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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Quoting Jeff9641:
TD3 is almost moving NNW now at a dead aim for MIA to West Palm Beach. If this goes to the Keys it would have to start moving WNW right now as it continues to lift up the Bahama Chain.


remember all storms wooble
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Anyone have a google earth link with recon? I always loose it for some reason.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Is google earth working right?
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dammmm.looking like td4 at 5pm!!!!
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467. xcool
Link


est1986
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Quoting WxLogic:
Here's a SKEW-T from MYNN (Bahamas Int. Apt):



I have noted by the circle the SE component at Mid levels helping give TD3 take a more Northerly component to its movement (Which is also where the weakness is). I've also marked the dry air that is present to the W of TD3.


Nice obs
Member Since: October 28, 2006 Posts: 57 Comments: 30727
Quoting whs2012:
Local met said the stronger TD3 is the further south it goes, and the weaker it is the further north I goes? I thought it was the opposite. :/


That only works in some situations. I cannot explain it properly so I'll let someone else have the liberty to.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

THE GOVERNMENT OF THE BAHAMAS HAS ISSUED A TROPICAL STORM WARNING
FOR THE CENTRAL AND NORTHWESTERN BAHAMAS.

A TROPICAL STORM WARNING HAS BEEN ISSUED FOR THE FLORIDA EAST COAST
FROM GOLDEN BEACH SOUTHWARD INCLUDING THE ENTIRE FLORIDA KEYS AND
FLORIDA BAY...AND ALONG THE WEST COAST OF FLORIDA NORTHWARD TO
BONITA BEACH.

A TROPICAL STORM WATCH HAS BEEN ISSUED FOR THE EAST COAST OF FLORIDA
FROM NORTH OF GOLDEN BEACH TO JUPITER INLET INCLUDING LAKE
OKEECHOBEE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* CENTRAL AND NORTHWESTERN BAHAMAS
* FOR THE FLORIDA EAST COAST FROM GOLDEN BEACH SOUTHWARD INCLUDING
THE ENTIRE FLORIDA KEYS AND FLORIDA BAY...AND ALONG THE WEST COAST
OF FLORIDA NORTHWARD TO BONITA BEACH

A TROPICAL STORM WATCH IN IN EFFECT FOR...
* THE EAST COAST OF FLORIDA NORTH OF GOLDEN BEACH TO JUPITER INLET
INCLUDING LAKE OKEECHOBEE

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE
UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.
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Quoting Patrap:


Thats is the forecast dilemma


Hence the low confidence on the future of the system from the NHC once it enters the GOM.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Quoting staggalee:
Obviously, the models and NHC is counting on shear (or something) in the GOM to inhibit intensification. My question: are they counting on the shear from the ULL or something else. If the ULL moves faster than Bonnie, will the shear still be there to knock down Bonnie?
The shear is coming from the upper level low in front of TD 3.(The large U shaped area over florida atm. Depending on if it makes more space between itself and TD 3 or not is the problem...if it moves away..sheer and dry air will decrease..the opposite will stay the same, inhibiting strengthening.
Member Since: July 5, 2008 Posts: 0 Comments: 254
Quoting StormW:


Yes...and it's temporary.

Where I have the pink shading is the weakness.

img src="Photobucket" alt="" />

If you go here, look ahead of the system, and you can see it will pick back up to the WNW

vVIS LOOP


Thank you, StormW.
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Quoting staggalee:
Obviously, the models and NHC is counting on shear (or something) in the GOM to inhibit intensification. My question: are they counting on the shear from the ULL or something else. If the ULL moves faster than Bonnie, will the shear still be there to knock down Bonnie?


That is the forecast dilemma
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Quoting xcool:


12Z







Where are you getting these? They're to small for me to see on here and I can't click them to englarge it
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Obviously, the models and NHC is counting on shear (or something) in the GOM to inhibit intensification. My question: are they counting on the shear from the ULL or something else. If the ULL moves faster than Bonnie, will the shear still be there to knock down Bonnie?
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454. unf97
We will know much more of course once Recon arrives in the system in terms of strength and motion. But, if I was to hedge an educated guess for the moment based on what I am seeing now the system looks poised to track right through Dade county and the Everglades and emerge off the SW FL coast into the GOM during the weekend.
Member Since: September 25, 2007 Posts: 0 Comments: 1193


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Quoting MahFL:
"In Florida, crews removed booms intended to protect waterways in the Panhandle from oil. High winds and storm surge could carry the booms into sensitive wetlands."

