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 ElConando:
Bonnie did give me more winds then Ernesto ever did. Give it that.


Ernesto was a very very lucky break for FL. It took the exact worst path in terms of land interaction. That storm had the chance to be a major hurricane if things had have been just a little bit different.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
1310. Levi32
Quoting Ameister12:

What tropical cyclone?


^^
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1309. Levi32
Quoting gator23:

is Louisiana still under a state of emergency?


I don't know, but it was funny for them to even go there in the first place, and they certainly shouldn't be now.
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LEVI YOU GOT THAT RIGHT..
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1307. SLU
Quoting jasoniscoolman2010x:
MY GOD...LOOK AT ALL THIS DRY AIR.. NO WAY WE ARE GOING TO GET ANYMORE TROPICAL STORM OR HURRICANE WITH SO MUCH VERY DRY AIR..DID YOU PEOLPE SEE ALL THIS VERY DRY AIR..


Typical of July...
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sarahjola: have you seen any evidence of development south of Hispanola?
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Quoting gator23:

is Louisiana still under a state of emergency?


Believe so. I dont think it should be but given the threat for possible flooding and tornadoes I think they might as well continue the state of emergency... just incase
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1304. angiest
A puzzler from the Houston forecast discussion:

Dew point Bonnie has moved into the Gulf but may have a hard time re-
strengthening. Still see minimal if any impacts for southeast Texas from
Bonnie at this time.
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1303. Ossqss
Klystron out of Tampa. Let us hope no major upwelling occurs. The vast majority of the oil is under the surface, via the dispersant injection at the well head .......

http://www.baynews9.com/weather/klystron9?animate=florida

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1302. gator23
Quoting Levi32:


For sure....it was a solid TS coming into Florida. Just small, and not able to produce a bunch of convection to make its presence felt a whole ton.

is Louisiana still under a state of emergency?
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Quoting HURRICANECAT5:
Well, when is the next one coming? Any ideas?


Models are developing a CV system and a system off the east coast in a week or two.
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Quoting atmosweather:


I don't really care if this gets me a 24-hr ban but I'm sticking up for those who are knowledgeable AND who have very welcoming and positive attitudes here. You have zero basis on commenting the way you do towards Levi, and if you really think that you have as much meterological knowledge as Levi and the other GREAT experts here, then you're likely mistaken...but it's nothing compared to the way they ACT on this blog...respectful, informational, answer every question. It's a total disgrace how you can hide behind a screenname and take unnecessary shots at posters that make this blog great.

That's the only think I will say on the subject.


No... not mistaken... Levi is a good forecaster... he has good opinions... and ultimately... seems to be a good guy... but all I'm gonna say is this... We all have our opinions.. we are all entitled to our own opinion... we are dealing with a huge topic here... meteorology.... theres gonna be debate... but I dont wanna be belittled here just because Im new to commenting on the blog... Its ridiculous.
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Quoting atmosweather:


I don't really care if this gets me a 24-hr ban but I'm sticking up for those who are knowledgeable AND who have very welcoming and positive attitudes here. You have zero basis on commenting the way you do towards Levi, and if you really think that you have as much meterological knowledge as Levi and the other GREAT experts here, then you're likely mistaken...but it's nothing compared to the way they ACT on this blog...respectful, informational, answer every question. It's a total disgrace how you can hide behind a screenname and take unnecessary shots at posters that make this blog great.

That's the only think I will say on the subject.


levi stormw cchc mh09 have all been great ty i agree
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Quoting Levi32:
At any rate, this doesn't look like a tropical cyclone:


What tropical cyclone?
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Quoting Levi32:


I'm far from the best on this site.


I respect you for admitting that... most of us commenters are " far from the best" on this site.
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1296. Levi32
Quoting ElConando:
Bonnie did give me more winds then Ernesto ever did. Give it that.


