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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R.I.P. Tropical Storm Bonnie.

She gave much needed rain to Florida.
Member Since: August 9, 2009 Posts: 10 Comments: 5026
959. xcool
find 43 FL wow
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Night Chief..
Member Since: July 3, 2005 Posts: 426 Comments: 128764
Quoting stormpetrol:
Quoting Patrap:
The Mayans are not Happy with BP atall.

Were DOOMED

My wife is of Mayan ancestry, just click on my new avatar, true but the Mayans were supersmart!

pat you're a good man though , hope all well goes well in NOLA, even though Bonnie might appear like a small insignificant system, it can reek havoc.


Thanx..


We're going to the Antiques Road Show in Miss,Biloxi, in the am.

Hopefully.

The Mayan were and are a Great People.
Member Since: July 3, 2005 Posts: 426 Comments: 128764
Quoting StormW:
Good night all!


G'night Storm!
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting FLdewey:
The death of Bonnie is kind of like Michael Jackson.

Some hardcore fans think he's still alive.

Huh... maybe Bonnie faked her own death... she might pop up as a squall on Lake Winnipeg.


Hey! Been a lurker since 2005 and this is my first post. I've very much enjoyed learning about tropical systems, tracking storms and getting to know some terminology.

I grew up sailing on Lake Winnipeg (short seasons...grr) and now keep a boat down in the St. Pete Beach area and although we summer up here, I keep a very watchful eye (some might say obsessive) on any tropical activity.

I liked the M. Jackson comment...just wondering if you've had any direct experience with Lake Winnipeg.

btw, Storm's, Levi's and a number more post excellent commentary. Learning lots!

Best regards.
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living here in Houston BP was known for absolutly the worst safety at refinery and everywhere else...just no accountability they made so much money the fines for the 100's of violations were nothing to them they just payed their way out of everything now look at this mess...the moritorium on drilling is now costing more jobs here on the gulf cost. What a total total disaster. I hope bonnie makes little impact on the oil. Bye bye bonnie
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Quoting stormpetrol:

Very true and thanks,We went to Belize the last week of May this year and I must say I really enjoyed myself , also went to Chetumal, MX, as of Sept 7, we will have been married 25 years and that is first time I been to her country, about time don't you think:), Next year hopefully I will return to my ole stomping ground and visit Atlantis On PI my son is itching to go, plus we have family there we want to visit with anyway.
If u make it let me know. I'll stand u lunch at one of those cool restaurants they have over there... Mosaic is the latest one I've been to.
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Good Evening. Garcia did a nice job with the 8 p.m. Discussion tonight.

(Excerpt)
THE CARIBBEAN SEA...
SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE TO LINGER OVER THE NORTHERN CARIBBEAN AND INLAND PORTIONS OF THE GREATER ANTILLES NORTH OF 14N BETWEEN 64W AND 80W.
THIS GROUP OF ISLANDS HAVE ALREADY RECEIVED CONSIDERABLE AMOUNTS OF RAINFALL FROM WHAT IS NOW TROPICAL DEPRESSION BONNIE. THE CONTINUATION OF RAINFALL ACROSS THESE AREAS INCREASES THE THREAT OF FLOODING AND POTENTIAL MUDSLIDES IN AREAS OF HIGH SATURATED TERRAIN.

BROAD CYCLONIC CIRCULATION ALOFT AROUND AN UPPER LEVEL LOW SPINNING NORTH OF THE CARIBBEAN SEA NEAR 20N68W IS PRODUCING ALL THIS WEATHER OVER THIS REGION.
DRY AIR INTRUSION FROM THE NORTH CENTRAL ATLANTIC IS FURTHER MAINTAINING THE UPPER LOW AND ENHANCING THE CONVECTION GENERATED BY IT.
EXPECT SHOWERS AND THUNDERSTORMS TO CONTINUE OVER THE MENTIONED AREA AS THE UPPER LEVEL LOW MOVES SW TOWARDS THE SE BAHAMAS.
A TROPICAL WAVE IS JUST EAST OF THE LESSER ANTILLES GENERATING ISOLATED SHOWERS AND POSSIBLE THUNDERSTORMS OVER THE FAR EASTERN CARIBBEAN EAST OF 63W.
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Quoting atmosweather:


And even those were 2+ hours ago.
Yep.
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Here is a good tropical resource site I found.

Tropical Atlantic
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I'm out. See y'all (not Bonnie) tomorrow morning.
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Quoting cloudy0day:


The vent window was the air conditioner on my first car, lol.


Yep -- now all cars have ac - no more vents
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Quoting MiamiHurricanes09:
The closest we found to W winds were SW winds. No more TD at 11 P.M EDT.


And even those were 2+ hours ago.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting jeffs713:

Look at the depth... all 500+ km down.
Meaning?
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Quoting StormW:
Good night all!
Good night senior chief! -_-, LOL!
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Quoting Skyepony:
I like the NHC track. Maybe still a little to the right~ Mississippi coast or near the LA/MS border. Some circulation is together, looks like it going to do what it can in these conditions, dealing with the forward speed & 20+ kts shear, shouldn't be too much to deal with other than oil. Even then~ small, quick, weak storm...surge doesn't look the least bit extreme.

