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 tkeith:
If you turn out to be right...you'll be my new best friend



that was a joke right your kinding right
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Quoting connie1976:



what does that mean?

That means we can all enjoy a nice time at the beach for a couple of weeks. :-)
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Quoting fallinstorms:


yes

alex will be the only hurricane
If you turn out to be right...you'll be my new best friend
Member Since: November 1, 2004 Posts: 25 Comments: 8937
even experts are agreeing

this season is poof
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i made 500+ commets this for a weak TS Bonnie

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Quoting Thundercloud01221991:



does this include Hurricane Alex?


yes

alex will be the only hurricane
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Quoting jasoniscoolman2010x:
next wave to watch.



and it will go POOF this like the rest
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Quoting cirrocumulus:
Is it just me, or does it look like development starting again around the Dominican Republic. Since Bonnie is gone, the waters are going to warm rapidly again. She didn't even cause clouds or flooding.


The showers and storms are being generated from the upper divergence across the area and not anything at the surface. There is an upper level feature with good mid level and upper level energy N of Hispanola that could eventually run into better environmental conditions in a couple of days. It's something to watch.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
next wave to watch.
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Quoting Orcasystems:


I do that with the good beer also... hides them from the company :)
I'd like to visit Canada...but I heard they dont sell Landshark Lager there though :)
Member Since: November 1, 2004 Posts: 25 Comments: 8937
Quoting tkeith:
122. fallinstorms

i know im 100% right

now where have I heard that before?


lol
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Quoting IKE:
Found this from this mornings San Juan discussion and I got hammered on here the other day for posting the MJO maps...

"ASIDE FROM TS BONNIE NEAR THE BAHAMAS...TROP ATLC VERY QUIET AND
MJO PROGNOSIS CONTINUE TO SUGGEST A STRONG DOWNWARD PHASE ACROSS
THE WRN HEMISPHERE OVR THE NEXT TWO WEEKS POSSIBLY LASTING
THROUGH THE THIRD WEEK OF AUGUST AS MJO SIGNAL CONTINUES TO
PROPAGATE INTO THE MARITIME CONTINENT/WRN PACIFIC."




what does that mean?
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How did everyone's shower curtains hold up?
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-_-
Member Since: November 1, 2004 Posts: 25 Comments: 8937
Quoting tkeith:
as a matter of fact I do have a few Mooseheads in the fridge :)

I have to admit they are at the back though...


I do that with the good beer also... hides them from the company :)
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Quoting Tazmanian:



lol

:D
Member Since: July 7, 2010 Posts: 0 Comments: 5725
144. xcool
www.wxresearch.com/

call for 8 named
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look at this wave.
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ike just loves thsoe downward mjo forecasts, doesn't he? sadly for him, not one of them have yet to pan out since the season begun, ha
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Quoting StormW:


I like you...u funny!


Evening Storm!
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Quoting StormW:


I like you...u funny!


I have to agree. Kids go back to school please.
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Quoting StormW:


I like you...u funny!
me too...
Member Since: November 1, 2004 Posts: 25 Comments: 8937
Next update
I'll have an update Saturday morning.



no need dr m go take a nic weekend off am giveing you a vacanin
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Quoting WeatherNerdPR:

I never knew "worng" was a word. lol



lol
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Quoting centex:
You want to be put on ignore?




i see no one can take jokes
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Quoting Tazmanian:



your 100% worng lol

I never knew "worng" was a word. lol
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting Tazmanian:
am forcasting 100 name storms this year
You want to be put on ignore?
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122. fallinstorms

i know im 100% right

now where have I heard that before?
Member Since: November 1, 2004 Posts: 25 Comments: 8937
I could go for a Kokanee, but Labatts is more my taste. I miss that, but honestly I would rather have a huge bag of Smarties!! Glad that Bonnie is weaker now. I know strong storms are fun to track, but none of us on the gulf coast (or anywhere for that matter) need one on the doorstep!
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Is it just me, or does it look like development starting again around the Dominican Republic. Since Bonnie is gone, the waters are going to warm rapidly again. She didn't even cause clouds or flooding.
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Quoting Levi32:


Well, in my opinion, we're more likely to get those numbers for the month of September by itself lol.



yup
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Quoting fallinstorms:
rip bonnie

NEXT!

this season has been so overhyped

6 name storms
1 hurricane

is my prediction



does this include Hurricane Alex?
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Quoting fallinstorms:


i know im 100% right

conditions are too horrible for any storm this year

we even be lucky to get to number 6!



your 100% worng lol
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Quoting fallinstorms:
rip bonnie

NEXT!

this season has been so overhyped

6 name storms
1 hurricane

is my prediction


Well, in my opinion, we're more likely to get those numbers for the month of September by itself lol.
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am forcasting 100 name storms this year
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Quoting Orcasystems:


Hmm that sort of sounds Canadian....
Do you have any Moosehead of Kokanee?
as a matter of fact I do have a few Mooseheads in the fridge :)

I have to admit they are at the back though...
Member Since: November 1, 2004 Posts: 25 Comments: 8937
Quoting atmosweather:


Good luck with that.


i know im 100% right

conditions are too horrible for any storm this year

we even be lucky to get to number 6!
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Quoting fallinstorms:
rip bonnie

NEXT!

this season has been so overhyped

6 name storms
1 hurricane

is my prediction




a overhyped caster
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bonnie should not of been name

but i guess they gotta make it look active
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6 name storms
1 hurricane

is my prediction


That's a liitle conservative for..August
Member Since: November 1, 2004 Posts: 25 Comments: 8937
Clyde ULL starting to move N. Whatever that means?
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this TD is RIP
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Quoting fallinstorms:
rip bonnie

NEXT!

this season has been so overhyped

6 name storms
1 hurricane

is my prediction


Good luck with that.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting tkeith:
Not much happening... yet... hmmm where are all of the NOLA panic casters?

we're out puttin our shutters up...between beers.


Hmm that sort of sounds Canadian....
Do you have any Moosehead of Kokanee?
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bonnie won't even be a rain shower for new orleans
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113. xcool
fallinstorms .wow
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rip bonnie

NEXT!

this season has been so overhyped

6 name storms
1 hurricane

is my prediction
Member Since: Posts: Comments:
111. xcool
lmao
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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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