For sure....it was a solid TS coming into Florida. Just small, and not able to produce a bunch of convection to make its presence felt a whole ton.
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1295. pottery
Quoting SLU:


Technology tends to make things even more inconclusive ... it happens in cricket too! lol

):):):)
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Quoting wfyweather:


Experts? No. Experts are the ones working at NHC and other Meteorlogy offices that have degrees in meteorology and PHD and stuff.... I probably have just as much experience as Levi Does... Im just relatively new to posting comments on the blog and I dont blog here so people just dont know that yet


I don't really care if this gets me a 24-hr ban but I'm sticking up for those who are knowledgeable AND who have very welcoming and positive attitudes here. You have zero basis on commenting the way you do towards Levi, and if you really think that you have as much meterological knowledge as Levi and the other GREAT experts here, then you're likely mistaken...but it's nothing compared to the way they ACT on this blog...respectful, informational, answer every question. It's a total disgrace how you can hide behind a screenname and take unnecessary shots at posters that make this blog great.

That's the only think I will say on the subject.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Thank god they moved all the drilling equipment and recovery vessels for the apocalyptic Bonnie! Get in your car and flee this tropical depression before its too late!
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1292. SLU
Quoting chrisdscane:


u do know that the nhc has extremly better satelite loops then they provided for us the ones we link here isa joke lol trust me they know there stuff


I know that they are the professionals but i'd just like to see a little more consistency so that we can get a proper sense of the overall activity at the end of the year.

Depending on who you ask we could have anywhere from 2 to 5 named storms so far ...
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1291. pottery
Quoting Levi32:
They found SSW winds and that's it. I've seen many an open wave where the recon found SSW winds but no closed circulation. They would need to hit due south of the center to know for sure, but no conclusive evidence on this pass yet.


That is what I am seeing as well.
No west winds at all right now (or recently)
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OK... we really need to be watching radar and satellite over the next hour,,, This thing is barely holding on... but it is still a td.... this thing will either open up... or fire new convection within the next few hours... most likely
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1289. Patrap
The Day of the Conf last Nov was the Day after Quikscat Failed ,,so the conversation with Avila was esp cool.
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1288. xcool
jasoniscoolman2010x YEAH DRY AIR WE NEED MJO
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Bonnie did give me more winds then Ernesto ever did. Give it that.
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1286. Levi32
Quoting wfyweather:


Dissing Levi? No. I just think you guys praise him like he is the all mighty of the blog when in reality... he isn't. I know he has forecasting skills.... but no more than a lot of people here..


I'm far from the best on this site.
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1285. Patrap

US-Cuba Hurricane Conference NOLA

Posted by: Patrap, 12:17 PM CST on November 24, 2009
Yesterday I was in attendance here in New Orleans for the US-Cuban Hurricane Conference.
It was a great day of sharing from folks who have been in many a fray, from General Russell Honore, to NHC Forecaster Lixion Avila, and many more..

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MY GOD...LOOK AT ALL THIS DRY AIR.. NO WAY WE ARE GOING TO GET ANYMORE TROPICAL STORM OR HURRICANE WITH SO MUCH VERY DRY AIR..DID YOU PEOLPE SEE ALL THIS VERY DRY AIR..
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Quoting tropicfreak:


Levi knows quite a lot, and if you are dissing Levi, you are dissing StormW and Patrap.


Dissing Levi? No. I just think you guys praise him like he is the all mighty of the blog when in reality... he isn't. I know he has forecasting skills.... but no more than a lot of people here..
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1282. KEEPEROFTHEGATE (Mod)
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1281. centex
East seems to translate into weak.
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Quoting tropicfreak:
I should of listened to Hurrkat, shes right about the ULL.


Not one you want to listen to. Very trollish and usually horribly wrong.
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1279. Levi32
They found SSW winds and that's it. I've seen many an open wave where the recon found SSW winds but no closed circulation. They would need to hit due south of the center to know for sure, but no conclusive evidence on this pass yet.

