Tropical Depression Three forms

By: Dr. Jeff Masters , 3:42 PM GMT on July 22, 2010

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Tropical Depression Three has formed over the Bahama Islands, and appears poised to become Tropical Storm Bonnie later today. Satellite images of TD 3 show a modest area of heavy thunderstorms that have slowly increased in intensity and areal coverage this morning. The surface circulation center is exposed to view, thanks to strong upper-level winds out of the southwest that are creating about 20 knots of wind shear. This wind shear is due to the counter-clockwise circulation of air around a large upper-level low pressure system over Florida that is moving west at about the same speed TD 3 is. Water vapor satellite loops show a large area of dry air is associated with the upper-level low pressure system, and this dry air is hindering development of TD 3. The storm is attempting to wrap a curved band of clouds around its center, on its west side. If TD 3 is able to do this, the center will be protected from shear and dry air, and more significant strengthening can occur. Surface observations in the Bahamas and several nearby ships have shown top winds in TD 3 of up to 35 mph, so the storm is close to the 40 mph winds needed to be classified as a tropical storm.


Figure 1. Water vapor satellite image showing dry air (brown colors) associated with the upper-level low over Florida. Image credit: NOAA/NESDIS.

Track Forecast for TD 3
The storm is in a fairly straightforward steering current environment, and TD 3 should progress steadily to the west to west-northwest through Saturday. This will bring the storm ashore over the Florida Keys or South Florida on Friday, and into the Gulf of Mexico on Saturday. The latest set of model runs from 2am EDT (6Z) had the advantage of having data from a flight of the NOAA jet last night, so we have higher confidence than usual in the track of TD 3 over the next two days. The location of TD 3's final landfall along the Gulf of Mexico coast has the usual uncertainties for 3 - 4 days, with the various models calling for landfall somewhere between the upper Texas coast and the Florida Panhandle coast. Given the uncertainties, the move halt operations in the Deepwater Horizon blowout recovery effort are probably wise.

Intensity Forecast for TD 3
The primary detriment to development of TD 3 for the next three days will be the presence of the large upper-level low to its west. As long as this low remains in its present location, relative to TD 3, it will bring wind shear of about 20 knots and dry air into the storm. This will limit the intensification potential of TD 3 to no more than about 10 - 15 mph per day. If the upper-level low slow down a bit, relative to TD 3, more shear will affect the storm, potentially weakening it. Conversely, if the upper-level low picks up speed and pulls away from TD 3, the storm may be able to intensify at a faster rate. None of the computer models is calling for that to happen, but it would not take much of an additional separation between TD 3 and the upper level low to substantially reduce shear and allow TD 3 to intensify into a hurricane on Saturday. I put the odds of TD 3 making it to hurricane strength in the Gulf of Mexico at 20%.

98L
An area of disturbed weather (98L) has developed in the Gulf of Mexico's Bay of Campeche. This system is under a low amount of shear, 5 - 10 knots, and may barely have enough time to organize into a tropical depression before making landfall along the Mexican coast a few hundred miles south of the Texas border on Friday.

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 between 3 - 4 pm, when the Hurricane Hunters will be in the storm. I'll also speculate on the possible impact the storm will have on the oil spill region.

Jeff Masters

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Each plane has a different cross wind component, as far as headwind, that's pilot discretion. They do close the airport at a certain windspeed though.
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I am not as experienced as Storm, Elconado, Doc, or some of the others but I really dont buy how this cant become a hurricane before making landfall. Something in the ol gut tells me this one becomes a 2/3.
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1270. angiest
Hum, GFDL doesn't seem to know what to do with 98L.
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Quoting TOMSEFLA:
site has changed map logo to bonnie with ts symbol


????
Member Since: July 21, 2010 Posts: 0 Comments: 1118
Quoting hophead:
If it goes over the everglades, any chance of mild intensification similar to TS Fay?


.....and Wilma
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1266. hophead
If it goes over the everglades, any chance of mild intensification similar to TS Fay?
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WAHOO - MY AV IS APPROVED
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site has changed map logo to bonnie with ts symbol
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Storm w this is going to miss S.FL right?

Enough already!!! Asking about airport closings and where the storm is going....
Why are you doing this? At best it's a TS, not a hurricane. Wind and rain so calm down.

Follow what the NHC is saying!!!!!
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Quoting BenBIogger:


Somebody posted a T-skew from the Bahamas that showed a moderate amount of dry air in the mid-levels.

The latest RUC analysis (18Z) shows a decrease from earlier:



The winds are more unidirectional now too, which is a sure sign of lessening shear.
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hi everyone, i am usually just a lurker, but is it just me or are the HH flying around in the area much more north of where the current coc is supposed to be?
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1227. sammywammybamy 7:19 PM GMT on July 22, 2010

They will switch Directions of the runway based on weather do it at FTL all the time
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The ever so reliable TWC just said..."Recon is inside investigating tropical depression 3 to see if it has wind enough to be called Bonnie."
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting MrJoeBlow:


Right it got Sarasota wrote all over it.


