Tropical Storm Bonnie Makes Her Debut

By: Dr. Jeff Masters , 4:32 AM GMT on July 23, 2010

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Hi everybody, this is Dr. Rob Carver filling in for Jeff on the late shift.

Based on information from Hurricane Hunters, the National Hurricane Center upgraded TD Three to Tropical Storm Bonnie. As of the 11PM EDT advisory, Bonnie was at 23.4N, 76.5W which is 285 miles southeast of Miami, Florida. Bonnie has maximum winds of 40 mph, a minimum central pressure of 1007 mb, and is moving to the northwest at 14 mph. Bonnie will pass over the Everglades/Florida Keys Friday and cross into the Gulf of Mexico Friday night/early Saturday morning. Tropical storm warnings are in effect for both Florida coasts south of Lake Okeechobee to Key West.


Fig. 1 IR satellite image of Tropical Storm Bonnie at 1216AM EDT.

Threats
NHC is expecting 2-4 inches of rain over south Florida due to Bonnie and 3-5 inches over the Bahamas. They are forecasting a storm surge of 1-2 feet. Tropical storm force winds are expected in the Bahamas starting Thursday night, and they are forecast to arrive in southern Florida Friday morning.

Impacts and Emergency Preparedness
As of 1130PDT EDT, the Key West NWS office is indicating that there are no evacuation orders in effect or planned for Monroe County (the Keys). Small craft are being advised to stay in port and be well secured to their docks. Two shelters will be opened, Key West High School and Stanley Switlik Elementary School in Marathon.

Most of the ships at the Deepwater Horizon oil spill site and other skimming ships have been ordered to seek safe harbor. In the statement, Adm. Allen said ships that operate the ROVs will be the last out and the first back to keep the wellhead observations going as long as possible.

Forecast/Model Assessment
The track models and ensemble models show remarkably good agreement for Bonnie's path across south Florida and towards southeast Louisiana. The current intensity forecast calls for Bonnie to maintain strong tropical storm force winds (40-50 knots) until it makes landfall in Louisiana, with a 15% chance of becoming a hurricane before then. However, the global models (GFS, Canadian GEM, NOGAPS) and the hurricane dynamical models (GFDL, Navy GFDL, and HWRF) do not intensify Bonnie at all. The statistical models (SHIPS and LGEM) support the intensity forecast.

I'm inclined to take the predictions of global and dynamical models with a large grain of salt. When I reviewed the latest model runs (18Z and 12Z), it was apparent that none of the models had a good initialization of Bonnie's structure. Bonnie has a relatively small circulation, so it's easy for the models' initialization to act like there isn't much of a storm there. Without accurate starting conditions, any model will have trouble producing an accurate forecast. NHC has a good summary of the different forecast models they use.

Next Update
Jeff will have an update sometime Friday morning.

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247. xcool
OracleDeAtlantis delete posting plz
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Quoting scott39:
Levi, I respect you and I know that you know your stuff, look at the current Sat., Bonnie looks like her center is a little farther N and shes really pulling it together.


Yes on IR imagery, very bad for locating a surface center and looks can be deceiving. I don't see it under the convection. We won't know for sure from satellite until first light visible images in the morning, but recon will confirm this for us very shortly.
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Quoting atmosweather:
If the LLC was under the middle of that ball of convection, it would be around 24.6N 77.3W...RECON does not support that...ENE winds reported due W of that location...that means the center is somewhere to the S or SE of there.


actually that is incorrect as 78.4 is well to the west of the system, that is inconclusive to me

ENE winds mean they are on the WSW side of the storm
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Bonnie has a very good COC and now Bonnie is increasing in areal intensity and coverage.
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Quoting NCHurricane2009:


I see, extrapolate that, looks like its SE of Andros, probably the storm is 50 mph winds right now at its strongest.

Levi, what do you think about the latent heat theory in post 208 and the upper low both imparting a more northward drag than we are currently thinking. That's what concerns me.


Yeah you're talking about a relocation of the center under the deepest convection, which does happen, but I doubt so here. The area for pressure falls is favorable to the south, not north, and such a convective burst would have to be sustained very strongly for hours upon hours...at least 12, to try to pull the surface center in. Remember some of our ghost invests in May and June...91L and 92L, had MCCs for many hours but didn't succeed in pulling the surface center in even then.
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to me it looks like the old center died out on satellite
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Quoting TampaSpin:
CCHS you are all set up to go....Thanks!


