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 Hurricanes101:
As pathetic as the overreactions to some systems are, it is even more pathetic when people bait them and try to make fun of them if they are wrong

grow up people, its ok to be wrong, its not ok to throw other peoples' predictions in their faces


If they'll stop with the "I won!!!" posts, we'll stop calling them out.

So many people get on here, post accurate information, and don't brag about their "success".
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Hmmm, maybe we are looking at the wrong entity? An 80 knot wind in the southern GoM? (j/k, obviously an error.)



An obvious indication that no QC is conducted on ship obs...
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StormW, can I ask you a question?
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If you have a GR2, nice hook echo just northeast of Hoboken, NJ. TVS is headed SE into midtown Manhatten - gate to gate shear over the Hudson River right now. Most likely, there is a tornado on the ground.
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Quoting StormW:
IR2 LOOP

Storm, the wave off PR, to much shear for development???
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756. IKE
Quoting hurrkat05:
WELL ILL BE BACK AT 11PM WITH A NEW UPDATE...BONNIE WILL BE SOMETHING TO DEAL WITH THE CONDITIONS ARE COMING TOGETHER ..THE ULL IS MOVING FURTHER AWAY FROM BONNIE AND BONNIE IS LOWING DOWN NOT GOOD AT ALL...ILL BE BACK WITH MORE INFO FOR THOSE WHO CARE ABOUT LA AD MISS AT 11PM...


Go ahead and shut the office down.


Look at your blob dying off.....quickly.....

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Quoting MiamiHurricanes09:
Unofficial data...don't rely on it. We won't know if Bonnie is "dead" or not until the 11 P.M EDT advisory.
it appears to building some pretty good thunderstorms near the center. is that a surprise to people in here. i dont know alot and just looked at the satellite image. was not suppose to rain much in the niceville area but it has been pourin at my house. looks like more may be coming from our dying storm.
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Interesting...the ATCF site input the pressure and wind speed from the Vortex message into their latest "update", if you will.

AL, 03, 2010072400, , BEST, 0, 263N, 826W, 30, 1010, TD,

invest_DEACTIVATE_al032010.ren
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Live feed from storm chaser in Queens, NYC...
Link
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well all it done and gone so we move on too the next



see you guys on monday wont be on this weekend
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Quoting CybrTeddy:


Not so, they issued a vortex message for a 94L in 2008 that was off the coast of Florida in September, NHC never named it.


Eh, no reason to deactivate a closed vortex with 31-knot winds.
Member Since: November 24, 2005 Posts: 635 Comments: 26699
Quoting Orcasystems:


Dead and Vortex Plot.. does not compute does it?


no it don't compute
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Well, you never know I suppose. Bonnie could still be a tropical cyclone. NHC might still keep it around.. but I don't think Bonnie will ever gain TS status back.
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Quoting CybrTeddy:


Not so, they issued a vortex message for a 94L in 2008 that was off the coast of Florida in September, NHC never named it.


but there was no deactivation of 94L 15 minutes later

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Quoting StormSurgeon:


There's some rough weather up there Aussie. Some bad weather up around Chicago today also.

I have bad weather off the coast, i hope it stays there. Link
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Quoting StormW:


Don't know!


What do you call an entity that rises from the dead........a Phoenix.........or a zombie?
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Quoting MiamiHurricanes09:
Unofficial data...don't rely on it. We won't know if Bonnie is "dead" or not until the 11 P.M EDT advisory.


Dead and Vortex Plot.. does not compute does it?

Member Since: October 1, 2007 Posts: 81 Comments: 26512
Just moved to Spring Hill Fl. last August. So this is my first real weather experience from a named storm. Officially.
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Quoting Hurricanes101:


has to be a mistake actually, they just did a vortex message, they don't do that on systems they are going to deactivate


Very good point...might just be an error.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting Hurricanes101:


has to be a mistake actually, they just did a vortex message, they don't do that on systems they are going to deactivate


Not so, they issued a vortex message for a 94L in 2008 that was off the coast of Florida in September, NHC never named it.
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Quoting CybrTeddy:
There is no chance Bonnie will regenerate, that ends my discussion with this system.


I disagree, I think the atcf site made a mistake, recon just did a vortex message not 15 minutes ago
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Quoting Hurricanes101:


03? they just deactivated bonnie?
Quoting CybrTeddy:


Looks like Bonnie's dead now.. opened up into a wave.
Unofficial data...don't rely on it. We won't know if Bonnie is "dead" or not until the 11 P.M EDT advisory.
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Quoting StadiumEffect:
Vorticity has increased slightly just south of Haiti...now overlay that with the IR. Watch this area for persistance. Link


I was talking about the thunderstorms over PR.
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Quoting CybrTeddy:


Looks like Bonnie's dead now.. opened up into a wave.


has to be a mistake actually, they just did a vortex message, they don't do that on systems they are going to deactivate
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There is very little chance of Bonnie regenerating.
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Quoting StormW:


Don't know!


