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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Quoting Levi32:
Center of Tropical Storm Bonnie:



Levi I honestly believe this is at the boundary of even being a tropical cyclone right now...I have not seen a single W-erly wind reported from surface obs, ASCAT, RECON...I'm not even sure if the LLC is closed.
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Quoting Levi32:


They don't have to fly into the deepest convection. They will do that to find the strongest winds, but when you find rotating winds circling around a point in space, you've found your low center. It can't be anywhere else.


they wil still go into the heavy stuff right?
Member Since: July 21, 2010 Posts: 0 Comments: 1163
ok in 6 hrs this will be back to td
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Quoting Levi32:
Center of Tropical Storm Bonnie:



Thats so weird it looks like our galaxy. :)
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Quoting muddertracker:
Could the 1007.4 reading be because of land? So not trying to argue, just wanting to understand...also, they put up a vortex w/o even flying into the heaviest convection? Just trying to understand..I guess they are sure.


They don't have to fly into the deepest convection. They will do that to find the strongest winds, but when you find rotating winds circling around a point in space, you've found your low center. It can't be anywhere else.

The idea of the lower pressure readings because of being over Andros Island is an interesting one. Could be true, but a potential reason why is not coming to me.
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Could the 1007.4 reading be because of land? So not trying to argue, just wanting to understand...also, they put up a vortex w/o even flying into the heaviest convection? Just trying to understand..I guess they are sure.
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000
URNT12 KNHC 230617
VORTEX DATA MESSAGE AL032010
A. 23/05:55:50Z
B. 23 deg 46 min N
077 deg 50 min W
C. 850 mb 1500 m
D. 22 kt
E. 324 deg 74 nm
F. 071 deg 38 kt
G. 326 deg 64 nm
H. EXTRAP 1009 mb
I. 16 C / 1522 m
J. 18 C / 1500 m
K. 18 C / NA
L. NA
M. NA
N. 1345 / 8
O. 0.02 / 0.01 nm
P. AF305 0403A BONNIE OB 06
MAX FL WIND 38 KT NW QUAD 05:33:00Z
SLP EXTRAP FROM 850 MB
MAX FL TEMP 19 C 339 / 34 NM FROM FL CNTR
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so thosse hot towers r on top of the mid levle circulation?
Member Since: July 21, 2010 Posts: 0 Comments: 1163
Center of Tropical Storm Bonnie:

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386. 7544
so the two dosent include the hh data right so if bonnie is stronger we could see a speacial update sooonn after the hh sends the data ?
Member Since: May 6, 2007 Posts: 0 Comments: 6812
Quoting chrisdscane:


do u think they will


Possible but not probable. 40 or 45mph makes little difference anyway, the storm has not strengthened since the last plane was in there.
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Quoting atmosweather:


Almost all of the rain and gusty winds are on the N-ern side of the storm, so the main impacts will come ashore in S FL and will even be felt in central FL due to the tight pressure gradient with the strong ridge to the N.


Right. There looks like some pretty good circulation and cold high tops in that area on the north side.
Member Since: August 18, 2008 Posts: 0 Comments: 884
23.75N 77.8W, higher pressure, still minimal TS-force winds in this side of the storm or lower.

000
URNT12 KNHC 230617
VORTEX DATA MESSAGE AL032010
A. 23/05:55:50Z
B. 23 deg 46 min N
077 deg 50 min W
C. 850 mb 1500 m
D. 22 kt
E. 324 deg 74 nm
F. 071 deg 38 kt
G. 326 deg 64 nm
H. EXTRAP 1009 mb
I. 16 C / 1522 m
J. 18 C / 1500 m
K. 18 C / NA
L. NA
M. NA
N. 1345 / 8
O. 0.02 / 0.01 nm
P. AF305 0403A BONNIE OB 06
MAX FL WIND 38 KT NW QUAD 05:33:00Z
SLP EXTRAP FROM 850 MB
MAX FL TEMP 19 C 339 / 34 NM FROM FL CNTR
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Quoting Levi32:


40mph. Unless recon finds stronger winds in the NE quad.


do u think they will
Member Since: July 21, 2010 Posts: 0 Comments: 1163
Night all -- thanks for leading the band tonight Levi.
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Quoting muddertracker:
But the pressure there is almost 2 mb higher? I'm confused...lowest pressure wins, right?


The readings are pretty close....it may not be the most well-defined center in the world. We'll shortly see exactly where they choose to put the vortex message.
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Quoting weatherwart:


Maybe, given where the NHC is locating the COC, but look where all the activity is, on the north side. That will come ashore in south Florida, don't you think?


Almost all of the rain and gusty winds are on the N-ern side of the storm, so the main impacts will come ashore in S FL and will even be felt in central FL due to the tight pressure gradient with the strong ridge to the N.
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Quoting weatherwart:


Maybe, given where the NHC is locating the COC, but look where all the activity is, on the north side. That will come ashore in south Florida, don't you think?


