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 NCHurricane2009:


I did see that faint mid-level spin, that map you posted shows upper winds. The upper winds are divergent on the SE side of anticyclonic upper ridging over PR, DR, and Haiti, which triggered those storms. These storms tend to blow up, then die down (right now in a die down phase). There is no surface feature (tropcal wave, surface trough) to sustain that area or give it focus as a surface system (and most tropical cyclones all start as surface systems). So its going to be very difficult for this to develop.


They can surprise from time to time but for now unless the NHC sees somthing in it I'm not gonna pay much attention to it.
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Bonnie's satellite appearance looks exactly like a hurricane symbol. lol
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Quoting reedzone:
Bonnie is one small storm, could compare it to Marco in 2008.. very small systems like to get going fast. I'm holding on to my 60 mph. landfall south of Miami tomorrow..

Photobucket


I was thinking the same reasoning this morning for S FL landfall ranging somewhere between 60 and 90 mph (seems more like 60 now, I'm with you on this one, which is funny LOL because last night I was arguing about the wind shear never letting this develop. After what has happened today, I am with a small tropical cyclone that has potential to briskly strengthen. Its amazing how the shear did a complete 180 form high, to marginal, to low in the last two days. I was caught off guard).
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Quoting NCHurricane2009:


I did see that faint mid-level spin, that map you posted shows upper winds. The upper winds are divergent on the SE side of anticyclonic upper ridging over PR, DR, and Haiti, which triggered those storms. These storms tend to blow up, then die down (right now in a die down phase). There is no surface feature (tropcal wave, surface trough) to sustain that area or give it focus as a surface system (and most tropical cyclones all start as surface systems). So its going to be very difficult for this to develop.


Yeah well it's been there a while and there is the faintest of reflections at the surface. If you remember 97L started out pretty close to this area and at one point it seemed like they were the same system but they were always separate. Bonnie is now more out in front so the distinction between the two is very evident now. It's weak but has time to drift....not an immediate threat but something to keep an eye on that is close to home.
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92. 7544
good call cchs i agree looks at the clod cloud tops and spiral banding
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cmon 2am advis im soo tierd
Member Since: July 21, 2010 Posts: 0 Comments: 1052
Link

Did these move west??
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EVeryone is forgetting one thing! A small system like Bonnie can Intensify very fast. It does not take much to rotate a small system quickly unlike a very large system...but, small systems will also unwind much faster as well.
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Bonnie is gonna be a little baby cane. She is awfully small.
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Quoting cchsweatherman:


There will be a 2AM advisory since watches and warnings are in effect. I would expect a slight increase in strength to about 45 to 50 mph given improving satellite appearance.

and possibly update from HH
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Hurricane Hunters are descending off the South Florida coast and inbound into Tropical Storm Bonnie. Expect some surprises in my opinion.
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Quoting homelesswanderer:
????

...TROPICAL STORM BONNIE...

BASED ON THE NAM BOUNDARY LAYER WIND ANALYSIS THE MODEL PLACES THE
CENTER OF BONNIE ABOUT 40 NM FARTHER S THAN THE TPC/NHC ANALYZED
POSN. THE NAM HAS TRENDED WEAKER OVER THE PAST DAY WITH THE SFC
REFLECTION OF BONNIE... TO THE POINT THAT IT NOW DOES NOT EVEN
HAVE A WELL DEFINED SFC CIRCULATION OVER THE GULF OF MEXICO.
CONSULT THE LATEST TPC/NHC ADVISORIES/DISCUSSIONS FOR FURTHER INFO
ON BONNIE.


Yeah some of the dynamical models have consistently been pessimistic about Bonnie's strength through the GOM...the NAM and Euro in particular have continued to show a very weak low or even an open wave as Bonnie traverses the GOM.
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83. 7544
i doooo wait for dmax 1 hour from now bonnielloks good now she has her show going during dmax dounuts again
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Quoting cchsweatherman:


There will be a 2AM advisory since watches and warnings are in effect. I would expect a slight increase in strength to about 45 to 50 mph given improving satellite appearance.

ya when is it sometimes late
Member Since: July 21, 2010 Posts: 0 Comments: 1052
Quoting Levi32:


Pretty much yep...ridge over the SE US won't really be moving over the next 5 days, so movement of anything around the Caribbean islands will be west to WNW into the Gulf of Mexico and then more likely to recurve in the western gulf than the eastern gulf.