He's typing on the blog - LOL!!

(Couldn't resist!)
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Quoting zebralove:
I for one was very excited to experience my first tropical storm ever, or depresion whatever... really we just got rain all day but Spring Hill is close enough I was able to call family in Washington State and say we were in our first storm. Very glad it wasnt too exciting and glad no major damage or deaths etc. I really enjoyed my Bonnie experience. Thank you all for making the blog watching so much fun!


If not too forward, where are you?
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Quoting fldude99:


This is one of the most immature idiotic posts I've ever seen


how?
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Quoting fldude99:
[snip]
Followed by what, exactly?
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thank you very much!
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Quoting MiamiHurricanes09:
Lol, they never renumbered Bonnie. Now they just deactivated it.

invest_DEACTIVATE_al032010.ren


Looks like Bonnie's dead now.. opened up into a wave.
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Hello Everyone,I believe this is the first time strong convection is firing up under the COC, This could get interesting, I am not saying this will be a Strong Hurricane by no means, But I know yall remember Hurricane Charley, He was a very small little powerful storm. The point I am trying to make is,In my opinion, smaller storms with well defined COC's don't have to have perfect conditions to intensify, As long as the storm stays small, the more a chance of it intensifying.You can tell by looking at the WV imagery she is getting plenty of moisture to work with,In my opinion, We could be looking at a Strong Tropical Storm at landfall or a Very Weak Hurricane.Bonnie is not dead by no means,Even some of the computer models,VERY FEW, agree with me lol. We shall see, I predicted this to be a 50mph-80mph storm 2 days ago,50 miles on either side of the Mouth of the Mississippi River.. I may be wrong?? See ya.. Everyone have a good evening..
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Quoting MiamiHurricanes09:
Lol, they never renumbered Bonnie. Now they just deactivated it.

invest_DEACTIVATE_al032010.ren


03? they just deactivated bonnie?
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Quoting AussieStorm:

there is tornado warning for Manhattan/NYC


There's some rough weather up there Aussie. Some bad weather up around Chicago today also.
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Quoting zebralove:
I for one was very excited to experience my first tropical storm ever, or depresion whatever... really we just got rain all day but Spring Hill is close enough I was able to call family in Washington State and say we were in our first storm. Very glad it wasnt too exciting and glad no major damage or deaths etc. I really enjoyed my Bonnie experience. Thank you all for making the blog watching so much fun!


This is one of the most immature idiotic posts I've ever seen
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Quoting sammywammybamy:


HERE:

Bonnie is firing convection(RED)

Yet, still a dry layer there. Sounding from Tampa ~40 minutes ago:



Don't count on it persisting.
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Quoting BenBIogger:


Ahem!
Vorticity has increased slightly just south of Haiti...now overlay that with the IR. Watch this area for persistance. Link
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no hook, should be ok
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Quoting homelesswanderer:


Ah ok. Thanks. :) Should've thought of that. Kind of like what the ULL did with Bonnie when it helped her convection. I think.


Exactly.
Member Since: November 24, 2005 Posts: 635 Comments: 26699
Quoting TexasHurricane:
Does this bear watching or are conditions unfavorable?


Shear isn't that convective for development.


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Quoting nrtiwlnvragn:


Funny they have yet to deactivate TD2 (al022010).


Karen's remnants?
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Levi....I understand your point. As a young man, I found myself eager to debate and prove otherwise in may instances, whether popular or not. I would encourage you, as someone who is remarkably gifted and has a nose for tropical weather at an unbelievably young age, to not sweat the small stuff and to focus on what you can control. Your contributions to this blog are invaluable, don't let contentious points distract you when blogging or in everyday life. There are many who enjoy all your objectivity.
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Quoting Levi32:


Not really. Convection in the southern gulf is slowly trying to extent eastward away from 98L because the upper low is enhancing divergence in that area as it backs west, and will tend to support convection to its southeast over the central and SW gulf. The whole thing has little to do with Bonnie, and the convection will never build east into Bonnie's territory.


Ah ok. Thanks. :) Should've thought of that. Kind of like what the ULL did with Bonnie when it helped her convection. I think.
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Quoting nrtiwlnvragn:


Funny they have yet to deactivate TD2 (al022010).


LOL
Member Since: November 24, 2005 Posts: 635 Comments: 26699
Considering you're not converting it to percentages, as the original poster had originally converted it to percentages, it would be exactly what the poster posted.... 0.5% Now..since the poster put 0.5% it means just that, one half of one percent of a chance. If the poster was referancing a 50% chance, the OP would've put "50.0% or 50% chance". But alas, he did not.
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Quoting nrtiwlnvragn:


Funny they have yet to deactivate TD2 (al022010).
Lol, they never renumbered Bonnie. Now they just deactivated it.

invest_DEACTIVATE_al032010.ren
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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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