That's the point to be made is that the worst weather is north of the center and will still directly impact south Florida, especially the Miami area, even though the center will pass south of them.
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Quoting chrisdscane:
ok some1 answer this before i go to bed what do u think will be the winds at 5 good night


40mph. Unless recon finds stronger winds in the NE quad.
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Quoting Levi32:
Bonnie is headed for the keys....definitely not for the Florida mainland.


Maybe, given where the NHC is locating the COC, but look where all the activity is, on the north side. That will come ashore in south Florida, don't you think?
Member Since: August 18, 2008 Posts: 0 Comments: 884
Quoting chrisdscane:
ok some1 answer this before i go to bed what do u think will be the winds at 5 good night


40 mph at best.
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Quoting Levi32:
There it is! 23.7N 77.9W, just off the SW tip of Andros Island.

But the pressure there is almost 2 mb higher? I'm confused...lowest pressure wins, right?
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Quoting Levi32:


NHC uses that funny 12-hour average motion which hasn't been valid for over 6 hours now. Motion is more WNW.


oh, ok. that can be a bit deceiving. they need to fix that...LOL!
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ok some1 answer this before i go to bed what do u think will be the winds at 5 good night
Member Since: July 21, 2010 Posts: 0 Comments: 1163
Quoting tennisgirl08:


the 2Am says she is still moving NW - which surprised me a little b/c i thought the ridge would have pushed her more westerly at this point. i think she may hit the miami area - extreme southern florida mainland.


NHC uses that funny 12-hour average motion which hasn't been valid for over 6 hours now. Motion is more WNW.
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Quoting TampaSpin:


Should continue for a while until the front grabs it.
ok ..thx
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Quoting NCHurricane2009:


GO LEVI GO! LOL, thanks for posting those images. Now I can go to sleep with certanity of where Bonnie is.

Now, G'night all.


Lol. Goodnight!
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Quoting scott39:
They just did!
Member Since: July 21, 2010 Posts: 0 Comments: 1163
Quoting NCHurricane2009:


GO LEVI GO! LOL, thanks for posting those images. Now I can go to sleep with certanity of where Bonnie is.

Now, G'night all.


Good night NCH!
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Quoting cybergrump:
Cant wait for them to fly into the blob I want to see my self that there is no center there.
They just did!
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Quoting Levi32:
Bonnie is headed for the keys....definitely not for the Florida mainland.


the 2Am says she is still moving NW - which surprised me a little b/c i thought the ridge would have pushed her more westerly at this point. i think she may hit the miami area - extreme southern florida mainland.
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Quoting Levi32:
There it is! 23.7N 77.9W, just off the SW tip of Andros Island.



GO LEVI GO! LOL, thanks for posting those images. Now I can go to sleep with certanity of where Bonnie is.

Now, G'night all.
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LISTEN THE NHC ESTIMATED THAT POSITION
Member Since: July 21, 2010 Posts: 0 Comments: 1163
359. xcool
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358. xcool
CMC call for fL keys
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23.8 77.5 is on the tropical points. It's been that way for hours. Nothing unexpected.
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Cant wait for them to fly into the blob I want to see my self that there is no center there.
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OK guys. I've been a long time lurker and need some insight. Last time I tool a tropical storm lightly I was alone with 6 kids in my house,4 my own two borrowed, and it turned into Hurricane Katrina. I just want your insight....is this something I need to worry about?
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lol hold on they estimated that coc
Member Since: July 21, 2010 Posts: 0 Comments: 1163
You can clearly see where the center of circulation is located on this radar:

Link
Member Since: October 5, 2005 Posts: 2 Comments: 917
Bonnie is headed for the keys....definitely not for the Florida mainland.
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im surprised the NHC didn't raise the winds to 45 mph
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I may be proved wrong by RECON, but I think the HWRF is giving "Boonie" a little extra "bust."

999mb is a little much IMO...
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It goes to show, you cant go off looks, even though I said to. LOL
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I have been expecting the LLC to at least try and reform under some of the deep convection for 6 hours...but it hasn't and here's the problem (Levi has mentioned this): the most favorable areas for a low pressure system to organize is south of the current mid level energy (where the convection is), but with the strong low level easterlies dominating the synoptic pattern, the LLC is pretty much forced W-ward keeping it from trying to reform to the N. It is compounded by the fact that the mid level energy is still moving NW-ward. If the center is going to reform (allowing the storm to intensify), that convection would have to get even deeper and sustain itself all night and all morning...but with 10-15 kts of S-erly shear throwing the cloud tops away from the favorable area to the S, it's going to be pretty hard for that convection not to die out soon.
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There she is...
FULL IMAGE
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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.