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1278. xcool



;;;Dominican Republic;;;;;;;;;
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1277. SLU
Quoting pottery:

True enough...
but with more and more information, we are able to see more and more of the pros AND the cons.
Bound to make the job more and more hard to do accurately, I would think.


Technology tends to make things even more inconclusive ... it happens in cricket too! lol
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1276. Patrap

"la..La..La..

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Quoting wfyweather:


Experts? No. Experts are the ones working at NHC and other Meteorlogy offices that have degrees in meteorology and PHD and stuff.... I probably have just as much experience as Levi Does... Im just relatively new to posting comments on the blog and I dont blog here so people just dont know that yet


Levi knows quite a lot, and if you are dissing Levi, you are dissing StormW and Patrap.
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can some1 plz show a pic of africa with satelite pis i wanan see any waves
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Wow heat indexes are still in the 90s here in Richmond Va and its almost midnight. MAN does it feel ugly outside. High pressure is directly over us which is why.

84.3 °F
Clear
Humidity: 77%
Dew Point: 76 °F
Wind: 0.0 mph

Wind Gust: 1.0 mph
Pressure: 29.91 in (Rising)
Heat Index: 94 °F
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Quoting pottery:

When did the recon find the west wind?


The last pass they did. But they also found the low weakening... regardless. this is a 30-35 mph td
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1271. msphar
I'm not seeing much on the horizon. Is this gonna change soon ? I'm of course, looking past Bonnie.
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1270. SLU
Quoting Levi32:


Exactly. Consistency one way or the other is all I would like to see.....far better than making a different call on every storm.


Consistency has been in very short supply so far this season.
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Quoting Levi32:


Indeed, and there is some turning at the 500mb level in its northern portion north of the Dominican Republic, but any center of the disturbance may ultimately materialize farther south.



What the WRF model has shown. Tracks it to the Yucatan.

Edit: It shows it near the Yucatan Peninsula by sometime on Monday.
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1268. pottery
Quoting SLU:


Yeah I remember those systems very well.

I guess they don't want to go about naming every blob on the satellite pics but if a systems meets the specifications then it should be classified accordingly.

I'd like to see less confusion in years to come. It's been happening a lot more these days than say 10 years ago which it strange giving that we have more technology and research to aid us.

True enough...
but with more and more information, we are able to see more and more of the pros AND the cons.
Bound to make the job more and more hard to do accurately, I would think.
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1267. will45
it sure would be nice to have QuikSCAT back
Member Since: July 18, 2009 Posts: 1 Comments: 994
1266. Levi32
Quoting HURRICANECAT5:
Well, when is the next one coming? Any ideas?


Possible home-grown mischief may have to be watched for off the SE coast or near Bermuda late next week, but the following week may see a more likely situation for home brew. The wave near Hispaniola will also have to be monitored on its way west, but is not currently an immediate threat.
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Quoting tropicfreak:


Don't shoot the experts.


Experts? No. Experts are the ones working at NHC and other Meteorlogy offices that have degrees in meteorology and PHD and stuff.... I probably have just as much experience as Levi Does... Im just relatively new to posting comments on the blog and I dont blog here so people just dont know that yet
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Quoting Levi32:


Indeed, and there is some turning at the 500mb level in its northern portion north of the Dominican Republic, but any center of the disturbance may ultimately materialize farther south.



Yeah the better area for low pressure development is south and the better upper level environment is south too.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting atmosweather:


Looks like there isn't really a surface feature there...I think it's a portion of the wave that moved through the islands 2 days ago that just degenerated...but the ULL and the associated mid/upper energy along with the upper divergence is helping convection fire down there. This must be watched later this weekend.


its under a gray circle from the nhc
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I should of listened to Hurrkat, shes right about the ULL.
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1261. centex
Give Bonnie until morning. She has fought off bad environment before. Granted she does not look good tonight.
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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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