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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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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1460. GBguy88
Quoting cntrclckwiseSpenn:


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


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.
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Quoting Levi32:


Well, my point is they flew right over the peninsula, and they were on a mission :) Must have been a sight to see for anyone watching. Would be pretty cool to watch one heading towards the storm.
It was. At the time the center was 50, maybe 100 miles away, but it was headed in that direction. Been living in the same place for 25 years and never saw or heard a similar plane at that low an altitude flying in that direction at that time of day. Of course I can't be sure, but I think that it was the HH.
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Quoting cntrclckwiseSpenn:


wow, you've had some major bad luck with weather. You were there then for the orlando tornado outbreak? I think that was in Feb...


Unfortunately yes...February 23rd 1998...there have been a couple more since then, most notably on November 7th 2006 when I saw one rip through the neighborhood next to ours.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
1457. beell
Ugly Water Vapor Loop

g'nite.
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Bonnie loves the warm water tonight!

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Quoting CybrTeddy:
Interesting to note, a lot of major cities on the coast line have been hit by a hurricane since 1921 except Tampa. Ike hit Houston, Katrina hit New Orleans, Andrew hit Miami, Hugo hit Charleston, New York by Gloria.


Galveston used to be a major city until it was hit by a hurricane....
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1454. Levi32
Quoting HaboobsRsweet:

I guess...C-130s are fat and slow, see them fly everyday. Nothing special. And they were not in the storm and my point was when they are in a storm they can not.


Well I've never seen a C-130 in Alaska lol.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
Quoting cirrocumulus:
Tampa is definitely in the cone of possibility much more so in a sense than even 50 miles farther north.


I would think more storms would hit our area due to recurving, but they seem to head to Destin/Ft. Walton beach....
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RECON heading towards the COC from the NE.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting atmosweather:


Orlando...moved there from Kendall, FL on August 25th 1992...I'm sure you can guess why =(


wow, you've had some major bad luck with weather. You were there then for the orlando tornado outbreak? I think that was in Feb...
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Quoting Levi32:


Well, my point is they flew right over the peninsula, and they were on a mission :) Must have been a sight to see for anyone watching. Would be pretty cool to watch one heading towards the storm.

I guess...C-130s are fat and slow, see them fly everyday. Nothing special. And they were not in the storm and my point was when they are in a storm they can not.
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Tampa is definitely in the cone of possibility much more so in a sense than even 50 miles farther north.
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Quoting CybrTeddy:
Tampa Bay is seriously overdue for a hurricane to hit.. and when one does I fear many will be caught off guard. This was the last storm to do so in 1921.



yeah, it was 1921....and actually the storm might of been one of the strongest of all-time to hit the US mainland.
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Quoting cntrclckwiseSpenn:


wow, I've barely had any tropical storms come our way here let alone hurricanes. The worst weve had is the no name storm in 1993, TS Marco, Jeanne (I think). Charley was sort of like bonnie today, it was practically a normal day because of the lack of size.

what part of FL are you in?


Orlando...moved there from Kendall, FL on August 25th 1992...I'm sure you can guess why =(
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting hurrkat05:
THE ULL THAT WAS AFFECTING BONNIE HAS NOW MOVED FOR AWAY AND BONNIE...ITS STARTING TO SLOWLY CREATE A NEW ATMOSPHERE AROUND HER...CONVECTION HAS STARTED TO FIRE AROUND THE CENTER AND BY 11AM BONNIE WILL BE ONCE AGAIN A TROPICAL STORM..THE PRESSURES ARE FALLING SLOWLY AND BONNIE STILL HAS THE WARM GULF STREAM TO CROSS OVER...ALL INTERESTS ALONG THE LA AND MISS COASTS SHOULD BE PREPARED TO TAKE QUICK ACTION IF TROPICAL STORM WARNINGS OR REPLACED BY HURRICANE WARNINGS...THIS REMAINS A DANGEROUS SITUATION AND BONNIE IS LIKELY TO SLOW DOWN EVEN MORE IN THE NEXT ADVISORY...THE DRY AIR IS CURRENTLY NOT AFFECTING BONNIE AND BANDING IS STARTING TO DEVELOP OVER BONNIE...ILL BE BACK AT 5AM UNLESS CONDITIONS RAPIDLY CHANGE...



huh another wacko
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1445. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Interesting to note, a lot of major cities on the coast line have been hit by a hurricane since 1921 except Tampa. Ike hit Houston, Katrina hit New Orleans, Andrew hit Miami, Hugo hit Charleston, New York by Gloria.
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It's ironic how TD3 starts building convection on the west side where it is supposed to die out. That's what 30 degree water does.
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1442. angiest
Last night or the night before someone asked about tropical storms that went there immediately without being a depression first. I mentioned Hurricane Claudette from 2003. Here is an excerpt from the Wikipedia entry that matches my own recollection from watching the wave that spawned the hurricane as it chugged through the Caribbean.