I do not see how or why.
Member Since: June 16, 2005 Posts: 0 Comments: 1274
Quoting Clearwater1:


What's your reasoning?


Don't you see how its moving. I seen it go NW and I said yep there right there is going to Sarasota for sure.
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Quoting Baybuddy:
Dead Sea? Btw worst vacation EVER!
\

Did you go in with cuts?
Member Since: September 6, 2009 Posts: 2 Comments: 3712
GUYS I HAVE BEEN DOWNCASTING THIS THING ALL DAY I JUST GOT BACK FROM GOLF AND I MUST SAY IT IS LOOKING GOOD THERE R NOW SIGNIFICANT SHOWERS ON THE WESTERN SIDE AND IT IS NOW MORE CIRCULAR HURRICANE HUNTERS R FINDING TS WINDS AT ITS CURRENT SPPED ITLL BE HERE EARLY TOOMOROR ATLEAST THATS WHAT I THINK TY AND BYE
Member Since: July 21, 2010 Posts: 0 Comments: 1118
is this site even updateing?

Link
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Bonnie will be a TS @40mph @ 5pm


Bonnie is moving WNW near 300dg and should continue on a path near or over Andros Island later tonight and approach the upper keys on Friday. Bonnie might make it up to 50-60mph TS by tomorrow. Drier Air in the GOM might hinder this along with not the best of upper level conditions. It's warrented that Bonnie could wobble west or north alittle making landfall up near Dade county across the glades. Ridge access isnt straight west..so this will continue to move more WNW thru the period.
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Quoting StormW:


South FL. is going to be on the "dirty side"


what is the furthest north you could see this making landfall?
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Quoting sammywammybamy:


Im not flying out..

i was just curious.

IN MIAMI INTERNATIONAL AIRPORT. FLIGHTS TAKE OFF TOWARDS THE OCEAN/EAST , FLIGHTS LAND FROM THE WEST/EVERGLADES.

I live in S. Palm beach county.

Storm w this is going to miss S.FL right?


Flights take off into the wind, and land into the wind. The prevailing winds just happen to be out of the east.
Member Since: October 30, 2007 Posts: 0 Comments: 270
sammywammybammy -- I don't think there is a specific overall wind speed that they use to close down flight operations at an airport. I would think that it isn't just about the planes themselves, but also about working conditions for the ground crew. Good question though, hope someone who knows will answer.
Member Since: May 19, 2009 Posts: 0 Comments: 250
If the NHC was really thinking 98L had the time to develop into a TD they would have given it a higher chance than 50% of developing. I agree that it looks impressive, but I just know how the NHC functions and they won't be classifying this system.
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Quoting sammywammybamy:
ARE THEY GOING TO CLOSE MIAMI INTERNATIONAL AIRPORT?

HOW WILL THIS CHANGE THE FLIGHT PLAN?


Uuuummm, call the airport!!!!
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I'm out. See you all at 5PM.
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Quoting MrJoeBlow:
I ain't on here much no more but I say this looks like it got Sarasota wrote all over it.


What's your reasoning?
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Quoting ecflweatherfan:
Just a guess... but possibly issuance of TS Watch northward along the FL East Coast to Fort Pierce or possibly as far north as Sebastian Inlet... and along the West FL coast up to Anclote Key (Including Tampa Bay) at 5pm??? Just thinking with the relocation and all...


Right it got Sarasota wrote all over it.
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Quoting StonedCrab:
I'm not seeing anything sustained enough to name this thing Bonnie yet...close, but no cigar.


are you blind? there are tons of sustained TS force winds being found by recon and they are all reliable
Member Since: March 10, 2010 Posts: 1 Comments: 7500
Quoting StormW:


Gonna resume a more WNW motion (280-285)


Oh...ok. I looked at the models and they are all centered in a LA lanfall. I'm assuming the track with shift more to the East as you presumed. Thanks for all your input!
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1233. leo305
Quoting Orcasystems:


AOI


wow
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Hunters found TS force winds at 39 mph at 591 feet.
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the hh this found 35kt winds
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Dead Sea? Btw worst vacation EVER!
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I'm not seeing anything sustained enough to name this thing Bonnie yet...close, but no cigar.
Member Since: October 30, 2007 Posts: 0 Comments: 270
Quoting Orcasystems:


Now now grasshopper... slow down :)


You know me "grumpy like an old man". But yes I kinda busted out there, don't usually do that. My apologies Taz.
Member Since: September 6, 2009 Posts: 2 Comments: 3712
I'm trying to think of a storm that covers the gulf in late july and stays a weak system as per models.
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Just a guess... but possibly issuance of TS Watch northward along the FL East Coast to Fort Pierce or possibly as far north as Sebastian Inlet... and along the West FL coast up to Anclote Key (Including Tampa Bay) at 5pm??? Just thinking with the relocation and all...
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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.