Thanks. I'll probably wait for the 2AM advisory to post a blog.
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Quoting Levi32:
This is what it looked like overlaid on clouds....clearly south of the convection at the time. Taken 3 hours ago:

Levi, I respect you and I know that you know your stuff, look at the current Sat., Bonnie looks like her center is a little farther N and shes really pulling it together.
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A hint for those (like me…my primary is a Dell Studio 17 HD laptop…very compact hi-res display) who find themselves squinting at the small graphics, I found a work around for magnifying graphics and images without pixilation…go to Start/All Programs/Accessories/Ease of Access/Magnifier (Windows 7). Once open, just click on the plus button. You will see your screen blown up…but clear as a bell…so to speak…you move around the image by moving your mouse pointer…takes a little getting used to…once you are done, just click the minus until you are back to 100 percent. Since I found this little tool, life has become so much easier for my “older” eyes. Hope this helps…

v/r

Jon
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Quoting Levi32:


Current run is 00z but some of the models haven't come in yet for 0z like the GFDL and HWRF which will be out within the hour.


Ok. Thanks. :)
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232. xcool
TampaSpin hey dady lmao ha
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Hurricane Hunters are now encroaching on the convective mass now.
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gotta give it to you Levi....that would require some serious northerly relocation...

Quoting Levi32:


Key is to look at the loop....tune it back to the frame at which the ASCAT pass was taken, note the ASCAT position of the center, and then loop forward to the current frame. Extrapolate and ask yourself whether the center could be directly under the convective ball right now. It wasn't that long ago.
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I'm hearing a lot of what sounds like broken records here.
Member Since: August 18, 2008 Posts: 0 Comments: 3113
ONE THING IS CERTAIN IF THE LLC IS UNDER THAT CONVECTION OHHHH BOY LOL WERE IN FOR SOMETHING
Member Since: July 21, 2010 Posts: 0 Comments: 1163
227. xcool
P451/ nono so sorry
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If the LLC was under the middle of that ball of convection, it would be around 24.6N 77.3W...RECON does not support that...ENE winds reported due W of that location...that means the center is somewhere to the S or SE of there.
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Quoting Levi32:
This is what it looked like overlaid on clouds....clearly south of the convection at the time. Taken 3 hours ago:



I see, extrapolate that, looks like its SE of Andros, probably the storm is 50 mph winds right now at its strongest.

Levi, what do you think about the latent heat theory in post 208 and the upper low both imparting a more northward drag than we are currently thinking. That's what concerns me.
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Quoting P451:


That's what I've been seeing. Center is south of the convection. This is a poorly organized system. The satellite presentation isn't indicative of the actual system.

Of course, as we all well know, the plane finds a 50mph wind gust in some random T-Storm within 250 miles of the center? It'll be upgraded to a 50mph TS.

Then it'll make landfall and the highest gust recorded will be around 40mph.




Well actually the NHC is usually quite conservative with the winds that the recon finds, and is more often slow to upgrade based on random SFMR readings. Flight-level winds guide them a lot more.
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CCHS you are all set up to go....Thanks!
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Quoting scott39:
I also believe based on the last news update, that this will be SE LA event at this time!


I think the models will shift even further east. Bonnie wants to move NW longer than expected..IMO.
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Gotta post this message sent to me on my WebSite....this is why i do what i do....I don't think this person would mind since no name is mentioned.....i posted this exactly as written....


I am a 71 year old widow with 2 small dogs living alone 20 miles north of Galveston Tx. (Boy that is a cliche if ever there was one.) I also have a horse and I run from hurricanes, taking dogs and hauling the horse with me. I have done this for 43 years since we moved here in 1967. Recent evacs, Rita 2005, Ike 2008. Alex could be my first one alone, husband died shortly after Ike. I dont understand everything I read on the blog, husband did and I tried to learn from him. I am going to need help. Thanks for your help.



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Quoting Goldenblack:
Three hours ago, I would have agreed, but appearance is much better since...this is a strange little bugger isn't she?



