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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NHC doesn't want to let Bonnie go yet.

...CENTER OF BONNIE EMERGES INTO THE EASTERN GULF OF MEXICO...


SUMMARY OF 800 PM EDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...26.4N 82.5W
ABOUT 445 MI...715 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 45 MI...75 KM WNW OF FT. MYERS FLORIDA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/HR
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 17 MPH...27 KM/HR
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES

Member Since: Posts: Comments:
Quoting hurrkat05:
PATRAP SOONER OR LATER THEY WILLGET THE PICTURE BONNIE WILL SURPRISE LOTS IN HERE...BONNIE IS GETTING HER ACT TOGETHER...THIS IS GOING TO BE A TROPICAL STORM WITHIN THE NEXT 8 HOURS..STRONG CONVECTION IS BUILDING AROUIND THE CENTER AND ITS INCREASING LOOKS REALLY GOOD ON SAT PIC..


Hurrkat05, what's a trochoidal oscillation?
Member Since: November 24, 2005 Posts: 635 Comments: 26543
559. xcool
LAKE
PONTCHARTRAIN
is me
Member Since: September 26, 2009 Posts: 2 Comments: 15618
Landlubbers cant see a "Duck on a Frozen Pond in Hades for the trees"..

Member Since: July 3, 2005 Posts: 419 Comments: 127355
MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. BONNIE COULD REGAIN TROPICAL STORM STRENGTH AS IT MOVES
ACROSS THE GULF OF MEXICO. AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT IS ENROUTE TO INVESTIGATE BONNIE.
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Bonnie still a TD..
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555. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15618
just took a snap of the hot tower since it is to my direct west...but I don't think it will come out well. I can tell you it is a huge feature easily viewable from the coast in relation to the rest of the cloud structure. cool patrap
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552. IKE
BULLETIN
TROPICAL DEPRESSION BONNIE INTERMEDIATE ADVISORY NUMBER 6A
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032010
800 PM EDT FRI JUL 23 2010

...CENTER OF BONNIE EMERGES INTO THE EASTERN GULF OF MEXICO...


SUMMARY OF 800 PM EDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...26.4N 82.5W
ABOUT 445 MI...715 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 45 MI...75 KM WNW OF FT. MYERS FLORIDA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/HR
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 17 MPH...27 KM/HR
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* DESTIN FLORIDA TO MORGAN CITY LOUISIANA...INCLUDING LAKE
PONTCHARTRAIN

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 PM EDT...0000 UTC...THE CENTER OF TROPICAL DEPRESSION BONNIE
WAS LOCATED NEAR LATITUDE 26.4 NORTH...LONGITUDE 82.5 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST-NORTHWEST NEAR 17 MPH...
27 KM/HR. THIS GENERAL TRACK WITH A DECREASE IN FORWARD SPEED IS
EXPECTED DURING THE NEXT TWO DAYS. BONNIE IS EXPECTED TO CROSS THE
EASTERN GULF OF MEXICO TONIGHT AND SATURDAY AND REACH THE NORTHERN
GULF COAST LATE SATURDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. BONNIE COULD REGAIN TROPICAL STORM STRENGTH AS IT MOVES
ACROSS THE GULF OF MEXICO. AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT IS ENROUTE TO INVESTIGATE BONNIE.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB...29.80 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...WINDS WILL CONTINUE TO DECREASE IN SOUTH FLORIDA WHILE
TROPICAL STORM FORCE WINDS MAINLY IN SQUALLS WILL LIKELY BEGIN
ALONG PORTIONS OF THE NORTHERN GULF COAST WITHIN THE WARNING AREA
ON SATURDAY.

RAINFALL...BONNIE IS EXPECTED TO PRODUCE TOTAL RAINFALL
ACCUMULATIONS OF 1 TO 3 INCHES OVER PORTIONS OF SOUTHEASTERN
LOUISIANA...SOUTHERN ALABAMA...SOUTHERN MISSISSIPPI...AND THE FAR
WESTERN FLORIDA PANHANDLE...WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS
OF 5 INCHES. ADDITIONAL RAINFALL AMOUNTS OF 1 TO 2 INCHES ARE
POSSIBLE OVER CENTRAL AND SOUTH FLORIDA THROUGH THIS EVENING.

STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 3 TO 5 FEET ABOVE
GROUND LEVEL ALONG THE IMMEDIATE COAST NEAR AND TO THE RIGHT OF
WHERE THE CENTER MAKES LANDFALL ON THE NORTHERN GULF COAST.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1100 PM EDT.

$$
FORECASTER BEVEN


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Thad Allen I advise that you send the crew back out the rig, looks like some showers and an occasional gusts over 30mph. Lets kill that well...
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Quoting Patrap:
"Boinnnng"




Is that your official desription Pat?
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Well on radar I see 30degrees of a wall forming she just needs 330 degrees more.
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Quoting Tazmanian:
good bye BONNIE good bye BONNIE good bye BONNIE


see you next year

Nope. We won't see her until 2016.
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Quoting MiamiHurricanes09:
Actually in 6 years. Lol, sorry, had to do it.



thats ok
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Quoting fallinstorms:
bonnie is gone even WU got rid of her

No... it's still on the weather underground website.

Tropical Depression Bonnie
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545. IKE
RUKM?

