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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Looking at post# 644... One thing standing out to me is the HWRF model and its track... almost spot-on as to its current location.
Member Since: Posts: Comments:
Quoting MahFL:
The HH should be on site at midday EDT, or 1 hour either side, as I can never work it out with 100 % confidence.

so the 2pm advisory is the more accurate one
Member Since: July 21, 2010 Posts: 0 Comments: 1118
668. xcool
f5 f5f5f5f5f5 omg
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Hmmm.... still no update?
Member Since: October 25, 2005 Posts: 19 Comments: 21879
Quoting tropicfreak:


They just don't want to scare the crap out of everyone on the gulf coast.

i dont think so. You know people live on that big penisula and island between you and bonnie right? lol The gulf is not always their center of their attention.
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Quoting FLdewey:


Once again Reed I think you should drive down there, rip the director out of his chair and take the place over.


Doc thinks it is possible...per update "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%"
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Looking atthis loop, it appears there is burst of convection directly over the center.
Member Since: June 29, 2009 Posts: 13 Comments: 5311
Quoting ho77yw00d:


good morning to you too :)

Good morning Hollywood. Deerfield Beach here. What are you thinking about this?
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Quoting 7544:
cone will go north on the next update from the keys to miami
Doubt it, just a small shift to the right is what I'm expecting at 5PM, not that far north though.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting StadiumEffect:
The center it to the south-west side of the heavy convection. The circulation is pulling in moisture from the north/north-east and attempting to close off the western side, giving it the appearance of a northward component. Don't pay attention to the convection, pay attention the the center itself.


Thank you Stadium.....I believe he is the one that needs to get his facts straight. But then again everyone is allowed to have their own observation.
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hope im hungry because I'm eating crow for breakfast. :)
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Quoting 7544:
cone will go north on the next update from the keys to miami


may u atleast explain why u feel that way
Member Since: July 21, 2010 Posts: 0 Comments: 1118
Quoting swlagirl:
From the 5 day cone it looks like TD3 will pass right over my house...I wonder how much the track will change in the next few days?! I never count on the 5 day cone being correct.


Smart thinking, it could change a lot.....
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654. MahFL
The HH should be on site at midday EDT, or 1 hour either side, as I can never work it out with 100 % confidence.
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Quoting AllStar17:
I think this first advisory is very suspect.

Center at 75.0 W? Don't think so.
Only 50 mph in GOM? Don't think so.
Expected to increase in forward speed from 15 mph? Don't know about that, either.
The increase in forward speed I agree with. The forecast as far as strength goes I disagree with. I think there will be a hurricane at some point.
Member Since: September 27, 2007 Posts: 1 Comments: 20935
74.5 22.0 nice band about to wrap in on the N.W. Quad.
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Quoting tropicfreak:


40mph winds have been reported in the Bahamas.
1) Where? 2) By whom? 3) Sustained or gusts?

Quoting PensacolaDoug:


I'm under the impression that the Bahamas are not much more than speed bumps.
THIS is SO INSULTING!!!!! I'm reporting you to Admin right now!!!!

We're not SPEED BUMPS!!! We're sand dunes!!!

[much higher than speed bumps]

But SERIOUSLY.....

LOL the highest point in The Bahamas is only a little over 200 feet above sea level, and most islands average about 50 feet. Plus many are very narrow; New Providence is 21 miles long, but only 7 miles wide (and shaped like an eye).

So there really isn't much there to disrupt a storm... a bigger problem is a slow moving storm running out of fuel over one of the Bahama Banks....

Member Since: October 25, 2005 Posts: 19 Comments: 21879
Quoting CybrTeddy:
Can't find any data from recon..



Are they already there? Don't it take a while ? I don't know so that is why I am asking.
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Quoting FLdewey:


Once again Reed I think you should drive down there, rip the director out of his chair and take the place over.
Not a good idea. Taz will report him before he gets out of the driveway.
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647. 7544
cone will go north on the next update from the keys to miami
Member Since: May 6, 2007 Posts: 0 Comments: 6749
646. 900MB
Quoting reedzone:
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.


Reed- I don't understand the NHC reasoning here! Aside from moderate shear and moderate dry air (very moderate at this point), given the path and SSTs I am not understanding the logic here.
If this ends up near 50kts running into the Gulf, I would expect at least a Cat1.
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Recon enroute.