Key is to look at the loop....tune it back to the frame at which the ASCAT pass was taken, note the ASCAT position of the center, and then loop forward to the current frame. Extrapolate and ask yourself whether the center could be directly under the convective ball right now. It wasn't that long ago.
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Quoting bballerf50:
Levi, how can it sustain that shape if its not over the center?


Mid-level centers can be very deceiving and can make systems look very healthy. A track to the northwest is more lucrative for strengthening if Bonnie were to take it, and that's why the mid-level center looks pretty good right now taking that path, but the surface center is not following and thus the storm is not strengthening.
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Three hours ago, I would have agreed, but appearance is much better since...this is a strange little bugger isn't she?

Quoting Levi32:
This is what it looked like overlaid on clouds....clearly south of the convection at the time. Taken 3 hours ago:

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Quoting atmosweather:


We've seen it many times before. Ernesto in 2006 was one example I remember clearly.


Yup, Looked impressive just before landfall. But stayed as a 45mph tropical storm.
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213. 7544
wow cmc was right all along on where bonnie will go to so fla could it right when it also showed her rapidly intensifing right in the spot shes in now we beetr hope not cause it did show a cat 1 into so fgla i guess dmax will soon tell us
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Quoting Goldenblack:
You are right tennisgirl....I just don't see a storm maintaining good convection with an exposed center, even at D Max....

I am assuming (laughs) that your handle makes you a tennis player....Avid player here.



Very much so. love me some tennis.
I think Bonnie may surprise some - but still a tiny little storm, so won't effect a large area.
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I also believe based on the last news update, that this will be SE LA event at this time!
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Look out Alligators.
Member Since: August 18, 2008 Posts: 0 Comments: 3113
Quoting Levi32:


Yeah I mentioned it...it's 3-4 hours old but that only strengthens the argument that the center is south of the convection.



To be honest, I can't see how reliable ASCAT is scanning the Bahamas region since its a broken island chain and I don't see how it can be too accurate. In addition, that is over 4 hours old and much has changed in satellite appearance.
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Quoting tennisgirl08:


I was kinda thinking the same thing. The 11pm NHC advisory mentioned something about a more northward component.


That theory is not impossible. The basic principle of thunderstorm latent heat warming is that you drop surface pressures and rise upper atmospheric pressures in the column of latent heat release. The thunderstorms north of Bonnie's center could be releaseing enough latent heat to the north of the current center, allowing surface pressure falls N of center and slip underneath to the N.
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This is what it looked like overlaid on clouds....clearly south of the convection at the time. Taken 3 hours ago:

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Member Since: August 18, 2008 Posts: 0 Comments: 3113
205. xcool
RECON WE FIND 50MPH WINDS IMO
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You are right tennisgirl....I just don't see a storm maintaining good convection with an exposed center, even at D Max....

I am assuming (laughs) that your handle makes you a tennis player....Avid player here.

Quoting tennisgirl08:


I was kinda thinking the same thing. The 11pm NHC advisory mentioned something about a more northward component.
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Quoting NCHurricane2009:


Okay, here's the deal. Looking at the image in post 156, if the center is E of Andros, this storm is under that organized convection, and we are talking about a storm that could be strengthening faster than the NHC official forecast. But if its SE of Andros, then this is not as strong as it looks.

I heard some mention of ASCAT passes going around. Does anyone have a link, I want to see the latest pass and the time at which the pass was taken.


Yeah I mentioned it...it's 3 hours old but that only strengthens the argument that the center is south of the convection.

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Quoting cchsweatherman:
Recon will soon tell the truth regarding the low level circulation and whether or not its underneath the convection. I really don't see how a storm could be organized with such a satellite appearance without a low level circulation underneath the main convective mass.


We've seen it many times before. Ernesto in 2006 was one example I remember clearly.
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Bonnie is starting to look better to me right now! I dont see any exposed LLC either. She looks like shes tightning up into a small stronger TC! IMO-- Will see
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Quoting cchsweatherman:
Recon will soon tell the truth regarding the low level circulation and whether or not its underneath the convection. I really don't see how a storm could be organized with such a satellite appearance without a low level circulation underneath the main convective mass.


I agree with you 100 %. It looks like the start of a baby cane if you put the center at right in the middle of the convection
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197. 7544
how long will the hh be in bonnie ?
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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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