Disturbance 94L in Central Atlantic; NHC management changes

By: Dr. Jeff Masters , 1:58 PM GMT on August 28, 2007

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A tropical wave midway between Africa and the Lesser Antilles (labeled "invest 94L" by NHC this morning) has become a little better organized this morning, and does have the potential to develop into a tropical depression later this week. Wind shear is a favorable 5-10 knots over 94L, and shear should not be a problem for it over the next few days. The system is not well-organized, with a sloppy, elongated circulation, as seen on last night's QuikSCAT pass. This morning's QuikSCAT pass missed the storm. The system does have a major impediment to development--the presence of a large, dusty area of dry air surrounding its north side (Figure 1). Water vapor satellite loops of the region don't show any significant moistening of the region around 94L occurring, and this will have to happen before the system can develop into a tropical depression. If the storm can develop a better-organized circulation, it will be able to pump more moisture into the surrounding atmosphere and help itself out. Current visible satellite loops shows that this is not happening at present--the thunderstorm activity associated with 94L is rather weak.

None of the reliable computer models develop 94L. The system should track through the Lesser Antilles Islands on Friday, bringing gusty winds and heavy rain. I expect that the earliest 94L could become a tropical depression would be Thursday, and it is unlikely the Lesser Antilles would experience anything worse than a 50 mph tropical storm. It is more likely that 94L will still be a tropical disturbance when it passes through the Lesser Antilles.


Figure 1. Water vapor satellite image of the Central Atlantic from 8:15am EDT 8/28/07. The brown colors denote very dry and dusty air from the Saharan Desert.

Honduras disturbance
A westward-moving tropical wave is bringing heavy rains to Honduras and Nicaragua today. Due to its close proximity to land, development of this wave into a tropical depression is not expected. The wave is under 10-15 knots of wind shear. None of the reliable models are predicting that this system will develop.

Computer model update
The UKMET and GFS models are indicating the possible development of a tropical depression by Thursday or Friday off the coast of Africa. There is a large surge of moisture with at least one strong tropical wave embedded in it coming off the coast of Africa this week. This moister air should make a more favorable environment for a tropical depression to form in than the one 94L finds itself in.

Most of the models also predict a low pressure system will develop off the North Carolina coast along an old frontal boundary on Thursday. Such a development may be an ordinary extratropical low pressure system, but could make the transition to a tropical system if the shear drops low enough.

NHC management changes
Acting director Dr. Ed Rappaport of The National Hurricane Center (NHC) will continue on the job until the end of this hurricane season, NOAA management revealed yesterday. Rappaport replaced director Bill Proenza on July 9, following an extraordinary few months of tumult at NHC. Joining the NHC staff on September 4 will be a new interim deputy director--Bill Read, who currently serves as the meteorologist in charge of the National Weather Service's Houston-Galveston office. Deputy director was the post Rappaport held prior to July 9. Bill Read applied for the directorship of NHC when Max Mayfield retired, but was not awarded the job. His arrival at NHC during the peak of hurricane season will be a welcome addition, as he has considerable experience dealing with hurricane emergencies.

In an apparent effort to follow some of the management changes recommended by the independent review team that performed the snap inspection of NHC in early July (see Attachment 9 of the Senate testimony from July), a new manager of the ten hurricane forecasters has been appointed as well. Rick Knabb, who is one of the six senior hurricane specialists, will be the new manager, and will be Rappaport's backup for TV interviews during hurricane emergencies.

It is still undecided where former director Proenza will wind up, but the chairs of two Senate subcommittees investigating the matter have recommended that Proenza be returned to his former job as head the NWS Southern Region.

Next update
Tomorrow is the 2-year anniversary of Hurricane Katrina. I'll discuss my experience with blogging about the storm, and give an update on 94L and the rest of the tropics.

Jeff Masters

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593. extreme236
9:28 PM GMT on August 28, 2007
Posted By: nash28 at 9:26 PM GMT on August 28, 2007.

My God! Let the thing grow! It takes time! I can't remember the last storm that went from open wave to TS or Hurricane in less than 12hrs.