A tropical wave moved off the coast of Africa on July 1. It steadily organized as it moved westward, and resembled a tropical depression by July 7. However, surface reports and reconnaissance aircraft indicated the system did not have tropical characteristics, and remained simply a low-pressure system. The wave produced tropical storm-force winds as it moved through the Lesser Antilles on July 8, but did not acquire tropical characteristics until it reached the eastern Caribbean. Because it had tropical storm-force winds, the system was upgraded immediately to Tropical Storm Claudette after it developed a low-level circulation later on July 8.[1]
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1441. Levi32
Quoting HaboobsRsweet:

They werent in the core of the storm yet so sure I guess maybe you saw them...my point was they are no different than a normal C-130 so saying they sound and look different is false. Based on your post they were not in the system yet...just a weak feeder band if you even want to call it that.


Well, my point is they flew right over the peninsula, and they were on a mission :) Must have been a sight to see for anyone watching. Would be pretty cool to watch one heading towards the storm.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
Quoting angiest:


I don't know if you are correct, but that is the same thought I had. And even if they flew through a storm over land they couldn't really drop probes.

The sondes arent the issue...we do the same thing from the ground all the time for upper air data. They are lauched with ballons and when they pop or air runs out the devices freefall and hey maybe you get one in the backyard...hence the parachute.
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Quoting angiest:


"Indian lore" also held that Waco, TX was immune to strong tornadoes. A belief held until an estimated F5 obliterated much of downtown in 1953, currently tied as the 10th deadliest tornado in US history and tied for first in Texas history. Several other cities had similar bits of "Indian lore" that were blown away quite literally.


LOL, I take it with a grain of salt...but it just shows the ignorance of my area for a major hurricane. We are due for one, just like Cali is for a big quake.
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gorgea never get hit
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THE ULL THAT WAS AFFECTING BONNIE HAS NOW MOVED FOR AWAY AND BONNIE...ITS STARTING TO SLOWLY CREATE A NEW ATMOSPHERE AROUND HER...CONVECTION HAS STARTED TO FIRE AROUND THE CENTER AND BY 11AM BONNIE WILL BE ONCE AGAIN A TROPICAL STORM..THE PRESSURES ARE FALLING SLOWLY AND BONNIE STILL HAS THE WARM GULF STREAM TO CROSS OVER...ALL INTERESTS ALONG THE LA AND MISS COASTS SHOULD BE PREPARED TO TAKE QUICK ACTION IF TROPICAL STORM WARNINGS OR REPLACED BY HURRICANE WARNINGS...THIS REMAINS A DANGEROUS SITUATION AND BONNIE IS LIKELY TO SLOW DOWN EVEN MORE IN THE NEXT ADVISORY...THE DRY AIR IS CURRENTLY NOT AFFECTING BONNIE AND BANDING IS STARTING TO DEVELOP OVER BONNIE...ILL BE BACK AT 5AM UNLESS CONDITIONS RAPIDLY CHANGE...
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Quoting Levi32:


See 1429.

They werent in the core of the storm yet so sure I guess maybe you saw them...my point was they are no different than a normal C-130 so saying they sound and look different is false. Based on your post they were not in the system yet...just a weak feeder band if you even want to call it that.
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Quoting atmosweather:


It only needed probably an hour or two longer and it would have been a Category 5. It was already 150 mph at landfall...small but extremely intense central core, zero wind shear, much more instability in the atmosphere compared to normal (the abnormal southerly trough helped with that). That was a monster. Got sustained 85 mph winds here at my house and 2 gusts to 109 mph.


wow, I've barely had any tropical storms come our way here let alone hurricanes. The worst weve had is the no name storm in 1993, TS Marco, Jeanne (I think). Charley was sort of like bonnie today, it was practically a normal day because of the lack of size.

what part of FL are you in?
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1434. angiest
Quoting HaboobsRsweet:

When they are in a storm it is because of the risk of crashing over land...too dangerous.


I don't know if you are correct, but that is the same thought I had. And even if they flew through a storm over land they couldn't really drop probes.
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Holy smokes! TD3 loves that warm water at 30 degrees. It keeps increasing every several minutes on NASA.

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1432. angiest
Quoting wfyweather:


takes a strong trough to do that... and... that means it has to be timed perfectly... which is why it doesnt happen often


My point. :)
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1431. Levi32
Quoting HaboobsRsweet:

Yes they could if not in a storm...


