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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322. Bonz
Quoting 69Viking:


We'll know for sure whenever the Hurricane Hunter flight gets out there today. I'm kind of surprised they waited so long with it's proximity to South Florida and some major populations that need to know the facts of what could be on their doorstep by tomorrow!


Most are at work and wouldn't know 'til the local news comes on at 6 tonight anyhow.
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Quoting Seamule1:


well...it will be :)
You have any facts to back up this nonsense? It isn't even a minor yet and your talking major. What a joke
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Quoting Drakoen:
Latest recon position

25.850N 79.800W


Just so people don't freak out he means the HH plane.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting stormhunter23:


Yeah, I know but most of the flights I been tracking have been passing over TD 3.


Got it, well enjoy your flight anyways.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
What happened to the recon flight?
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Latest recon position

25.850N 79.800W
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Quoting StadiumEffect:
TS force winds in gusts, not sustained.
I've seen some observations with winds not gusts of 40mph.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
winds on the south side r only 5 to 10 mph go miles north and its like 35 to 45 what a diffrence a few miles can make
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Quoting Drakoen:
Looks like it is moving between WNW and NW at the present hour.


I've been noticing that as well. Drak, I wanted to get your opinion on my forecast for this storm in post 221.
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Quoting Baybuddy:


On some channels, the forecast can be the Advertisers opinion: Home Depot...Lowes..Generac etal.


LOL that's probably true!
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I realize this comment is not directly related to TD#3 so i apologize in advance!
If any of you have an IPhone, can you recommend a good app for tracking tropical weather?
Thanks!!
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310. xcool
rmbjoe1954 PAGES 6
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting ElConando:


We shall see MH. Take a deep breath and wait. This ain't no Major were talking about here.


well...it will be :)
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Quoting ElConando:
276. You know they can change the flight pattern?


Yeah, I know but most of the flights I been tracking have been passing over TD 3.
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Quoting xcool:


BAD NEWS



Why did you say bad news? What is your reasoning?
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Quoting ElConando:


We shall see MH. Take a deep breath and wait. This ain't no Major were talking about here.
*Inhales -- Exhales* LOL.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting MiamiHurricanes09:
Looking at satellite the NHC is wrong on the location of the COC, I also highly doubt that it is moving at 15mph. The strength they are giving also seems too low, several surface observations across the Bahamas suggest TS force winds.


We'll know for sure whenever the Hurricane Hunter flight gets out there today. I'm kind of surprised they waited so long with it's proximity to South Florida and some major populations that need to know the facts of what could be on their doorstep by tomorrow!
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Quoting Drakoen:
Looks like it is moving between WNW and NW at the present hour.


CIMMS just updated, seems like the weakness N of the Bahamas opened up a little more.
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Quoting MiamiHurricanes09:
Looking at satellite the NHC is wrong on the location of the COC, I also highly doubt that it is moving at 15mph. The strength they are giving also seems too low, several surface observations across the Bahamas suggest TS force winds.
TS force winds in gusts, not sustained.
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Quoting MiamiHurricanes09:
Looking at satellite the NHC is wrong on the location of the COC, I also highly doubt that it is moving at 15mph. The strength they are giving also seems too low, several surface observations across the Bahamas suggest TS force winds.


We shall see MH. Take a deep breath and wait. This ain't no Major were talking about here.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting xcool:
Snowlover123


NOT YET


WIND SHEAR 10K


Yes, but when it becomes 0 K an anticyclone has formed, and right now it is forming one.
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Looks like it is moving between WNW and NW at the present hour.
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----- Current Analysis -----
Date : 22 JUL 2010 Time : 154500 UTC
Lat : 21:57:53 N Lon : 75:08:38 W


CI# /Pressure/ Vmax
2.2 /1007.4mb/ 32.0kt


Final T# Adj T# Raw T#
2.2 2.4 3.2

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : +16.3C Cloud Region Temp : -9.3C

Scene Type : SHEAR (0.18^ TO DG)

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : 0.2T/hour
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

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Quoting 69Viking:


But a forecast can be a forecaster's opinion of the weather data he has available or somethign like that LOL!



On some channels, the forecast can be the Advertisers opinion: Home Depot...Lowes..Generac etal.
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Gulf Coast Oil Bath Track...

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Quoting Snowlover123:


Have a safe flight! Tell us how it went! :)


Thanks, sure will!
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294. xcool
MScasinojunkie 15MIN FROM Lake
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting louisianaboy444:


Really? I don't see it
Looking at satelliteit seems like the NHC is wrong on the location of the COC, I also highly doubt that it is moving at 15mph. The strength they are giving also seems too low, several surface observations across the Bahamas suggest TS force winds.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
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269. Brain? you mean Brian?
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Convection is consolodating near the center, as the upper level winds continue to die down...

Quoting btwntx08:
REPOST:
sry but i want to do a poll on 98L,what precentange # will it be

A. 60%
B.70%
C.80%+


B. 70%.
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287. xcool
Snowlover123


NOT YET


WIND SHEAR 10K
Member Since: September 26, 2009 Posts: 2 Comments: 15684
261-Dont think this has been asked yet?
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Quoting MScasinojunkie:


exactly - and I don't think they've finished installing the booms along Bay St. Louis and Biloxi Bay! I live up in the Kiln, and storm surge could funnel the oil up into the Jourdan River in my neck of the woods - not good at all!


Boom will more than likely be removed prior to any storm surge.
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276. You know they can change the flight pattern?
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting stormhunter23:
hey im going to pass over TD3 tonight , is going to be one shaky flight for me.


That's my route for tonight



TD 3


Have a safe flight! Tell us how it went! :)
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Quoting FLdewey:


A forecast is based on data and does not factor in the forecasters location when forecasting a path.
An opinion is based on data and does not factor in the opiner location when opining
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For Miami Thurs Night and Friday morning and afternoon.

Tonight
Partly cloudy with scattered showers and isolated thunderstorms in the evening...then mostly cloudy with numerous showers and scattered thunderstorms. Windy. Some thunderstorms may produce gusty winds...tornadoes and heavy rainfall especially after midnight. Lows in the lower 80s. Northeast winds 15 to 20 mph becoming 20 to 25 mph. Chance of rain 60 percent.
rain
Friday
Mostly cloudy. Numerous showers and scattered thunderstorms. Windy. Some thunderstorms may produce gusty winds... tornadoes and heavy rainfall. Highs in the upper 80s. Southeast winds 20 to 25 mph with gusts to around 45 mph. Chance of rain 60 percent.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting xcool:
MScasinojunkie .I STAY IN Slidell :((((


dang - hope you dont live near the Lake!!
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Looking forward to those bands a little bit, FLdewey... the East Coast sure has been dry this summer (due to that persistant easterly wind flow for the past several weeks). My grass is brown here in Merritt Is.
Member Since: March 19, 2010 Posts: 0 Comments: 1147
hey im going to pass over TD3 tonight , is going to be one shaky flight for me.


That's my route for tonight



TD 3
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Quoting xcool:


BAD NEWS


So, the storm is developing an anticyclone?
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Interesting to say the least


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any word on any weather channel celebrities coming down here
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Worth Repeating

Please be careful with the hyperbole and misstatements of information.

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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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