Amy is just not happy that something may stop her prediction from being true.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
591. nash28
9:25 PM GMT on August 28, 2007
My God! Let the thing grow! It takes time! I can't remember the last storm that went from open wave to TS or Hurricane in less than 12hrs.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
590. weatherbrat
9:24 PM GMT on August 28, 2007
Hey Nash,

94L...what do you think. Favorable for slow development within the next 48 hours? I think a more northerly track as the BAMS 1800Z is showing. What's your opinion?
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589. HurricaneMyles
9:26 PM GMT on August 28, 2007
Hey, Amystery, can you please modify your comment and unstretch the blog. It'd be nice of ya.
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588. extreme236
9:26 PM GMT on August 28, 2007
Amy where did they say it was disorganized and it wont develop? please bold that spot
Member Since: August 2, 2007 Posts: 19 Comments: 19234
587. extreme236
9:26 PM GMT on August 28, 2007
Amy apparently doesnt realize that the pressure has dropped 2mb, the system has a circulation, and winds are at TD strength. Finally, something that may shut Amy up about her no development guess
Member Since: August 2, 2007 Posts: 19 Comments: 19234
584. Bobbyweather
5:21 PM EDT on August 28, 2007
SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE LOCATED ABOUT MIDWAY BETWEEN AFRICA AND THE LESSER ANTILLES HAVE NOT BECOME ANY BETTER ORGANIZED THIS AFTERNOON. HOWEVER...ENVIRONMENTAL CONDITIONS ARE EXPECTED TO GRADUALLY BECOME MORE FAVORABLE FOR SOME DEVELOPMENT AS THIS SYSTEM MOVES WESTWARD AT 15 TO 20 MPH.

Look at one of 90L's (Dean's):
563
ABNT20 KNHC 111520
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1130 AM EDT SAT AUG 11 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD SURFACE TROUGH OVER THE WESTERN CARIBBEAN SEA IS PRODUCING
SHOWERS AND THUNDERSTORMS NEAR JAMAICA...THE CAYMAN ISLANDS...AND
SOUTHERN CUBA. ANY DEVELOPMENT OF THIS SYSTEM DURING THE NEXT
COUPLE OF DAYS SHOULD BE SLOW TO OCCUR AT IT MOVES WESTWARD AT
ABOUT 10 MPH.

A VIGOROUS TROPICAL WAVE HAS EMERGED FROM AFRICA OVER THE FAR
EASTERN ATLANTIC OCEAN. GRADUAL DEVELOPMENT OF THIS SYSTEM IS
POSSIBLE
DURING THE NEXT COUPLE OF DAYS AS IT MOVES WESTWARD AT 15
TO 20 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER KNABB
Member Since: September 7, 2006 Posts: 91 Comments: 2679
582. nash28
9:24 PM GMT on August 28, 2007
Oh look who came by...

The ho hum group.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
581. Drakoen
9:24 PM GMT on August 28, 2007
Amystery thanks for stretching the blog...
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580. extreme236
9:24 PM GMT on August 28, 2007
Amy is just upset that she may be wrong...
Member Since: August 2, 2007 Posts: 19 Comments: 19234
579. extreme236
9:24 PM GMT on August 28, 2007
Downcaster Amy has returned!! And know it is not disorganized Amy. Did the NHC say that?
Member Since: August 2, 2007 Posts: 19 Comments: 19234
577. extreme236
9:23 PM GMT on August 28, 2007
Oh, I know just because Dean did doesnt mean 94L will, I am just reminding people that Dean had several similiar messages on the TWO as 94L has had
Member Since: August 2, 2007 Posts: 19 Comments: 19234
574. rwdobson
9:21 PM GMT on August 28, 2007
again, if you're making comparisons to dean, you should be real careful. completely different storm. sure, 94L may develop, pretty good chance, but don't say because dean did, 94L will.
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573. extreme236
9:20 PM GMT on August 28, 2007
The nhc said several times that dean didnt become better organized, and then it gradually did. they are probably wanting to see a QS pass to see how the circulation looks
Member Since: August 2, 2007 Posts: 19 Comments: 19234
572. WeatherfanPR
9:16 PM GMT on August 28, 2007
TWO BY NHC:

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE LOCATED
ABOUT MIDWAY BETWEEN AFRICA AND THE LESSER ANTILLES HAVE NOT BECOME
ANY BETTER ORGANIZED THIS AFTERNOON. HOWEVER...ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO GRADUALLY BECOME MORE FAVORABLE FOR SOME
DEVELOPMENT AS THIS SYSTEM MOVES WESTWARD AT 15 TO 20 MPH.

