Tropical depression forming over the Bahamas

By: Dr. Jeff Masters , 1:29 PM GMT on July 22, 2010

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A tropical wave (Invest 97L) over the eastern Bahama Islands has developed a closed circulation at the surface, and has become a tropical depression or tropical storm. Here is the text of the Special Tropical Weather Outlook from NHC at 8:25am EDT today:

Visible satellite images and observations from the Bahamas indicate that the area of low pressure in the southeastern Bahamas has become better organized and a closed circulation has formed. Advisories on a tropical depression or a tropical storm will be initiated at 11 am EDT...1500 UTC today. This advisory will likely include tropical storm watches and warnings for portions of the Bahamas and southern Florida.

Satellite images of 97L show a modest area of heavy thunderstorms that have slowly increased in intensity and areal coverage this morning. Water vapor satellite loops show a large area of dry air lies to the west of 97L, over Florida. This dry air is associated with a large upper-level low pressure system that is moving west at about the same speed 97L is. The counter-clockwise flow of air around the upper low is bringing about 20 knots of wind shear to 97L. Surface observations in the Bahamas and several nearby ships have shown top winds in 97L 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 97L
The storm is in a fairly straightforward steering current environment, and 97L 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 97L over the next two days. The location of 97L'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 97L
The primary detriment to development of 97L 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 97L, it will bring wind shear of about 20 knots and dry air into the storm. This will limit the intensification potential of 97L to no more than about 10 - 20 mph per day. If the upper-level low picks up speed and pulls away from 97L, the storm may be able to intensify at a faster rate. None of the computer models is calling for that to happen, but it is possible. I put the odds of 97L 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.

I'll have an update after NHC releases their 11am advisory package.

Jeff Masters

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Good morning all!
I've been lurking and learning here for awhile .... I should have known something was coming this way, I teach college and our summer finals are Monday and Tuesday, lucky students, they might have more time to study. JOY!
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98L in the BOC should be classified as a TD as well. The organization of the system has continued to improve since the early morning hours.
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Actually this will be a good storm for Central and South Florida... we REALLY need the rain right now!!! The water table is low enough right now to handle 6" of rain efficiently, with only minor temporary ponding.
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Quoting CybrTeddy:
I hold low confidence with the models, none of which truly ever developed TD3.

cyber, both the GFDL and HWRF developed this storm and have constant in doing so for 3 days.
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I kinda doubt that, (or at least not significantly) due to the ridge to it's north. But time will tell.
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614. 7544
all the stroms are to the north the heavy ones will effect dade and broward and wpb will get the stronger rains and stroms right
Member Since: May 6, 2007 Posts: 0 Comments: 6618
Seems like they are moving this too fast IMO.. Fri PM. S.W. of Naples????
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Quoting MiamiHurricanes09:
Max Mayfield stating that 97L will not be able to go anywhere north of southern Florida because of a ridge to the north regardless of how strong it is.


Yup it's going through the Keys with prospects of a minimal TS. If it stays this tiny, N Miami might see clouds, scattered showers, and a breeze of 15-20.
Member Since: July 26, 2003 Posts: 3 Comments: 428
Quoting MiamiHurricanes09:
Max Mayfield stating that 97L will not be able to go anywhere north of southern Florida because of a ridge to the north regardless of how strong it is.

Hurricane, dont you remember? he said that abotu Irene i wont stop watching.J.I.C.
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Quoting CaneHunter031472:


What you mean, as a Tropical Storm? I believe that what's not good at all are the chances of it becoming a Hurricane 15% tops, but if you refer to a tropical storm maybe even a strong one, yes you could be right not good at all, not only for Texas, but for Louisiana and Mississippi because it will push that dogone oil ashore.


I was talking about the oil part.
Member Since: September 2, 2006 Posts: 110 Comments: 6814
Quoting weatherskink:
They're calling it a depression , but I wouldn't be surprised if the next flight shows otherwise .

I have a feeling from the following they think otherwise.