See 1429.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
Im out guys... wish me luck with my intercept tomorrow
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1429. Levi32
Quoting HaboobsRsweet:

When they are on a mission they do not...it is illegal. Google earth could have misplaced the point or they could have been riding right on the coastline.
Quoting Levi32:



No they came from Louisiana and went right over the peninsula. No way it was a mistake. I wish I had screenied it at the time but I can't get an archive of it. It's US airspace they can easily request permission for such situations.



Here here here.....I got it.

Member Since: November 24, 2005 Posts: 635 Comments: 26684
Quoting HaboobsRsweet:

When they are in a storm it is because of the risk of crashing over land...too dangerous.


Guess it makes since considering they fly so low
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Quoting Levi32:


No they came from Louisiana and went right over the peninsula. No way it was a mistake. I wish I had screenied it at the time but I can't get an archive of it. It's US airspace they can easily request permission for such situations.

Yes they could if not in a storm...
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1426. angiest
Quoting cntrclckwiseSpenn:


Ive heard of local lore that the Indians that lived in my Florida county (Manatee) even believed that it was not prone to landfalling hurricanes.


"Indian lore" also held that Waco, TX was immune to strong tornadoes. A belief held until an estimated F5 obliterated much of downtown in 1953, currently tied as the 10th deadliest tornado in US history and tied for first in Texas history. Several other cities had similar bits of "Indian lore" that were blown away quite literally.
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Quoting wfyweather:


Illegal... why in the living heck would it be illegal?

When they are in a storm it is because of the risk of crashing over land...too dangerous.
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Tampa Bay is seriously overdue for a hurricane to hit.. and when one does I fear many will be caught off guard. This was the last storm to do so in 1921.

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Quoting angiest:


By recurving storms I meant, in part, storms that were further south in the Caribbean that turned north and came in like Charley did. Storms moving west to east in the Gulf appear rather rare.


It depends on the time of season....as far as historical tracks. I think July is a period where forecasters watch the GOM, with the tracks going west to east.
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Station 42040
NDBC
Location: 29.212N 88.207W
Conditions as of:
Sat, 24 Jul 2010 03:50:00 UTC
Winds: NNE (20°) at 7.8 kt gusting to 7.8 kt
Significant Wave Height: 2.3 ft
Dominant

Closest buoy to oil spill site...no prob...yet
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1421. scott39
Quoting cirrocumulus:
Say it ain't so Joe! TD3 is getting stronger again.

Thats a pulse! Lets see if it lasts!
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1420. Levi32
Quoting HaboobsRsweet:

When they are on a mission they do not...it is illegal. Google earth could have misplaced the point or they could have been riding right on the coastline.


No they came from Louisiana and went right over the peninsula. No way it was a mistake. I wish I had screenied it at the time but I can't get an archive of it. It's US airspace they can easily request permission for such situations.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
Quoting HaboobsRsweet:

When they are on a mission they do not...it is illegal. Google earth could have misplaced the point or they could have been riding right on the coastline.


Illegal... why in the living heck would it be illegal?
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Anyone have current steering map for Bonnie?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting angiest:


By recurving storms I meant, in part, storms that were further south in the Caribbean that turned north and came in like Charley did. Storms moving west to east in the Gulf appear rather rare.


takes a strong trough to do that... and... that means it has to be timed perfectly... which is why it doesnt happen often
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Quoting Levi32:


They did earlier....could see it on Google Earth. They will fly over land when necessary. They weren't about to go all the way around the Florida Peninsula this morning just to get to Bonnie.

When they are on a mission they do not...it is illegal. Google earth could have misplaced the point or they could have been riding right on the coastline.
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Quoting atmosweather:


A lot of it is just pure luck...and also the shape of the peninsula...most storms that come from the S will either turn NE into extreme SW FL (Wilma/Charley) or just move N-ward into the panhandle. You need a strong fall-like trough to catch it at just the right time.


Ive heard of local lore that the Indians that lived in my Florida county (Manatee) even believed that it was not prone to landfalling hurricanes.
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Angiest: It shows what one degree Celsius can do. It may be crossing a narrow band of 30 degree water, but it will still be 29 in a little while. That should be interesting!
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1413. GBguy88
If Bonnie makes a comeback, someone'll have to break down and throw a big crow feast for the blog. Most of it, anyhow ;)
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yeah its wrapping convection around the center and most likely if it keeps this up... strengthening some... See... this shows my point... Everyone that called it open and said it was dead called it too soon. exactly what ive been saying all night.
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1411. angiest
Quoting cntrclckwiseSpenn:


well there are a number of storms that have gone upto the panhandle, or have hit towards ft myers as well though. Not all storms move east to west...some cane start-out in the SW carib or GOM.


By recurving storms I meant, in part, storms that were further south in the Caribbean that turned north and came in like Charley did. Storms moving west to east in the Gulf appear rather rare.
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.