...CENTER OF BONNIE EMERGES INTO THE EASTERN GULF OF MEXICO...
8:00 PM EDT Fri Jul 23
Location: 26.4°N 82.5°W
Max sustained: 35 mph
Moving: WNW at 17 mph
Min pressure: 1009 mb
Member Since: Posts: Comments:
Quoting fallinstorms:
bonnie is gone even WU got rid of her





i like you your funny


you sould be dr m back up when dr m gos a way for two weeks
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Quoting Tazmanian:
good bye BONNIE good bye BONNIE good bye BONNIE


see you next year
Actually in 6 years. Lol, sorry, had to do it.
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dusts off the book, checks off June, checks off July, ok made it through 2 months, lets see what the big months bring
Member Since: Posts: Comments:
Quoting HouGalv08:
Might power a handheld fan at the most. Only way to go is with a backup genny, IMO. Had one after Ike blew thru Houston in '08, and what a godsend. 7kw wired to the house kept it ALL running, except the main A/C unit. We went 14 days that way. Stored away 80 gallons fuel before it hit. Eco drive on the Honda let us use very little fuel, and was quiet too, compared to all the other "screamers".


Yeah a generator's nice. But we didn't have a house to run one at after Rita. Or if you evacuate sometimes be nice to have. After Ike our generous electrician neighbor leant us a generator ran all but the central. The window air was nice though. :) But it was a lot cooler after Ike than Rita. Don't know if we could run the window ac in that heat without over taxing the whole thing.
Member Since: August 15, 2008 Posts: 10 Comments: 3665
So what's going on with the ULL thats killing "Bonnie"?
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538. IKE
Dedicated to the spurious bumbling Bonnie...Link
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Itsa Alive,,"ALIVE" I tell you...!

Member Since: July 3, 2005 Posts: 419 Comments: 127355
good bye BONNIE good bye BONNIE good bye BONNIE


see you next year
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Quoting fallinstorms:


doesn't subtropical mean, tropical wave in fancy terms?

thought it did

Subtropical Cyclone:
A non-frontal low pressure system that has characteristics of both tropical and extratropical cyclones. This system is typically an upper-level cold low with circulation extending to the surface layer and maximum sustained winds generally occurring at a radius of about 100 miles or more from the center. In comparison to tropical cyclones, such systems have a relatively broad zone of maximum winds that is located farther from the center, and typically have a less symmetric wind field and distribution of convection.
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new update and two comes out at any time now
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where the hell is the storm?!
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Member Since: July 3, 2005 Posts: 419 Comments: 127355
Quoting Levi32:
Keep in mind that the eastern Pacific is behind schedule so far with 4 named storms, and the west Pacific is having possibly the slowest start to their typhoon season in history. The Indian Ocean is near-normal I believe with the 3 storms they had in their first season peak. The Atlantic is ahead of schedule with 2.

What does this tell us? The heat pumped into the tropics by the El Nino this past winter is not just going to go away. With the Pacific shut down the heat has to be released somewhere else. It has been all bundled up in the Atlantic which is why we've been seeing the record SSTs and very low surface pressures, the lowest found on the globe right now relative to normal. That heat has to go somewhere to balance the earth's energy budget. The La Nina gives the atmosphere a mechanism with which to deal with that excess heat, and that mechanism is tropical cyclones.


Yes--This is true. The amount of energy focused in the Atlantic Basin will not be denied. How will the energy manifest itself? Will it be 20 or so storms with 4 to 6 intense hurricanes or could it be 15 storms with 8 to 10 intense hurricanes? Will we have record breaking numbers for 4 to 8 weeks? How many records have been set since 1995? The bottom line is that the energy is available for a big season with the heart of the season rapidly approaching. The expected storm track right along the island chain is looking pretty good which puts the Islands, Bahamas, and all the US Coast from Hatteras to Brownsville at substantial risk.
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soon will be saying X BONNIE
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is bonnies LLC offshore of ftmyers- naples?
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I like to beat a dead horse so to speak. But I have not seen better cloud spin on the two blobs that are n. and s. of Hispaniola this season. They are getting better by the frame. Seen most fizzle but ?.
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Quoting louisianaweatherguy:
Pay attention to the flare-up just to the North of the COC... it's trying to come back...

whats the best way to see what the current shear is? It looks as though the ULL has slid more to the west recently and the shear has come down...

INTERESTING...


Nope...howling southeasterly flow aloft is still there and isn't going anywhere.

Upper winds:



Wind Shear:


Member Since: November 24, 2005 Posts: 635 Comments: 26543
latest sat obs show thunderstorms have increased along the nw side of bonnie
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Quoting gordydunnot:
It's got one thunderstorm.


looks like three now LOL
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La,La..la..

Member Since: July 3, 2005 Posts: 419 Comments: 127355
Checks radar, looks at satellite.....



NEXT!!
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Member Since: July 15, 2006 Posts: 168 Comments: 53285
Bonnie is fully tropical.
Member Since: November 24, 2005 Posts: 635 Comments: 26543
Quoting fallinstorms:
bonnie is subtropial now

not even fully tropical lol

No reason why it should be subtropical.
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Pay attention to the flare-up just to the North of the COC... it's trying to come back...

whats the best way to see what the current shear is? It looks as though the ULL has slid more to the west recently and the shear has come down...

INTERESTING...
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"Da, Dum"..

Member Since: July 3, 2005 Posts: 419 Comments: 127355
Quoting MiamiHurricanes09:
Despite having an unfavorable environment in the upper levels I would give the weak trough over Hispañiola a "10%" chance. The GFS appears to take upper level winds to around 5-15 knots around the system in 42 hours so it may have a slight chance.



yup
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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.