MM5E is out preforming the other models with a 28nm average error today. OFCL is the best of the rest with 62. Here's the MM5E forecast for surge. Dark Blue is less than 1m.
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Quoting StormW:


I know, I was just messin around with ya. I still believe, based on the still present signals in the ocean and atmosphere, that we will see some of the lower end of the predicted numbers (i.e. CSU 18...etc. I don't believe 20+). I'm still at 17-19. I could go on and on with the reasons why, but I'm getting ready to sign off. Maybe I'll do that tomorrow...make a side by side comparison of the pluses and negatives.


Oh i know you were messing. That would be very interesting to read thought. You have a goodnight and I will be looking forward to coming back here to read more of what yall have to say.
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941. Skyepony (Mod)
I like the NHC track. Maybe still a little to the right~ Mississippi coast or near the LA/MS border. Some circulation is together, looks like it going to do what it can in these conditions, dealing with the forward speed & 20+ kts shear, shouldn't be too much to deal with other than oil. Even then~ small, quick, weak storm...surge doesn't look the least bit extreme.

MM5E is out preforming the other models with a 28nm average error today. OFCL is the best of the rest with 62. Here's the MM5E forecast for surge. Dark Blue is less than 1m.
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Quoting Ldog74:
Given the size of Bonnie, were quite lucky that shes not going to suddenly find herself in a highly conducive environment for strengthening...a Cyclone Tracy part II would be less than welcome.

Storm and atmo, I have the distinct pleasure of owning a 66 mustang, at the age of 18. Not all of us youngsters are naive to the old days of automobile transportation.

Well, cool. Not that old myself.

But I drove a 61 Fairlane to high school. And I still tinker...
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Quoting scottc42:
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.

If Big Oil could do whatever it wanted, it would drilling in the middle of nowhere Alaska instead of being forced out into the middle of the gulf. A spill in Alaska would only affect a few caribou, rather than millions of people's livelihoods.
Another 4 years of them going on the way they have been, and they would have been up there drilling... remember drill baby drill? I'm glad they didn't get a chance to do any more than they did, because they would have continued to carry these careless practices around the world, polluting and destroying the natural environments of people who, unlike the average American citizen, have little hope of having their rights preserved.
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Quoting atmosweather:
Nothing at all in the way of a closed LLC. We're down to a remnant wave.
The closest we found to W winds were SW winds. No more TD at 11 P.M EDT.
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Quoting atmoaggie:
Forehead, meet palm. Palm, forehead. lol.



lololol i toted a cursing
Member Since: July 18, 2009 Posts: 1 Comments: 994
No west winds; look for Bonnie to lose here tropical depression status at 11 P.M EDT.

000
URNT15 KNHC 240145
AF305 0603A BONNIE HDOB 26 20100724
013530 2613N 08301W 9248 00784 0107 +227 //// 158007 008 016 000 05
013600 2613N 08303W 9248 00782 0106 +229 +226 085002 003 015 000 03
013630 2613N 08305W 9255 00777 0106 +230 +225 048003 004 /// /// 03
013700 2613N 08305W 9255 00777 0106 +232 +225 089004 004 017 000 03
013730 2616N 08305W 9252 00782 0109 +229 +227 072006 007 016 001 00
013800 2617N 08305W 9248 00786 0109 +227 //// 065007 008 016 000 01
013830 2619N 08305W 9247 00786 0110 +225 //// 074009 011 018 000 01
013900 2620N 08305W 9245 00788 0110 +224 //// 080011 012 018 000 01
013930 2622N 08305W 9249 00782 0109 +225 //// 090012 013 018 000 01
014000 2624N 08306W 9248 00784 0107 +226 //// 086015 017 022 000 01
014030 2625N 08306W 9252 00777 0106 +228 +227 088020 022 025 000 00
014100 2627N 08307W 9250 00781 0108 +224 //// 089027 030 032 001 01
014130 2628N 08307W 9250 00784 0111 +219 //// 091034 038 036 002 01
014200 2630N 08308W 9242 00793 0115 +216 //// 096037 038 036 000 01
014230 2631N 08308W 9246 00792 0118 +216 //// 094040 042 036 000 05
014300 2633N 08309W 9251 00790 0121 +216 //// 094042 043 034 001 01
014330 2635N 08309W 9254 00790 0123 +216 //// 090039 041 034 002 01
014400 2636N 08309W 9250 00794 0126 +211 //// 091038 038 033 004 01
014430 2638N 08310W 9247 00797 0127 +213 //// 095039 039 033 002 01
014500 2639N 08310W 9248 00799 0128 +215 //// 092040 042 034 001 01
$$
;
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Quoting BahaHurican:
Is this where we burst into tears and flood out our keyboards?

Anyway there's more Twaves in the MDR where Bonnie came from....


