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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393. srada
7:41 PM GMT on August 28, 2007
thanks bonedog,

but if something forms between now and the cold front moving in, what will happen with the system, is this a if and when developing situation?

New at this, so bare with my questions, love the weather though!
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392. ClearH2OFla
3:38 PM EDT on August 28, 2007
Grr I live like 5 min from clw campus. Already have a BS and BA from SOuth Florida in History and Social Education. But always been fascinated with weather. So to 94l any chance this becomes Dean little brother.
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391. amazinwxman
7:42 PM GMT on August 28, 2007
From the NWS site wx discussion for coastal NC:

SYNOPSIS...
-- Changed Discussion --A WEAK COLD FRONT JUST TO OUR SOUTH AND EAST WILL CONTINUE TO SLOWLY
DISSIPATE OVERNIGHT. A WEAK AREA OF HIGH PRESSURE WILL BUILD SOUTH
AND ACROSS THE AREA ON WEDNESDAY AND THURSDAY AS AN AREA OF LOW
PRESSURE TRIES TO TAKE SHAPE OFF OF THE CAROLINA COAST AND LINGERS
OFFSHORE INTO THE WEEKEND. A STRONG COLD FRONT WILL SLOW ITS
SOUTHWARD PUSH...BUT SHOULD MOVE INTO THE AREA BY THE WEEKEND.-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --THE CENTER OF THE UPPER RIDGE ACROSS FLORIDA WILL KEEP A DRY
NORTHWEST FLOW GOING TONIGHT AT 500 MB. AT THE SURFACE A WEAK COLD
FRONT NEAR SAVANNAH WILL CONTINUE TO WEAKEN OVERNIGHT. SURFACE LOW
PRESSURE ABOUT 100 MILES EAST OF CAPE FEAR IS FORECAST TO DRIFT
SLOWLY SOUTH OR SOUTHEAST TONIGHT WITH LITTLE CHANGE IN STRENGTH.
ALTHOUGH NOT EXPECTED...SIGNIFICANT AND RAPID CHANGES COULD OCCUR
WITH THIS SYSTEM IF CONVECTION WERE TO INCREASE SUBSTANTIALLY FROM
ITS CURRENT STATE.

DAYTIME CUMULUS WILL GRADUALLY ERODE THIS EVENING WITH GENERALLY
CLEAR SKIES EXPECTED. THE NORTHWEST MID LEVEL FLOW WILL ADVECT SOME
CONVECTIVE DEBRIS CLOUDINESS IN FROM SHOWERS AND STORMS FIRING THIS
AFTERNOON ACROSS THE HIGH TERRAIN OF WESTERN NORTH CAROLINA. THE NAM
PICKS UP ON THIS AND SHOWS THE TRANSIENT CLOUDINESS WILL MAINLY
IMPACT THE PEE DEE REGION. THERE IS THE POTENTIAL FOR PATCHY FOG
MAINLY INLAND LATE TONIGHT WITH LIGHT LOW LEVEL WINDS EXPECTED. WITH
FAIRLY GOOD RADIATIONAL COOLING OVERNIGHT TEMPERATURES SHOULD FALL
TO 68-72...COOLEST ACROSS INLAND SOUTHEAST NORTH CAROLINA.-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
-- Changed Discussion --DRY WITH NEAR CLIMO TEMPERATURES EXPECTED ON WEDNESDAY AS DRY AIR
ALOFT MOVES INTO THE REGION. FORECAST SOUNDINGS SHOW SOME CAPPING
AROUND 700MB WHICH WILL LEAD TO SOME FLAT CU BUT LITTLE IN THE WAY
OF PRECIP. THINK RH WILL BE LOW ON WEDNESDAY TOO AS DRIER AIR ALOFT
IS MIXED DONE TO THE SURFACE.

SHORT WAVE DROPS IN FROM THE NORTHWEST THURSDAY...HELPING TO BRING
IN SOME MID LEVEL MOISTURE. GFS/NAM/CANADIAN ALL SHOW THE WAVE BUT
DIFFER ON LOCATION. GFS/CANADIAN HAVE IT FARTHER SOUTH...KEEPING
DRIER AIR OVER MOST OF THE CAROLINAS AND RESULTING IN LITTLE TO NO
PRECIP. THE NAM MOVES THIS WAVE ALONG THE NC/SC BORDER...RESULTING
IN SOME PRECIP ACROSS SC. BECAUSE CONFIDENCE IS LOW IN THE NAME
SOLUTION HAVE DECIDED TO TRIM BACK POPS A LITTLE FOR THURSDAY.
TEMPERATURES WILL BE AT TO SLIGHTLY BELOW CLIMO WITH NORTH TO
NORTHEAST FLOW AND FALLING HEIGHTS.