TROPICAL DEPRESSION THREE DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032010
1100 AM EDT THU JUL 22 2010

THE TROPICAL WAVE/DISTURBANCE THAT NHC HAS BEEN TRACKING FOR THE
PAST SEVERAL DAYS ACROSS THE ATLANTIC HAS DEVELOPED A SURFACE
CIRCULATION AND ENOUGH ORGANIZED CONVECTION TO BE CLASSIFIED AS A
TROPICAL DEPRESSION. THE DEPRESSION IS SHEARED AT THIS TIME AND ITS
CENTER IS LOCATED ON THE SOUTHWEST SIDE OF A CYCLONICALLY CURVED
CONVECTIVE BAND. THE SHEAR APPEARS TO BE RELAXING A
LITTLE...HOWEVER...AS INDICATED BY THE MOTION OF THE HIGH CLOUDS ON
HIGH RESOLUTION IMAGES. THE CYCLONE IS STILL INTERACTING WITH A
STRONG WESTWARD-MOVING UPPER LOW TO THE WEST. THIS PATTERN WOULD
ONLY ALLOW THE DEPRESSION TO STRENGTHEN A LITTLE AS INDICATED IN
THE OFFICIAL FORECAST...BUT THIS FORECAST IS UNCERTAIN. IN FACT...
NONE OF THE MODELS SHOW SIGNIFICANT INTENSIFICATION.

BECAUSE THE CENTER JUST FORMED...THE INITIAL MOTION IS UNCERTAIN.
THE BEST ESTIMATE IS TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 13
KNOTS. GLOBAL MODELS FORECAST A WELL-ESTABLISHED SUBTROPICAL RIDGE
EXTENDING FROM THE ATLANTIC WESTWARD ACROSS THE SOUTHERN UNITED
STATES. THIS STEERING PATTERN SHOULD KEEP THE CYCLONE ON A GENERAL
WEST-NORTHWESTWARD TRACK THROUGH 3 TO 4 DAYS ACROSS THE FLORIDA
STRAITS AND THE KEYS AND THEN INTO THE GULF OF MEXICO. BECAUSE THE
RIDGE IS FORECAST TO STRENGTHEN...THE CYCLONE SHOULD BEGIN TO
INCREASE ITS FORWARD SPEED. THE TRACK GUIDANCE IS TIGHTLY CLUSTERED
THROUGH 4 OR 5 DAYS...ALTHOUGH SOME MODELS WEAKEN THE CYCLONE
EARLIER.

AN AIR FORCE PLANE WILL BE IN THE AREA THIS AFTERNOON AND WILL HELP
TO DETERMINE IF THE SYSTEM HAS BECOME A TROPICAL STORM.


FORECAST POSITIONS AND MAX WINDS

INITIAL 22/1500Z 21.9N 75.0W 30 KT
12HR VT 23/0000Z 22.6N 76.8W 35 KT
24HR VT 23/1200Z 23.8N 80.0W 40 KT
36HR VT 24/0000Z 25.0N 83.2W 40 KT
48HR VT 24/1200Z 26.0N 86.5W 40 KT
72HR VT 25/1200Z 28.0N 91.5W 45 KT
96HR VT 26/1200Z 31.0N 94.0W 25 KT...INLAND
120HR VT 27/1200Z 33.0N 95.0W 20 KT...POST-TROP/REMNT LOW


$$
FORECASTER AVILA/ROBERTS
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I hold low confidence with the models, none of which truly ever developed TD3.
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Exactly, look at where the convection is bulging out to and that is the current and projected path

Quoting Jeff9641:
Track will shift north at 5pm due to it's continued northwestward build. Look at the visible sat and zoom in and you will see what I'm talking about.
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Quoting Jeff9641:
Track will shift north at 5pm due to it's continued northwestward build. Look at the visible sat and zoom in and you will see what I'm talking about.


You really don't get it do you. There is a strong ridge in place that will keep this storm from going North. You are the only one here "trying" to forecast a Northward motion
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Quoting Jeff9641:


Good morning!


good morning to you too :)
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Recon will certainly get a more accurate fix.
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At this rate of speed assuming present course it will be in Key Largo in 27 hours.
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I dont like WU's track map on this one. it has it coming in around Freeport, Tx area
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I think the cone should shift a bit northward at 5PM.