Well...... it is so bad..... I couldn't find enough left of Bonnie to draw a single squiggly line! LOL
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Quoting will45:


lol sorry for off topic but my wife was pushing my car with another car from behind. She pushed me about 5 miles before i realized i didnt have the ignition switch turned on lmao.
Forehead, meet palm. Palm, forehead. lol.
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Quoting BahaHurican:
I did think she had that look, and being from Belize I was kinda thinking so w/out saying anything... that's actually kinda cool... I keep thinking what kind of cool info was lost when the Spaniards destroyed the books / libraries in the Central and South American empires they overthrew...

Very true and thanks,We went to Belize the last week of May this year and I must say I really enjoyed myself , also went to Chetumal, MX, as of Sept 7, we will have been married 25 years and that is first time I been to her country, about time don't you think:), Next year hopefully I will return to my ole stomping ground and visit Atlantis On PI my son is itching to go, plus we have family there we want to visit with anyway.
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Someday soon, we'll be reminiscing about rear wheel drive...
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Quoting F4PHANTOM:
Leaded gas


yea, and gas was just 20 cents a gallon!
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Nothing at all in the way of a closed LLC. We're down to a remnant wave.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting F4PHANTOM:
Didn't need a starter if you could push if fast enough and pop the clutch while in 1st gear


lol sorry for off topic but my wife was pushing my car with another car from behind. She pushed me about 5 miles before i realized i didnt have the ignition switch turned on lmao.
Member Since: July 18, 2009 Posts: 1 Comments: 994
Quoting F4PHANTOM:
Leaded gas
And hood latch, well, under the hood. No in-car lever.
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You can't forget the bright light switch on the floor lol & the hood latch opens by needle nose pliers or from under the hood lol..
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Given the size of Bonnie, were quite lucky that shes not going to suddenly find herself in a highly conducive environment for strengthening...a Cyclone Tracy part II would be less than welcome.

Storm and atmo, I have the distinct pleasure of owning a 66 mustang, at the age of 18. Not all of us youngsters are naive to the old days of automobile transportation.

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Quoting beell:
Maybe not quite the best modeled upper level environment I have seen for develpment.
Pretty respectable upper level pressure gradient up top-between the H and the ULL's.

GFS 18Z 200mb/Valid 06Z Saturday.

Photobucket
Link


That gradient of SE-erly upper winds is what is going to prevent Bonnie from vertically stacking and remaining a tropical cyclone.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting thelmores:
Look, lets face reality....... look at all the dry air...... look at the 25mph shear, look at the position of Bonnie in relation to the ULL.....

I know some of you have established a relationship with Bonnie, and her existence...... but let me explain..... Bonnie is still breathing....... but she is brain dead! Bonnie will never exist as you remembered her! LOL

Sorry for the poor analogy...... but I was trying to evoke an emotional response...... Bonnie is for all practical purposes history......
Is this where we burst into tears and flood out our keyboards?

Anyway there's more Twaves in the MDR where Bonnie came from....
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Quoting StormW:


Yep.

Do ya remember, no seatbelts?
Yep. Do you remember, no child safety seats? I rode across this country to San Diego in a playpen in the back of a van when I was a year old. Sounds nuts, but was normal then.
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Not a trick question Storm W. Just amazing year in and year out it is going to be 7 hurricanes 3 major or 17 tropical storms and you might see 2 hurricanes and 6 tropical storms. Not complaining at all just people start to get on the edge about a tropical storm (well now depression). My wife works for a Diabetic doctor and 15 patients canceled because of the rain we might get in New Orleans. LOL. I value your opinion have for 3 years by reading your post. Your very intelegent when it comes to the weather and have been 75% right last year. Thank you.
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Quoting Ossqss:
Wow, off topic, but did ya see this?

2 hours ago 7.4 Moro Gulf, Mindanao, Philippines Map
2 hours ago 7.6 Moro Gulf, Mindanao, Philippines Map
3 hours ago 7.3 Moro Gulf, Mindanao, Philippines Map

http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/quakes_all.php

Look at the depth... all 500+ km down.
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Quoting stormpetrol:

My wife is of Mayan ancestry, just click on my new avatar, true but the Mayans were supersmart!
I did think she had that look, and being from Belize I was kinda thinking so w/out saying anything... that's actually kinda cool... I keep thinking what kind of cool info was lost when the Spaniards destroyed the books / libraries in the Central and South American empires they overthrew...
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Quoting StormW:
The ONLY way Bonnie could attempt any type of "comeback" is if she can fight off the dry air.

There are 2 very short windows, and very small area where the wind shear, as far as speed, relaxes. That's about 5 hours from now, and at 30-36 hours in the forecast period






Hey StormW - - there is more moist air coming up from Cuba... Could this help moisten Bonnie up? Before, there was just Dru air in that location...
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912. beell
Maybe not quite the best modeled upper level environment I have seen for development.
Pretty respectable upper level pressure gradient up top-between the H and the ULL's.

GFS 18Z 200mb/Valid 06Z Saturday.

Photobucket
Link
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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.

If Big Oil could do whatever it wanted, it would drilling in the middle of nowhere Alaska instead of being forced out into the middle of the gulf. A spill in Alaska would only affect a few caribou, rather than millions of people's livelihoods.
Member Since: Posts: Comments:

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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.