BIG CAVEAT TO FORECAST REMAINS WHAT HAPPENS TO SURFACE TROF/LOW OFF
THE EAST COAST. CURRENTLY THERE IS SOME CONVECTION ALONG THE TROF
AXIS...BUT THERE IS A LOT OF DRY AIR JUST NORTH OF THIS FEATURE.
GUIDANCE HANDLES THIS FEATURE IN DIFFERENT WAYS. SOME MODELS WANT TO
SPIN IT UP INTO A TROPICAL OR SUB-TROPICAL SYSTEM WHILE OTHERS KEEP
A WEAK SURFACE LOW ON THE TROF. FAVORED THE GFS SOLUTION WHICH HAS A
WEAK LOW BUT NO DEVELOPMENT.-- End Changed Discussion --

&&

390. groundswell
7:40 PM GMT on August 28, 2007
srada-out to sea, but maybe waves down the se coast.
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388. extreme236
7:41 PM GMT on August 28, 2007
ok, it seems that the spaghetti models agree for the most part on where it will go in the next 24hrs or so, just not after that lol
Member Since: August 2, 2007 Posts: 19 Comments: 19234
387. Bonedog
3:40 PM EDT on August 28, 2007
srada a cold front is expected to move off the coast later this week which will kick anything out to sea from the Carolina system
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386. hurricane23
3:36 PM EDT on August 28, 2007
94L according to the lasest EURO will take a very similar path to dean.It has a 500mb ridge to its north at 168hrs and it also appears that it trys to strengthen the ridge a bit which would suggest a westward path into the caribbean.Its still early but from what iam getting this system will have a hard time moving north of the islands.Adrian
Member Since: May 14, 2006 Posts: 8 Comments: 13843
383. srada
7:38 PM GMT on August 28, 2007
are the steering currents weak in this area or is there a high that will pull this out to sea?
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382. extreme236
7:38 PM GMT on August 28, 2007
yes I noticed that Storm, the enviroment very favorable in terms of shear. wind shear also favorable for the disturbance off the carolinas
Member Since: August 2, 2007 Posts: 19 Comments: 19234
381. Bonedog
3:36 PM EDT on August 28, 2007
extreme latest winds are 4 to 17knts but the wind field covers from 10 to 200 degress so there is definatley something there just needs to organize around a LLC
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379. mississippiwx23
7:36 PM GMT on August 28, 2007
srada,

Likely yes.
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377. extreme236
7:36 PM GMT on August 28, 2007
Posted By: srada at 7:36 PM GMT on August 28, 2007.

I had asked this earlier today but got no response,so Ill ask again, If something develops off the carolina coast, will this head out to sea?

Thanks


Most likely. I have noticed it is moving NE, so it will probably move out to sea, but I am not sure of that for a fact
Member Since: August 2, 2007 Posts: 19 Comments: 19234
376. blueranch
7:35 PM GMT on August 28, 2007
is it being said that the carolina 'thing' could turn into a storm?
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375. srada
7:35 PM GMT on August 28, 2007
I had asked this earlier today but got no response,so Ill ask again, If something develops off the carolina coast, will this head out to sea?

Thanks
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374. extreme236
7:35 PM GMT on August 28, 2007
how high are the winds with the carolina system?
Member Since: August 2, 2007 Posts: 19 Comments: 19234
373. Bonedog
3:32 PM EDT on August 28, 2007
extreme I spoted the Carolina system earlier with JP. Already has a wind field associated with it as seen from QS pass, ship and bouy obs.

All the models on the CPE develope it to a warm core system.
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372. Tazmanian
7:32 PM GMT on August 28, 2007
whats wait and see when they call this a TD then we will no what kind of track the nhc has for it
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370. boobless
7:23 PM GMT on August 28, 2007
Posted By: boobless at 6:57 PM GMT on August 28, 2007.
Just for kicks, I'd watch the patch of cumulus NW of 94L on a wide view vis centered near 17N 55W.