THIS SHOULD SAY :

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE LOCATED ABOUT MIDWAY BETWEEN AFRICA AND THE LESSER ANTILLES HAVE BECOME BETTER ORGANIZED THIS AFTERNOON. CONDITIONS ARE FAVORABLE FOR A TROPICAL DEPRESSION TO FORM IN THE NEXT 24 TO 48 HRS AS THIS SYSTEM MOVES WESTWARD AT 15 TO 20 MPH.
Member Since: Posts: Comments:
571. nash28
9:18 PM GMT on August 28, 2007
Michael- How do you "look" to the 2008 season?

It's not like a sports team that got knocked out of the playoffs...

And this season hasn't even reached the PEAK YET!
Member Since: July 11, 2005 Posts: 190 Comments: 16972
570. Weather456
9:12 PM GMT on August 28, 2007
Well u cant beat the NHC...if they said so...they dont make up things...maybe they used data we the public dont have access to. The NHC sayin what they said at 5:30 pm doesnt mean a thing. Most of our tropical systems in past years started out with TWOs like that. So have some patience.
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568. Bobbyweather
5:16 PM EDT on August 28, 2007
28/1145 UTC 10.3N 39.7W TOO WEAK 94L (as of 7:45 AM.)
Member Since: September 7, 2006 Posts: 91 Comments: 2679
566. nash28
9:16 PM GMT on August 28, 2007
As I said... There are so many people that as soon as an Invest has been declared, they expect a TD come the 5pm advisory.

This one will take more time than Dean did.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
565. extreme236
9:16 PM GMT on August 28, 2007
has the sun set over 94L yet?
Member Since: August 2, 2007 Posts: 19 Comments: 19234
564. Bobbyweather
5:16 PM EDT on August 28, 2007
000
ABNT20 KNHC 282102
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 PM EDT TUE AUG 28 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

DISORGANIZED SHOWERS AND THUNDERSTORMS EXTENDING FROM HONDURAS
NORTHEASTWARD TO THE CAYMAN ISLANDS ARE ASSOCIATED WITH A TROPICAL
WAVE. DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED DUE TO PROXIMITY
TO LAND. HOWEVER...LOCALLY HEAVY RAINFALL IS POSSIBLE OVER
PORTIONS OF CENTRAL AMERICA AND THE YUCATAN PENINSULA DURING THE
NEXT DAY OR SO AS THIS SYSTEM CONTINUES WESTWARD.

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE LOCATED
ABOUT MIDWAY BETWEEN AFRICA AND THE LESSER ANTILLES HAVE NOT BECOME
ANY BETTER ORGANIZED THIS AFTERNOON. HOWEVER...ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO GRADUALLY BECOME MORE FAVORABLE FOR SOME
DEVELOPMENT AS THIS SYSTEM MOVES WESTWARD AT 15 TO 20 MPH.

DISORGANIZED SHOWERS AND THUNDERSTORMS LOCATED A COUPLE HUNDRED
MILES SOUTHEAST OF WILMINGTON NORTH CAROLINA IS ASSOCIATED A
NON-TROPICAL AREA OF LOW PRESSURE. WHILE ENVIRONMENTAL CONDITIONS
ARE NOT CURRENTLY FAVORABLE FOR DEVELOPMENT...THEY COULD BECOME
MORE FAVORABLE OVER THE NEXT COUPLE OF DAYS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$

FORECASTER RHOME

Well, there is a new feature- and also, welcome TD 10W to the tropics.
Member Since: September 7, 2006 Posts: 91 Comments: 2679
563. Drakoen
9:15 PM GMT on August 28, 2007
Posted By: nash28 at 9:15 PM GMT on August 28, 2007.

And that's a bad thing Michael?


