 0321 -020 -039 143013 014 002 000 00
230800 2748N 08448W 5278 05494 0322 -020 -038 139014 015 007 000 03
230830 2749N 08446W 5285 05484 0322 -025 -033 136016 016 003 000 03
230900 2750N 08445W 5265 05515 0323 -021 -037 134016 017 004 000 00
230930 2750N 08443W 5353 05393 0322 -015 -035 134020 022 002 001 00
231000 2751N 08441W 5601 05026 0125 -002 -010 129025 028 011 000 00
231030 2752N 08439W 5731 04837 0135 +005 //// 130029 031 011 000 01
231100 2752N 08438W 5931 04566 0142 +019 //// 122031 032 015 001 05
231130 2753N 08436W 6157 04264 0149 +036 //// 110030 031 017 000 01
231200 2754N 08434W 6346 04019 0148 +053 +047 106029 031 018 000 03
231230 2755N 08432W 6642 03648 0176 +060 +057 097019 021 /// /// 03
231300 2755N 08430W 6937 03286 0169 +088 +059 096018 019 /// /// 03
231330 2756N 08428W 7309 02853 0176 +111 +076 085019 024 /// /// 03
231400 2758N 08427W 7704 02409 0180 +138 +033 054031 034 /// /// 03
231430 2800N 08429W 8042 02044 0180 +158 +005 051032 033 /// /// 03
231500 2801N 08431W 8418 01643 0165 +186 -004 057027 029 /// /// 03
$$
;

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Quoting earthlydragonfly:


So they might not know that you have them on ignore?? Unless you say Poof of course..
But that's the beauty... there they are, nattering away, and u can't hear a thing.... BWAhahahaha.....

LOL
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Quoting MiamiHurricanes09:
Based on surface observations and radar loops the surface circulation of Bonnie looks ill-defined. I believe that they will find TD force winds, but not a closed surface circulation.


Well they just turned around and climbed from 850mb...either they've found mechanical difficulty or they are scrubbing it because there's no longer a TC to fly into.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting WeatherNerdPR:

Most likely it isn't.



trust me its gone
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Quoting scott39:
What round we in now? I think Bonnie will put on one more little show!


Round 8.

The Gurl just Did the Walk wit da Round Card too.


Bonnie,,cut and battered.,

Seems to have a Lil Bounce in her step coming out the corner.

Ding,Ding!!!!
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Quoting CybrTeddy:
I'm willing to bet this is no longer a tropical cyclone.


Most likely it isn't.
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round 1


90L bust

91L bust

92L bust

93L be comes Alex

94L bust

95L bust

96L be comes TD 2

97L be comes TS Bonnie

98L bust but may be upgrade at post season



we are still on round 1
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Quoting CybrTeddy:
I'm willing to bet this is no longer a tropical cyclone.

bonnie no more its an open wave and thats even dispating rapidly
Member Since: July 15, 2006 Posts: 169 Comments: 53296
from the Author here,

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.
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Chew Mail Pouch
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Quoting Patrap:


Someone is Priming the Carburetor seems.

Must be tapping the Spill fuel..

What round we in now? I think Bonnie will put on one more little show!
Member Since: June 13, 2009 Posts: 0 Comments: 6743
Quoting KEEPEROFTHEGATE:


going going ....



gone
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Quoting Patrap:
Ouick,..get the Paddles,!,

and CLEAR !!!!


"Cha..Chunk"..

Beep,..beep,...beep..beep..






lmao! yep we do have a pulse, I don't think she will flatline again until late tomorrow or Sunday morning.
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Quoting WeatherNerdPR:

Still you get what I mean.



yes
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Quoting CybrTeddy:
I'm willing to bet this is no longer a tropical cyclone.

Likely yes.
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18z GFS Parallel still showing the potential for homegrown mischief during the first week of August off the SE US coast and in the northern Gulf of Mexico as the mean trough over the Canadian Maritimes sends down a couple fronts to get stalled under the nose of an upper ridge, a conducive pattern for warm-core lows to develop.

Day 11:

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Quoting CybrTeddy:
I'm willing to bet this is no longer a tropical cyclone.



Dont poke a Bear before its Mounted..,

on da wall.
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Quoting CybrTeddy:
I'm willing to bet this is no longer a tropical cyclone.




yup


it RIP
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Quoting Patrap:
Ouick,..get the Paddles,!,

and CLEAR !!!!


"Cha..Chunk"..

Beep,..beep,...beep..beep..







Is that a small flare up I see? Is it safe to assume she's not a zombie?
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going going ....
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting Tazmanian:



try more like 11pm

Still you get what I mean.
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I'm willing to bet this is no longer a tropical cyclone.

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431. JLPR2
Quoting MiamiWarnings:
jp, then i guess i saw the operational then?