What I meant was: Does this patch of clouds turn right in the near future? Not that I detected a spin...
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369. extreme236
7:27 PM GMT on August 28, 2007
a few models seem to develop something off the carolina coast in the next 24-48hrs. Most models keep it weak though
Member Since: August 2, 2007 Posts: 19 Comments: 19234
368. Bonedog
3:29 PM EDT on August 28, 2007
should only be a few more hours before the sun sets over 94L
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367. ClearH2OFla
3:29 PM EDT on August 28, 2007
Hey Storm W Do they teach met At St. Pete College.
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366. ClearH2OFla
3:28 PM EDT on August 28, 2007
Hey all lunch time Nash whats up with 94l short term and long term. If you will be so kind
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365. Tazmanian
7:28 PM GMT on August 28, 2007
extreme236 but it has been holdeing up vary well today this wait in tell night
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363. Bonedog
3:27 PM EDT on August 28, 2007
just currious you might have missed my answer to your question check at the top of this page and just above the graphic on the previous page.
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362. Tazmanian
7:26 PM GMT on August 28, 2007
ok 28 you are right thiss wenting evere one no that it takes 94L up to 91kt in 120hrs or so but your right what see if this comes a TD or TS 1st
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361. cchsweatherman
7:26 PM GMT on August 28, 2007
That is the best description I have ever heard of about an invest runnomore. I like that alot being a football fan and all.
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359. extreme236
7:26 PM GMT on August 28, 2007
the circulation is fairly well defined, but the convection just hasnt organized much around it yet
Member Since: August 2, 2007 Posts: 19 Comments: 19234
358. IKE
2:25 PM CDT on August 28, 2007
HWRF develops a system in the NE GOM similar to what the GFS is hinting at....

HWRF model run...Link
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357. sporteguy03
7:24 PM GMT on August 28, 2007
Posted By: mgreen91 at 7:20 PM GMT on August 28, 2007.
Where is stromkat? I would like to know what he thinks about 94L.

He'll probably say its going to hit NOLA like always.
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355. runnomore
7:24 PM GMT on August 28, 2007
Watching an invest is like watching pre-season football to many players to be able to decide the outcome. But still fun to watch.
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354. nash28
7:24 PM GMT on August 28, 2007
Taz- I wouldn't put much stock in the SHIPS intensity forecast just yet. Let's get a system that has at least developed into a TD or TS, then we'll start looking at intensity guidance.
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353. Bonedog
3:23 PM EDT on August 28, 2007
also if you look at the QuckSCAT main page you will see little elipses all across the page. If you actually took that page and cut it out and wraped it around a ball you will see what I mean about the curvature of the Earth. Basically its the horizons shadow relative to the field of view.
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352. extreme236
7:22 PM GMT on August 28, 2007
I dont use ship intensity, it is almost never right
Member Since: August 2, 2007 Posts: 19 Comments: 19234
350. extreme236
7:23 PM GMT on August 28, 2007
watch the disturbance off the carolina coast though, likely invest in the future. looks fairly well organized
Member Since: August 2, 2007 Posts: 19 Comments: 19234
349. Tazmanian
7:22 PM GMT on August 28, 2007
this says 94L will be a strong cat 2 storm it take 94L up to 91kt winds in 120hrs or so

lol
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348. mississippiwx23
7:19 PM GMT on August 28, 2007
The european drops the circulation after half of the run (130hrs or so). However, it is there for the first 4 frames, just weak.
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347. extreme236
7:21 PM GMT on August 28, 2007
HWRF seems to show a good run. Develops it as a weak system, which I believe would make since.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
346. Bonedog
3:21 PM EDT on August 28, 2007
just curious it misses certaina reas on certain passes due to the curvature of the Earth and its limited field of view. It follows slightly diffrent paths each pass as it circumnavigates the globe.
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345. extreme236
7:21 PM GMT on August 28, 2007
18:45 UTC image shows convection increasing a bit. still somewhat sloppy
Member Since: August 2, 2007 Posts: 19 Comments: 19234
344. sunnyandshear
7:21 PM GMT on August 28, 2007
Firstly, Orlando, isn't in South Florida. According to your own statement then, Wilma hit South Florida before the cold front did.

You go on to state:
""first off basic meteorological knowledge states that a storm system cant cross a front, so your statement would never be relevant anyway""

I say that talking about basic knowledge is easy, demonstrating it, much more difficult.
If I decipher your snippy remarks correctly, you seem to be comfirming my earlier comment concerning cold fronts and hurricanes.
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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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