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 IKE:
Bumbling Bonnie.

Estimated (by SFMR or visually) Maximum Surface Wind: 22kts (~ 25.3mph)

My blow dryer puts out more wind.


She's decoupled as she can be right now and with the strong easterlies pushing the LLC away from the mid level energy it's not looking good for her. There are still zero reports or indications of westerly winds either from imagery, ASCAT, RECON or surface obs. She could easily have lost her closed circulation.
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Quoting IKE:
Bumbling Bonnie.

Estimated (by SFMR or visually) Maximum Surface Wind: 22kts (~ 25.3mph)

My blow dryer puts out more wind.


Remember that is inbound from the NW. Although I don't doubt Bonnie has weakened.
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445. 7544
thers still dmax not agreeing yet
Member Since: May 6, 2007 Posts: 0 Comments: 6618
444. xcool
homelesswanderer :0
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Comparisons between the same ordinal dates in 2005 and 2010
21July2005

21July2010

5July2005

21July2010

21July2005

21July2010
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an eye? at 1009mb?
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441. 7544
so she stays in check at 40mph right
Member Since: May 6, 2007 Posts: 0 Comments: 6618
440. IKE
Bumbling Bonnie.

Estimated (by SFMR or visually) Maximum Surface Wind: 22kts (~ 25.3mph)

My blow dryer puts out more wind.
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Quoting xcool:
she open wave


I hope so. Got a niece in Baton Rouge. Not cable. No internet. I'm her weather channel. Poor baby. :)
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Quoting KoritheMan:
Still not seeing any westerly winds on satellite imagery. She's having trouble maintaining sufficient low-level convergence, due to her fast forward speed.


The strong low level easterlies are hurting her in a number of ways.
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436. NYX
Well...we're starting to breaking a sweat down here. The last couple of frames look disturbing.

http://www.ssd.noaa.gov/goes/flt/t1/rb-l.jpg
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So far getting toward the end of July is the month of ULL's and dry air. Wonder how long until we get a decent TS or cane? Negative upward motion is spreading into the Atlantic now until almost mid August.
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Quoting 7544:
WHay what happen whats all this talk about a sheard mess


The southerly shear that has been impacting Bonnie is keeping the mid level energy and thus the deep convection N of the low level center of circulation...which means the storm is very vertically tilted and cannot intensify.
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433. xcool
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Still not seeing any westerly winds on satellite imagery. She's having trouble maintaining sufficient low-level convergence, due to her fast forward speed.
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431. xcool
she open wave
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double post deleted
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Here is the vortex:

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 23rd day of the month at 06:17Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 305)
Storm Number & Year: 03L in 2010
Storm Name: Bonnie (flight in the North Atlantic basin)
Mission Number: 4
Observation Number: 06
A. Time of Center Fix: 23rd day of the month at 5:55:50Z
B. Center Fix Coordinates: 23°46'N 77°50'W (23.7667N 77.8333W)
B. Center Fix Location: 95 miles (153 km) to the SSW (199°) from Nassau, Bahamas.
C. Minimum Height at Standard Level: 1,500m (4,921ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 22kts (~ 25.3mph)
E. Location of the Estimated Maximum Surface Wind: 74 nautical miles (85 statute miles) to the NW (324°) of center fix
F. Maximum Flight Level Wind Inbound: From 71° at 38kts (From the ENE at ~ 43.7mph)
G. Location of Maximum Flight Level Wind Inbound: 64 nautical miles (74 statute miles) to the NW/NNW (326°) of center fix
H. Minimum Sea Level Pressure: 1009mb (29.80 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 16°C (61°F) at a pressure alt. of 1,522m (4,993ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 18°C (64°F) at a pressure alt. of 1,500m (4,921ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 18°C (64°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind, Pressure and Temperature
N. Fix Level: 850mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 0.01 nautical miles
Remarks Section:
Maximum Flight Level Wind: 38kts (~ 43.7mph) in the northwest quadrant at 5:33:00Z
Sea Level Pressure Extrapolation From: 850mb
Maximum Flight Level Temp: 19°C (66°F) which was observed 34 nautical miles (39 statute miles) to the NNW (339°) from the flight level center
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428. 7544
WHay what happen whats all this talk about a sheard mess
Member Since: May 6, 2007 Posts: 0 Comments: 6618
Quoting StormThug:
does anyone have the spaghetti model plots?


http://my.sfwmd.gov/sfwmd/common/images/weather/plots/storm_03.gif
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Quoting muddertracker:
This blog is absolutely awesome at 1:30 in the morning (cst) NO arguing, just discussion with folks who understand they can be wrong...night everyone, and thanks!


