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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2111. KEEPEROFTHEGATE (Mod)
Quoting IKE:


I've seen that exact statement about 1,000 times this season.


LMAO...Mike Seidel....no wind at Dauphin Island,AL.!!!!!!!!! Sea oats dead still.
well if ya put some fans on the beach he could stand in front of them to make it look that way then we need a garden hose to spray him down to look like rain the fan will give it that driving rain look then you need a moonshine jug to blow in to give it that howling wind sound come on they can do this its easy
Member Since: July 15, 2006 Posts: 165 Comments: 52262
Quoting Asta:

Hope is not an effective plan.


Did I say it was?
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Quoting atmosweather:
And with that I need a nap LOL!

Have a good morning everyone...I'll be back this afternoon to watch the naked girl...oops I mean cyclone ;)


Haha and thanks for your "teaching"!
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And with that I need a nap LOL!

Have a good morning everyone...I'll be back this afternoon to watch the naked girl...oops I mean cyclone ;)
Member Since: September 24, 2005 Posts: 33 Comments: 9265
TropicalDepression Bonnie was^heading for a NewOrleans,Louisiana landfall in ~10hours.
(Straightline^projection using its last 2 positions. Take with HUGE grain of salt)
Copy&paste 26.4N83.4W, 26.7N84.4W, 27.0N85.1W-27.6N86.1W, 27.6N86.1W-29.7N89.7W, BIX, 22.3N74.0W, 18.5N87W, TAM, 28.7N88.4W into the GreatCircleMapper
Shortest red line denotes the movement between last two positions. Below the map shows:
TD.Bonnie had a heading of 304.1degrees (10.9degrees west of NorthWest) while traveling
a distance of 74miles(~119kilometres) over 3hours at a speed of ~25mph(~40km/h),
and was 262miles(~421kilometres) away from the coast in the direction of its heading.

^ A straightline projection does not forecast of what will happen in the future,
See blog1555post1853 for further explanation of what it does and doesn't do.
* DeepwaterHorizon is marked at 28.7N88.4W
Member Since: August 21, 2007 Posts: 0 Comments: 4860
2106. Asta
Quoting RedStickCasterette:


Do you think we will get that surge? I had read Alex put some surge/oil into LA. I hope not.

Hope is not an effective plan.
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2105. Asta
Quoting StonedCrab:
Good Morning fellow bloggers!

My guess is as long as the swirl is visible on the visible, they'll keep it as a depression.

The rigs have already been evacuated, and there is no up side to having people return yet, even with the tiniest of odds of Bonnie flaring up. It would make them appear foolish. They're in a lose-lose situation, and erring on the side of cautious is the correct call.

I agree.
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Quoting DestinJeff:


Convection starting to really POP!!!!!!


She looks to be popping up again, a little, lol.

Persistent...
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2103. tkeith
Quoting Hardcoreweather2010:
The next 2 Live shots from Mike Siedel will be recorded from Dauphin Island, AL
Take your leaf blower...
Member Since: November 1, 2004 Posts: 25 Comments: 8912
2101. IKE
Quoting DestinJeff:
Back to Page 1 of the 2010 script:

Look at this one. This one may be the one to watch as the first real start of the CV season!


I've seen that exact statement about 1,000 times this season.


LMAO...Mike Seidel....no wind at Dauphin Island,AL.!!!!!!!!! Sea oats dead still.
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The next 2 Live shots from Mike Siedel will be recorded from Dauphin Island, AL
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Quoting IKE:


That's what 30-40 knots can do to ya!
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I'd watch the Caribbean area carefully. Though I concur with the NHC about a tropical cyclone not developing in the next 48 hours, a westward moving tropical wave near the Leeward Islands will enter the basin sometime today, generating an even greater area of convection.

The 06z GFS forecasts the upper-level flow to begin to improve in around 54 hours as the upper low to the north moves into the western Gulf of Mexico. At this juncture, the wave should be in the western Caribbean Sea. I think it's possible we'll eventually see something from this, even though it's not much now.
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2095. tkeith
Quoting RedStickCasterette:


Who was that with the tunnel theory years ago? I haven't seen it in ages...
CycloneBuster...he's still around. I dont think he posts in Doc's blog anymore, but I've seen him on other blogs here.
Member Since: November 1, 2004 Posts: 25 Comments: 8912
Quoting IKE:
Cat .0000000001.......



ULL def. Bonnie - 8th Rd TKO.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
2092. IKE
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2091. tkeith
Quoting KEEPEROFTHEGATE:
i posted up link keith but to navagate the site it took me also 2 yrs to figure it out good luck
I'll probably be WU mailin ya for tips :)
Member Since: November 1, 2004 Posts: 25 Comments: 8912
2090. KEEPEROFTHEGATE (Mod)
Quoting IKE:
Cat .0000000001.......

cat no mouse1 i think
Member Since: July 15, 2006 Posts: 165 Comments: 52262
Quoting tkeith:
I hope CB dont see that...it will really mess up his tunnel theory up...