LoL. i would make the same assumption as well. Don't want to get into it though...
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561. extreme236
9:15 PM GMT on August 28, 2007
well 94L could still shield itself from the dry air like dean, a lot of storms shield themselves from dry air
Member Since: August 2, 2007 Posts: 19 Comments: 19234
558. nash28
9:14 PM GMT on August 28, 2007
And that's a bad thing Michael?
Member Since: July 11, 2005 Posts: 190 Comments: 16972
557. rwdobson
9:13 PM GMT on August 28, 2007
"it is being compared to dean based upon the potential track. dean formed farther east due to more favorable conditions and a more organized wave as it came off africa"

some people are also saying things like "dean handled the dry air, so 94L should be able to". however, as you noted, there are some differences...dean was much better set-up to form into a major storm.
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555. nash28
9:12 PM GMT on August 28, 2007
This will take a couple of days to organize. There will not be a TD tonight, nor most likely tomorrow.

Look for Thursday.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
554. extreme236
9:12 PM GMT on August 28, 2007
well TD 10W is forecasted to become yet another typhoon. it seems almost all of the systems there have become typhoons
Member Since: August 2, 2007 Posts: 19 Comments: 19234
553. JLPR
9:12 PM GMT on Agosto 28, 2007
well i would say fair satellite presentation
decent low at 1009mb
needs more convection
what else?
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551. nash28
9:10 PM GMT on August 28, 2007
Wishful thinking Sunny???

Boy, you are a real piece of work.

Anything to downplay.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
550. Drakoen
9:11 PM GMT on August 28, 2007
I see an area of concentrated thunderstorm right over the low pressure center.
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549. extreme236
9:10 PM GMT on August 28, 2007
Oh my, it seems the downcasters are in full force, if Amystery was here this would be aweful lol
Member Since: August 2, 2007 Posts: 19 Comments: 19234
548. Drakoen
9:10 PM GMT on August 28, 2007
Posted By: LLJ at 9:10 PM GMT on August 28, 2007.

nice satellite presentation.


Of what?


94L.
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547. Hawkeyewx
4:08 PM CDT on August 28, 2007
The NHC is right. 94L doesn't look much different than yesterday. At the surface it still looks broad and weak, and there is still no concentrated deep convection.
Member Since: July 5, 2005 Posts: 2 Comments: 1924
545. extreme236
9:09 PM GMT on August 28, 2007
Posted By: gsueagle07 at 9:07 PM GMT on August 28, 2007.

Oh no....the NHC says the showers havent' become any better organized with 94L with the 530PM update....so what are y'all seeing??....just curious


Im thinking they are basing it upon the overall circulation. it isnt as well defined yet. When QS comes in that will help them figure out the strength and elongation of the circulation now
Member Since: August 2, 2007 Posts: 19 Comments: 19234
544. Tazmanian
9:08 PM GMT on August 28, 2007
ABNT20 KNHC 282102
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 PM EDT TUE AUG 28 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

DISORGANIZED SHOWERS AND THUNDERSTORMS EXTENDING FROM HONDURAS
NORTHEASTWARD TO THE CAYMAN ISLANDS ARE ASSOCIATED WITH A TROPICAL
WAVE. DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED DUE TO PROXIMITY
TO LAND. HOWEVER...LOCALLY HEAVY RAINFALL IS POSSIBLE OVER
PORTIONS OF CENTRAL AMERICA AND THE YUCATAN PENINSULA DURING THE
NEXT DAY OR SO AS THIS SYSTEM CONTINUES WESTWARD.

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE LOCATED
ABOUT MIDWAY BETWEEN AFRICA AND THE LESSER ANTILLES HAVE NOT BECOME
ANY BETTER ORGANIZED THIS AFTERNOON. HOWEVER...ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO GRADUALLY BECOME MORE FAVORABLE FOR SOME
DEVELOPMENT AS THIS SYSTEM MOVES WESTWARD AT 15 TO 20 MPH.

DISORGANIZED SHOWERS AND THUNDERSTORMS LOCATED A COUPLE HUNDRED
MILES SOUTHEAST OF WILMINGTON NORTH CAROLINA IS ASSOCIATED A
NON-TROPICAL AREA OF LOW PRESSURE. WHILE ENVIRONMENTAL CONDITIONS
ARE NOT CURRENTLY FAVORABLE FOR DEVELOPMENT...THEY COULD BECOME
MORE FAVORABLE OVER THE NEXT COUPLE OF DAYS.

Member Since: May 21, 2006 Posts: 5091 Comments: 115456

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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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