Night Mudder. I like the midnight crew too. :)
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The vortex message just put in by the current mission compared to the last one is 200 miles away on a heading of 297 degrees.

Over the 13 hour period between fixes (the first one the 1006 fix), Bonnie has been traveling at 15 mph on that 297 heading.

edit: that is just a smidge north of WNW (which is 292.5 degrees)
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does anyone have the spaghetti model plots?
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Quoting Levi32:
Well my confidence in my forecast for Bonnie just got a nice boost, so with that I'm going to turn in. Great discussion tonight with all of you. Goodnight all! Till tomorrow.


Night Levi. :)
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Quoting muddertracker:
This blog is absolutely awesome at 1:30 in the morning (cst) NO arguing, just discussion with folks who understand they can be wrong...night everyone, and thanks!


Night muddertracker!
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mehh im out too see ya at 5 am peeeeeeeeeeeeeace
Member Since: July 21, 2010 Posts: 0 Comments: 1052
ok
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Quoting Levi32:
Well my confidence in my forecast for Bonnie just got a nice boost, so with that I'm going to turn in. Great discussion tonight with all of you. Goodnight all! Till tomorrow.


Good night Levi, great job once more and get some rest!
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416. xcool
open wave
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Something look strange to you in that picture levi?

Quoting Levi32:
Center of Tropical Storm Bonnie:

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Quoting Levi32:
Well my confidence in my forecast for Bonnie just got a nice boost, so with that I'm going to turn in. Great discussion tonight with all of you. Goodnight all! Till tomorrow.

Goodnight!
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This blog is absolutely awesome at 1:30 in the morning (cst) NO arguing, just discussion with folks who understand they can be wrong...night everyone, and thanks!
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Well my confidence in my forecast for Bonnie just got a nice boost, so with that I'm going to turn in. Great discussion tonight with all of you. Goodnight all! Till tomorrow.
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Satellite loops aren't showing much in the way of westerly winds, either. Bonnie may well degenerate back into an open wave.
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Quoting Levi32:


Ya it might be on the edge....got some SSW winds but we need to see a bit more than that. I wish they would have ventured into the SW quad...that would have told us for sure.


They probably are thinking the same thing but it would be extremely unwise for them to declare the system as weakening or dissipating into an open wave at this point close to "landfall". But I would love to see them fly over there and check it out.
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Quoting Levi32:


Lol exactly what I wanted to say earlier but I didn't because a tropical cyclone that looks like a galaxy is usually very healthy, mature, and strengthening. However, Bonnie is none of the above. Mid-level centers can do that lol.


Lol.
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Quoting OracleDeAtlantis:
Although she looks better, configuration wise, the lower level convergence, for the past few hours shows an unhealthy speed.

I'm not convinced this strengthening can be maintained if she's moving really fast, and this appears to be the case. She may already be moving ahead of herself.

On the other hand, the speed hasn't affected her so far, perhaps because of her small size.

Interesting system ...




Well, she isn't strengthening, and hasn't been all day.
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It will probably lose a lot of convection during the afternoon and become an open wave. What a sheared mess 1009mb lol Next...
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Quoting atmosweather:


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.


Ya it might be on the edge....got some SSW winds but we need to see a bit more than that. I wish they would have ventured into the SW quad...that would have told us for sure.
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ok such a small storm
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Although she looks better, configuration wise, the lower level convergence, for the past few hours shows an unhealthy speed.

I'm not convinced this strengthening can be maintained if she's moving really fast, and this appears to be the case. She may already be moving ahead of herself.

On the other hand, the speed hasn't affected her so far, perhaps because of her small size.

Interesting system ...


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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.


Most likely due to land yes. They are extrapolating the pressure also so that doesn't always make the readings accurate.
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Levi, thanks for holding my hand...clearly I need it :)
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Quoting homelesswanderer:


Thats so weird it looks like our galaxy. :)


Lol exactly what I wanted to say earlier but I didn't because a tropical cyclone that looks like a galaxy is usually very healthy, mature, and strengthening. However, Bonnie is none of the above. Mid-level centers can do that lol.
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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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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.