000
URNT15 KNHC 221511
AF306 02BBA INVEST HDOB 06 20100722
150230 2829N 08818W 3995 07656 0464 -160 //// 059017 018 /// /// 05
150300 2828N 08816W 3997 07652 0463 -160 //// 060018 018 /// /// 05
150330 2827N 08814W 3995 07656 0463 -162 //// 061017 018 /// /// 05
150400 2826N 08811W 3994 07657 0463 -164 -208 064016 017 /// /// 03
150430 2825N 08808W 3995 07656 0463 -165 -214 062015 016 /// /// 03
150500 2824N 08806W 3995 07655 0462 -165 -218 062015 016 /// /// 03
150530 2823N 08803W 3994 07656 0461 -165 -222 059015 015 /// /// 03
150600 2822N 08801W 3995 07653 0461 -165 -225 056015 015 /// /// 03
150630 2822N 08758W 3994 07656 0462 -161 -228 054015 015 /// /// 03
150700 2821N 08755W 3994 07655 0461 -160 -230 051014 015 /// /// 03
150730 2820N 08753W 3995 07652 0461 -160 -232 050015 015 /// /// 03
150800 2819N 08750W 3995 07652 0459 -160 -233 052016 016 /// /// 03
150830 2819N 08747W 3995 07650 0458 -160 -234 055015 016 /// /// 03
150900 2818N 08745W 3994 07653 0458 -160 -235 055014 015 /// /// 03
150930 2817N 08742W 3995 07651 0458 -160 -236 056013 013 /// /// 03
151000 2816N 08740W 3995 07653 0459 -160 -237 059015 015 /// /// 03
151030 2816N 08737W 3995 07652 0459 -160 -238 059015 015 /// /// 03
151100 2815N 08734W 3994 07652 0457 -163 -239 060014 014 /// /// 03
151130 2814N 08732W 3996 07645 0456 -160 -240 057014 014 /// /// 03
151200 2813N 08729W 3992 07652 0455 -162 -241 054014 015 /// /// 03
$$
;

Member Since: September 2, 2009 Posts: 130 Comments: 21109
Member Since: January 24, 2010 Posts: 0 Comments: 529
From the 5 day cone it looks like TD3 will pass right over my house...I wonder how much the track will change in the next few days?! I never count on the 5 day cone being correct.
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Quoting AllStar17:
I think this first advisory is very suspect.

Center at 75.0 W? Don't think so.
Only 50 mph in GOM? Don't think so.
Expected to increase in forward speed from 15 mph? Don't know about that, either.
Yep, the cone also seems a little too narrow and south to me.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
I still have no hurricane hunter information.
Member Since: June 29, 2009 Posts: 13 Comments: 5311
Quoting Waltanater:
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.
I'm not sure that your clearing up of things is correct. I think you're wrong and I am...confused.
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Quoting Jeff9641:


Get your facts straight.. I called it last night along with others and again this morning. It is building to where the best convection and vorticty lies once this is established then a wnw motion will insue.
Max Mayfield made mention that the ridge will prevent it from going north of s fl and the nhc track reinforces those statements. But you never know. Time will tell.
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635. IKE
Miami....you're not in the cone....

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Quoting superweatherman:
they not even update the 98L... not recon to that one...?

This is a special update, Normal update will be 2pm for 98L
Member Since: September 30, 2007 Posts: 9 Comments: 15935
Quoting reedzone:
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.


They just don't want to scare the crap out of everyone on the gulf coast.
Member Since: September 2, 2006 Posts: 110 Comments: 6874
I think this first advisory is very suspect.

Center at 75.0 W? Don't think so.
Only 50 mph in GOM? Don't think so.
Expected to increase in forward speed from 15 mph? Don't know about that, either.
Member Since: June 29, 2009 Posts: 13 Comments: 5311
href="http://www.nhc.noaa.gov/refresh/graphics_at3 shtml/145913.shtml?5-daynl#contents" target="_blank">Link
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Member Since: September 2, 2007 Posts: 178 Comments: 20439
Let me be the first to say that every news channel from now till early next week will be talking about the Bonnie and Deepwater collision about to occur. "Breaking News".....Bonnie to disperse oil to....who knows....but the new track sure sucks for that
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Quoting Drakoen:
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.


I doubt they'll classify it.
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626. jpsb
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!
Hi Tia, jim in San Leon.
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Is there anything to limit intesification, once the ULL gets it's bum out of the way??
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Quoting bjdsrq:


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.
I'm thinking that the center will go over the keys, but the worst weather appears to be north of the center.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting Jeff9641:
The center is continuing to build north. look at the visible below. IMAO......


http://www.wunderground.com/tropical/tracking/at201097_sat.html
The center it to the south-west side of the heavy convection. The circulation is pulling in moisture from the north/north-east and attempting to close off the western side, giving it the appearance of a northward component. Don't pay attention to the convection, pay attention the the center itself.
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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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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.