That makes no scense, you'd think they'd leave them just incase they STOPPED some oil. What's worst booms or oil ?



Booms in 8-10 foot seas don't stop any oil, they just get destroyed and entangled into wetlands causing unnecessary damage. With this storm coming from the East this will actually push the oil away from the FL Panhandle as we'll start to see strong East winds over the next couple of days rotating around the center of the storm to our South.
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Here's a SKEW-T from MYNN (Bahamas Int. Apt):



I have noted by the circle the SE component at Mid levels helping give TD3 take a more Northerly component to its movement (Which is also where the weakness is). I've also marked the dry air that is present to the W of TD3.
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Hi StormW,
according to the NHC cone, TD3 should be closest to approach of Florida by 8 am tomorrow, any idea if that is still accurate? and will it clear out by midnight from FLL?
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The center looks to be reforming 100 miles north of NHC location
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Look at the right hand corner is that the center?
Link
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IF HH's measure max winds on the east how could it be possible that it doesn't include the forward motion. I don't think that it is. This has been an ongoing debate around here and causes a lot of confusion. From everyone I have asked this question to the answer is forward speed is already included(how could it not be) in the max winds.
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Per NWS Ruskin conference call...

Looks as if the storm will possibly get to a weak TS. As far as Florida's west coast, there is a chance for 1 - 3" of rain and isolated tornadoes Lee County south, with 1" of rain possible parts north.

A little bit of gust in the Tampa Bay area - 10 - 15 mph. Winds will be offshore, so no issues with rip currents or abnormally high tides.

Another conference call scheduled for tomorrow...
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Storm.....any thoughts on a timetable for landfall?? Not the 1st one....the second....
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Quoting MahFL:
"In Florida, crews removed booms intended to protect waterways in the Panhandle from oil. High winds and storm surge could carry the booms into sensitive wetlands."

That makes no scense, you'd think they'd leave them just incase they STOPPED some oil. What's worst booms or oil ?



Because there is no chance they will stop anything in high wind and waves. They are useless even with a heavy chop, never mind 10 ft seas.
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Quoting omgonozohshite:
Morning folks, TD3 hits pascagoula, MS as a category 3.



Link please!
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center my be getting exposed?
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Key west will get some rain and wind.
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438. xcool


98L
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12Z HWRF 30 hours


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Quoting scott39:
Will it get out of its way when it gets in the GOM?


Not sure.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Kori-based on your update, are you thinking a Lily(i) landfall?
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433. xcool


12Z





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dude!! freaking relax on the everything coming to Orlando thing.
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Quoting ElConando:
ULL is moving SW lowering shear but also bringing more dry air into the system.
Will it get out of its way when it gets in the GOM?
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hi guys, good afternoon :)

If the hwrf and gfdl models are right, making 98L stalling or moving really slow in a looplike form, we could face some SERIOUS flooding issues in Veracruz, South Tamaulipas, and the central eastern part of Mexico. Let's hope this doesn't happen.



At Monterrey, we are expecting around 75-150 mm of rain or between 3-6 in. Which would create very hazardous conditions regarding flashflood, mudslides and other problems related to traffic as the main highways at the city that run parallel to Santa Catarina river were severely damaged and in some parts dissapeared due to Alex.
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I have a question for any of the experts, or any other knowledgable figures on the blog currently. Is the ULL expected to either weaken, move faster than TD3, thus creating a more favorable environment for strengthning, or just not affect TD3 like it is currently doing once it gets into the GOM? In other word could this strenghten significantly once in the GOM?
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thanks for anwsering my question earlier,I'm starting to think if the center stays over water theirs going to be a cane in the SE GOM sat night!!!...sat night could be active along FL's west coast if it starts moving northerly...
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ULL is moving SW lowering shear but also bringing more dry air into the system.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
Storm thank you for your update, as usual it is most appreciated. It appears that TD3 is pulling in moisture from the SSW and closing the center of circulation. The movement N of WNW is troubling to those of us who live in Miami and SE Florida.
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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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