Parallel:


Operational:
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Quoting WeatherNerdPR:

So at 8 the headline should say "BONNIE DEGENERATES TO A REMNANT LOW" , right?
They'll probably keep it a tropical depression until the reconnaissance aircraft investigates, if recon finds and open low or winds below tropical depression force they'll probably downgrade it at 11 P.M.
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Atmo I was a big believer in Bonnie getting stronger before it hit S. Fl. but late yesterday if you looked at the water vapor it got squashed by dry air from the east as it was finally getting a little distance from the ull. You could see the little devil get put into the dry air vise and that what you picked up last night with the balloon reading, end of Bonnie.
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428. xcool
new thunderstorm around center
Member Since: September 26, 2009 Posts: 2 Comments: 15625
PREDICT pouch synopsis


Date (UTC): 2010/07/21 11:38
Author: Boothe
Submitted at (UTC): 2010/07/21 11:49
Revised at(UTC): 2010/07/21 19:12 Pouch Name: PGI16L Official Name: Initial Center Point: 20N 88W

ECMWF: Phase Speed: -4.5 Level tracked: 700 hPa Determination: V only

Only looked at 700hPa.

GFS: Phase Speed: -5.1 Level tracked: 700 hPa Determination: V only

Only looked at 700hPa. Large quasi-stationary Southern Bay of
Campeche (SBC) circulation in the comoving frame dominates the
scene. At analysis, a sweet spot was depicted on the eastern of
a large conglomeration low, and it was reasonably close to
PGI16L. The 12 & 24-hour plots did not have PGI16L as distinct
circulation, so I interpolated. 36 hours had a PGI16L distinct
from the SBC. Then, landfall occurred.

NOGAPS: Phase Speed: -4.7 Level tracked: 700 hPa Determination: average

Examined all three levels, but none ever depicted a circulation
distinct from the SBC at any forecast time.

UKMET: Phase Speed: Level tracked: Determination:

Other potential systems:

Fairly weak 650hPa trof just came off Africa. Lots of
convection yesterday, but not as much today. May start it
tomorrow.

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As a wife as one of those men performing work on one of those relief wells, I think the safety of the men is more important than any relief efforts. Sorry that you want to put my husbands life at risk. Hind sight is 20/20. If conditions were a bit different, we could've been dealing with a hurricane with no time to evac those boys out of there. Point is, you don't risk the lives of workers who want the same thing you do, to stop this leak.
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Quoting WeatherNerdPR:

So at 8 the headline should say "BONNIE DEGENERATES TO A REMNANT LOW" , right?



try more like 11pm
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Wow...I guess she just went by my backyard...the seabreeze kicks harder than that! I wonder if we will finally see the southern side fill in now, anyone think so? Or.....is she (whisper) gone?
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i dont think they even find a circulation
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Quoting MiamiHurricanes09:
Based on surface observations and radar loops the surface circulation of Bonnie looks ill-defined. I believe that they will find TD force winds, but not a closed surface circulation.

So at 8 the headline should say "BONNIE DEGENERATES TO A REMNANT LOW" , right?
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Quoting pcbsmokey:
Pat? See that ONE little Tstorm there? Ah'think she blinked LOL!!!


Someone is Priming the Carburetor seems.

Must be tapping the Spill fuel..

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Quoting jurakantaino:
Isn't that call interaction with land?Well however you wish to describe it, "I've got a little list" of folks with whom I wouldn't be interacting.
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Speaking of preparedness. I just heard about a thing you plug into your cars lighter/accessory port and you can plug things into like a regular house plug. Think they're called converters? Anyway sounds like a neat thing to have. I'm probably the last person on the planet to know about this. :)
Member Since: August 15, 2008 Posts: 10 Comments: 3665
So far, a mostly wetter than average year for the Sahel:

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Pat? See that ONE little Tstorm there? Ah'think she blinked LOL!!!
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Quoting atmoaggie:
Yet, none of the factors, alone, means a thing. SSTs might be great (see exhibit B...onnie) but other factors nix it.

In this line of thinking, SSTs that are usually 28 C, but anomalously high by 2 C doesn't necessarily mean more activity. Everything else must come into line...a lack of shear (thanks La Nina), rain in the Sahel, a couple of good MJO pulses at the right moment, lucky placement of upper level features, etc.

Correct, that's what I was trying to say, Its a combination of things , then they are things that are still a mystery to us(humans) and probably always will be , we were never meant to know it all.
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Quoting atmosweather:
Here comes RECON!...Let's see if we have a closed circulation and any winds to TD force.
Based on surface observations and radar loops the surface circulation of Bonnie looks ill-defined. I believe that they will find TD force winds, but not a closed surface circulation.
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Here comes RECON!...Let's see if we have a closed circulation and any winds to TD force.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting BahaHurican:
What ur saying is making me think we should see some hyperactivity in the NInd and SInd later this year into next year....


I wouldn't know about "hyper"activity but yes the South Indian should see a good burst this winter relative to the rest of the southern hemisphere.
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Ouick,..get the Paddles,!,

and CLEAR !!!!


"Cha..Chunk"..

Beep,..beep,...beep..beep..





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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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