Member Since: September 2, 2009 Posts: 130 Comments: 21032


Only a TS in the GOM???
Member Since: September 2, 2006 Posts: 110 Comments: 6814
594. xcool
td 65 imo imo
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"STORM SURGE...STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 1 TO
2 FEET ABOVE GROUND LEVEL OVER PORTIONS OF THE BAHAMAS AND THE
FLORIDA KEYS."

A 1 ft to 2 ft storm surge will have no real effect on East or South Florida coast or in the Bahamas.

However, a 1-2 ft storm surge can be a disaster when it crosses the oil spill in the Gulf. That can carry the oil a mile or more into coastal marsh land or push oil into the bays.

Even though strength potential may be limited, the path is a worst-case for oil spill cleanup efforts.
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Member Since: August 9, 2009 Posts: 10 Comments: 4504
Quoting tropicfreak:


Not good, not good at all.


What you mean, as a Tropical Storm? I believe that what's not good at all are the chances of it becoming a Hurricane 15% tops, but if you refer to a tropical storm maybe even a strong one, yes you could be right not good at all, not only for Texas, but for Louisiana and Mississippi because it will push that dogone oil ashore.
Member Since: August 1, 2007 Posts: 0 Comments: 163
When they say "east coast" of FL, they mean just the coast, not inland. Just to clear this up for some who may not know.
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Quoting ElConando:


TD 3 now. Learn some manners I think its earned it :P.
LOL.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
588. 7544
yep the plane will find a ts
Member Since: May 6, 2007 Posts: 0 Comments: 6618
587. MahFL
75 seems wrong to me too.
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Well folks, we are nearing the end of july, just when things really get busy. This is just the beginning.
Member Since: September 2, 2006 Posts: 110 Comments: 6814
I saw that ridge yesterday, and was wondering if it was going to drive TD3 west into Central Gulf or even NW Gulf
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Quoting MiamiHurricanes09:
Max Mayfield stating that 97L will not be able to go anywhere north of southern Florida because of a ridge to the north regardless of how strong it is.


TD 3 now. Learn some manners I think its earned it :P.
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Umm 50 mph? that's it? Come on NHC, look at those water temps and also take note the ULL is moving further away. I think TD3 will surprise you guys more then us later today.
Member Since: July 1, 2008 Posts: 13 Comments: 7334
Has anyone seen this yet??


000
WTNT43 KNHC 221503
TCDAT3
TROPICAL DEPRESSION THREE DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032010
1100 AM EDT THU JUL 22 2010

THE TROPICAL WAVE/DISTURBANCE THAT NHC HAS BEEN TRACKING FOR THE
PAST SEVERAL DAYS ACROSS THE ATLANTIC HAS DEVELOPED A SURFACE
CIRCULATION AND ENOUGH ORGANIZED CONVECTION TO BE CLASSIFIED AS A
TROPICAL DEPRESSION. THE DEPRESSION IS SHEARED AT THIS TIME AND ITS
CENTER IS LOCATED ON THE SOUTHWEST SIDE OF A CYCLONICALLY CURVED
CONVECTIVE BAND. THE SHEAR APPEARS TO BE RELAXING A
LITTLE...HOWEVER...AS INDICATED BY THE MOTION OF THE HIGH CLOUDS ON
HIGH RESOLUTION IMAGES. THE CYCLONE IS STILL INTERACTING WITH A
STRONG WESTWARD-MOVING UPPER LOW TO THE WEST. THIS PATTERN WOULD
ONLY ALLOW THE DEPRESSION TO STRENGTHEN A LITTLE AS INDICATED IN
THE OFFICIAL FORECAST...BUT THIS FORECAST IS UNCERTAIN. IN FACT...
NONE OF THE MODELS SHOW SIGNIFICANT INTENSIFICATION.