I'll take it more seriously a few days from now. For now I have a TS at my doorstep.
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CMC OZ NOLA
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Quoting texwarhawk:
is there a COC under that ball of convection if you look at the IR rainbow it seems there a banding features all around it? (in the 4:15 UTZ image)



Omg! i was just wondering what if that were the case, thatd be crazy. But isnt the center to the south of that ball?

-btw i haven't been signed into this blog in years!
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Quoting Levi32:


Pretty much yep...ridge over the SE US won't really be moving over the next 5 days, so movement of anything around the Caribbean islands will be west to WNW into the Gulf of Mexico and then more likely to recurve in the western gulf than the eastern gulf.


CMC and EURO been showing that. We'll see.
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Quoting chrisdscane:

ANY WORD on the 2am advis?


There will be a 2AM advisory since watches and warnings are in effect. I would expect a slight increase in strength to about 45 to 50 mph given improving satellite appearance.
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Quoting Levi32:


It's under that area southeast of Bonnie where conditions are more favorable with more ridging aloft. Still not perfect but better than what Bonnie has. If Bonnie was in this area she'd be strengthening nicely right now.



I did see that faint mid-level spin, that map you posted shows upper winds. The upper winds are divergent on the SE side of anticyclonic upper ridging over PR, DR, and Haiti, which triggered those storms. These storms tend to blow up, then die down (right now in a die down phase). There is no surface feature (tropcal wave, surface trough) to sustain that area or give it focus as a surface system (and most tropical cyclones all start as surface systems). So its going to be very difficult for this to develop.
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Quoting code1:
Nice update late in the day. Thanks, it is very much appreciated from more than who post here. Atmos!!! Great to see ya again buddy. ;-)


Code! Good to see you around =) Haven't seen you in a while.
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Quoting code1:
Nice update late in the day. Thanks, it is very much appreciated from more than who post here. Atmos!!! Great to see ya again buddy. ;-)


Hey code!!! Great to see you too! I'm trying to be more productive about getting on the blogs this season LOL!

I still think the LLC is not under the ball of convection, but the movement of the ULL is certainly trying to help Bonnie out...moving steadily W-ward.
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Quoting cchsweatherman:


Look at the large band to the east and the small band to the west.

ANY WORD on the 2am advis?
Member Since: July 21, 2010 Posts: 0 Comments: 1052
????

...TROPICAL STORM BONNIE...

BASED ON THE NAM BOUNDARY LAYER WIND ANALYSIS THE MODEL PLACES THE
CENTER OF BONNIE ABOUT 40 NM FARTHER S THAN THE TPC/NHC ANALYZED
POSN. THE NAM HAS TRENDED WEAKER OVER THE PAST DAY WITH THE SFC
REFLECTION OF BONNIE... TO THE POINT THAT IT NOW DOES NOT EVEN
HAVE A WELL DEFINED SFC CIRCULATION OVER THE GULF OF MEXICO.
CONSULT THE LATEST TPC/NHC ADVISORIES/DISCUSSIONS FOR FURTHER INFO
ON BONNIE.
Member Since: Posts: Comments:
Bonnie is one small storm, could compare it to Marco in 2008.. very small systems like to get going fast. I'm holding on to my 60 mph. landfall south of Miami tomorrow..