Who was that with the tunnel theory years ago? I haven't seen it in ages...
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2088. tkeith
Thanks Keeper I saved it :)
Member Since: November 1, 2004 Posts: 25 Comments: 8912
2087. KEEPEROFTHEGATE (Mod)
i posted up link keith but to navagate the site it took me also 2 yrs to figure it out good luck
Member Since: July 15, 2006 Posts: 165 Comments: 52262
2086. IKE
Cat .0000000001.......

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2085. tkeith
Quoting BadHurricane:


Yeah!!!
Americans have a new weapon for the destruction of tropical cyclones!!!
Link
I hope CB dont see that...it will really mess up his tunnel theory up...
Member Since: November 1, 2004 Posts: 25 Comments: 8912
2084. KEEPEROFTHEGATE (Mod)
Quoting tkeith:
2076. KEEPEROFTHEGATE 6:50 AM CDT on July 24, 2010

is that Plymoth site a pay site Keeper?

could you link it for me?


Link
Member Since: July 15, 2006 Posts: 165 Comments: 52262
Quoting WeatherNerdPR:

It would be interesting if she were to blow convection and organize it, as well as drop pressures and up those winds, but that's highly improbable.


Not with 30 knots of confluent upper flow and virtually no moisture left.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting tkeith:
2076. KEEPEROFTHEGATE 6:50 AM CDT on July 24, 2010

is that Plymoth site a pay site Keeper?

could you link it for me?


Link
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Quoting Hardcoreweather2010:


Yeah!!!
Americans have a new weapon for the destruction of tropical cyclones!!!
Link
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Quoting P451:
12HR WV Loop



So, my fiance/hubby/whatever should be getting whacked at work right now, or starting to, by Bonnie's naked swirl in Pascagoula?

I just warned him to look out, lol.
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2079. tkeith
2076. KEEPEROFTHEGATE 6:50 AM CDT on July 24, 2010

is that Plymoth site a pay site Keeper?

could you link it for me?
Member Since: November 1, 2004 Posts: 25 Comments: 8912
Quoting IKE:
You can see the bare-naked swirl now....


It would be interesting if she were to blow convection and organize it, as well as drop pressures and up those winds, but that's highly improbable.
Member Since: July 7, 2010 Posts: 0 Comments: 5521
Quoting WeatherNerdPR:
Good Morning. I see the NHC doesn't wanna let Bonnie go. Why can't they just end this?!


They will likely be at 11AM...

...BONNIE COULD DEGENERATE INTO AN AREA OF LOW PRESSURE...WARNINGS WILL LIKELY BE DISCONTINUED LATER THIS MORNING...
Member Since: September 24, 2005 Posts: 33 Comments: 9265
2076. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 165 Comments: 52262
Quoting DestinJeff:
Can't find Geraldo in Dennis either.

Then, maybe that's a good thing.


Hmm maybe I should make it a quest to find it!
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Good Morning. I see the NHC doesn't wanna let Bonnie go. Why can't they just end this?!
Member Since: July 7, 2010 Posts: 0 Comments: 5521
Quoting IKE:
You can see the bare-naked swirl now....


oh Bonnie, put some clothes on
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Quoting DestinJeff:
Can't find Geraldo in Dennis either.

Then, maybe that's a good thing.


Ya think they were that embarrassed of it? lol it truly was something.
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I think is time to look elsewhere and search for any candidate that may turn into Colin. But as I see things evolving, it may take the next couple of weeks to get Colin as the MJO is not favorable.
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Quoting IKE:
You can see the bare-naked swirl now....



Well she is cute! From Walmart to naked swirl, lol.
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Let me see if I can find somebody else to do it :) We will be lucky if we get any waterspouts today. We do need the rain down here cause my grass is brown after only 1 little shower in the entire month of July
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2066. IKE
You can see the bare-naked swirl now....

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Quoting DestinJeff:
Here is some classic Geraldo:


e>
Quoting DestinJeff:
Here is some classic Geraldo:

Quoting DestinJeff:
You must do the Mime in Strong Wind thing in the live shot!


ugh cannot find the Dennis shots with Geraldo.
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Quoting atmosweather:


I'm almost begging ya to...LOL!


Beg him, lol...
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Quoting Hardcoreweather2010:
Not goi
Not going to do that cause I want to be able to sell TWC video footage like I have in the past :)


K. Just sounded funny...
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About JeffMasters

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