BECAUSE THE CENTER JUST FORMED...THE INITIAL MOTION IS UNCERTAIN.
THE BEST ESTIMATE IS TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 13
KNOTS. GLOBAL MODELS FORECAST A WELL-ESTABLISHED SUBTROPICAL RIDGE
EXTENDING FROM THE ATLANTIC WESTWARD ACROSS THE SOUTHERN UNITED
STATES. THIS STEERING PATTERN SHOULD KEEP THE CYCLONE ON A GENERAL
WEST-NORTHWESTWARD TRACK THROUGH 3 TO 4 DAYS ACROSS THE FLORIDA
STRAITS AND THE KEYS AND THEN INTO THE GULF OF MEXICO. BECAUSE THE
RIDGE IS FORECAST TO STRENGTHEN...THE CYCLONE SHOULD BEGIN TO
INCREASE ITS FORWARD SPEED. THE TRACK GUIDANCE IS TIGHTLY CLUSTERED
THROUGH 4 OR 5 DAYS...ALTHOUGH SOME MODELS WEAKEN THE CYCLONE
EARLIER.

AN AIR FORCE PLANE WILL BE IN THE AREA THIS AFTERNOON AND WILL HELP
TO DETERMINE IF THE SYSTEM HAS BECOME A TROPICAL STORM.


FORECAST POSITIONS AND MAX WINDS

INITIAL 22/1500Z 21.9N 75.0W 30 KT
12HR VT 23/0000Z 22.6N 76.8W 35 KT
24HR VT 23/1200Z 23.8N 80.0W 40 KT
36HR VT 24/0000Z 25.0N 83.2W 40 KT
48HR VT 24/1200Z 26.0N 86.5W 40 KT
72HR VT 25/1200Z 28.0N 91.5W 45 KT
96HR VT 26/1200Z 31.0N 94.0W 25 KT...INLAND
120HR VT 27/1200Z 33.0N 95.0W 20 KT...POST-TROP/REMNT LOW

$$
FORECASTER AVILA/ROBERTS
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The NHC does say there is low confidence in this forecast.
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Quoting HarleyStormDude52:
548. bohonkweatherman 3:05 PM GMT on July 22, 2010
Accuweather says it has been a depression for some time now, TD3 should become a storm and possible cat1 hurricane before its final landing in Louisiana or Texas next week? Right now sheer is keeping it from being a stronger storm.



I was thinking far east tx coast to eastern la earlier but I got hammered!!!!!!!!!!! time will tell

12 percent chance of it becomeing a hurricane before landfall in the gulf as per the NHC
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Quoting CybrTeddy:
Developing TD in BOC..


Looks very organized.
Member Since: September 2, 2006 Posts: 110 Comments: 6814
since the models are suspect at showing intensity levels much above a 3...we can conclude they will also perhaps not understand that if the current anticylone above helps this thing generate to a hurricane...what would prevent it from following this developing storm...as it slips through the Fl straits....and hanging with it if it explodes into a major hurricane..which they can do inside of 48 hours??
Member Since: June 30, 2010 Posts: 0 Comments: 27
They said the Upper level low over Florida is producing strong sheer over TD3 and this may continue for awhile? The Upper low is moving west southwest though and could move away from what will soon be Bonnie. This according to Accuweather.
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Quoting CybrTeddy:
Can't find any data from recon..


Neither can I. No data from recon on Google Earth.
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Quoting LdyAvalon:
Been lurker here since '04 and have posted a few times. Always come here for accurate information. I'm in Clearwater. Is it safe to say we are not going to see much from this? Looks like there would have to be a major shift. TIA!

rain.
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548. bohonkweatherman 3:05 PM GMT on July 22, 2010
Accuweather says it has been a depression for some time now, TD3 should become a storm and possible cat1 hurricane before its final landing in Louisiana or Texas next week? Right now sheer is keeping it from being a stronger storm.



I was thinking far east tx coast to eastern la earlier but I got hammered!!!!!!!!!!! time will tell
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Max Mayfield stating that 97L will not be able to go anywhere north of southern Florida because of a ridge to the north regardless of how strong it is.
Member Since: September 2, 2009 Posts: 130 Comments: 21032

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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.