Photobucket
Member Since: July 1, 2008 Posts: 13 Comments: 7334
66. 7544
oh oh oh
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you guys are great at answering questions. Here's my next one. where is the ULL expected to be once Bonnie makes it into the GOMEX?
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Quoting chrisdscane:

I STILL DONT SEE "SPIRAL BANDS" PLZ HELP ME SEE WUT UR SEEING CASUE IT LOOKS TO ME THAT THOOSES R OUT RUNNING SHOWERS


Look at the large band to the east and the small band to the west.
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Nice update late in the day. Thanks, it is very much appreciated from more than who post here. Atmos!!! Great to see ya again buddy. ;-)
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Quoting CyclonicVoyage:


Dude, that sat. images is more ominous guys! I think my early afternoon forecast of 60 to 90 mph by S FL (I am now thinking lower end of the forecast, more like 60 mph winds) is possible. That definetly looks more like Bonnie is underneath the storm blob (or should I say storm circle).
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Quoting cchsweatherman:
Given the current satellite appearance and current organization of convection, I'm becoming convinced the low level circulation center is underneath the convective mass. I say this since you don't see spiral feeder band features around a symmetric convective mass unless you have a low level circulation located underneath the convection.

I STILL DONT SEE "SPIRAL BANDS" PLZ HELP ME SEE WUT UR SEEING CASUE IT LOOKS TO ME THAT THOOSES R OUT RUNNING SHOWERS
Member Since: July 21, 2010 Posts: 0 Comments: 1052
Quoting ElConando:


Could it head on the same path as Bonnie generally?


Pretty much yep...ridge over the SE US won't really be moving over the next 5 days, so movement of anything around the Caribbean islands will be west to WNW into the Gulf of Mexico and then more likely to recurve in the western gulf than the eastern gulf.
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Quoting texwarhawk:
is there a COC under that ball of convection if you look at the IR rainbow it seems there a banding features all around it? (in the 4:15 UTZ image)



Very difficult to say without the visible imagery...it doesn't appear to me that the LLC is under the ball of convection.
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Given the current satellite appearance and current organization of convection, I'm becoming convinced the low level circulation center is underneath the convective mass. I say this since you don't see spiral feeder band features around a symmetric convective mass unless you have a low level circulation located underneath the convection.
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I hate to say it but does this seem like dejavu, other than not being a cat1 when she hits florida , she is going over the same exact place that katrina went through , and nothing there to tare it down , but swamps and water ... i really think this thing is going to explode when it hits the hot gulf waters , really really hope im wrong
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ISNT THERE AN ADVISORY COMIN AT 2AM?
Member Since: July 21, 2010 Posts: 0 Comments: 1052
Seems a lot of folks think the LLC is in the center of the convection. I think you have seen the best of Bonnie IMO She is getting stretched from the ULL. I would not be surprised one bit if tomorrow afternoon she becomes an open wave.
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Quoting Levi32:
Just a little reminder that Bonnie isn't the only fish in the sea.....take a peak at the bottom-right corner of Bonnie's floater. There's a bit of mid-level turning going on north of the eastern tip of the Dominican Republic. It shows up on the new CIMSS 500mb vorticity map:



Here's the bigger loop to give it some perspective. I'd keep a wary eye on this area for possible mischief over the next 5 days or so. It could sneak up on the weather map by next week.


Could it head on the same path as Bonnie generally?
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Quoting atmosweather:


That's the one we've both been watching for the last 2-3 days...I like this system's chances for mischief a lot more than Bonnie's...


It's under that area southeast of Bonnie where conditions are more favorable with more ridging aloft. Still not perfect but better than what Bonnie has. If Bonnie was in this area she'd be strengthening nicely right now.

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Quoting robert88:
You guys do realize the LLC is to the S of the ball of convection. This is a very stretched disorganized storm. It is not vertically stacked. http://www.ssd.noaa.gov/goes/flt/t1/flash-ir2.html


Yes, it is on the SE side of the ball.....but, the COC appears to be nearly covered ..hard to tell anything without a visible tho.
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Quoting txsweetpea:


reed...do you think Bonnie will intensify to stronger than a trop storm? Thanks in advance.


That's a hard call.. I'm giving it a 50/50 chance at making Hurricane status. Needs to stay away form that ULL, which it is currently doing. Bonnie is under 10-15 knots of wind shear per the CIMMS shear map.
Member Since: July 1, 2008 Posts: 13 Comments: 7334
Hello TS Misty Breeze. I hope this means lighter traffic tomorrow morning.

I've seen spit takes bigger than Bonnie.
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Quoting txsweetpea:
Is recon flying out right now?


They are about an hour away from making a center fix.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.