Disturbance 94L in Central Atlantic; NHC management changes

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

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


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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494. Weather456
8:41 PM GMT on August 28, 2007
TRMM Rain Rate Pass

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493. extreme236
8:41 PM GMT on August 28, 2007
So, who wants to take a vote that Amystery's prediction will be wrong? lol
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492. CFL
8:35 PM GMT on August 28, 2007
i think that all 94l needs is a good, long burst of convection to get itself together and become a TD.
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491. Bonedog
4:40 PM EDT on August 28, 2007
10.5 is on the border usually anything below 10 is bad. But I think at the 5pm they will reposition it closer to 12
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490. putintang3
8:35 PM GMT on August 28, 2007
Posted By: StormHype at 8:34 PM GMT on August 2Change "Most" to "Some" and I would agree. Most are wishcasters hoping for chase opportunity, a day off school, or just want to sensationalize the reality of what's going on. Quiet now, but they come out of the woodwork like termites once a named storms forms in the ATL.
8, 2007


Well if most had something better to do than to sit staring at a couple of models all day maybe they wouldn't make more of things. Like me, I have nothing else to do, just trying to stay cool.
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489. Weather456
8:37 PM GMT on August 28, 2007
Lastest WV 37H Brightness from the TRMM, this is a bit outdated but it is the lastest and most likely alot has change since then

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488. extreme236
8:39 PM GMT on August 28, 2007
Posted By: gsueagle07 at 8:39 PM GMT on August 28, 2007.

Isn't 10.5 really really far south??....


No, Ivan formed at like 9.5
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487. JLPR
8:38 PM GMT on Agosto 28, 2007
well lets see maybe it will be a slow one getting the
...however if it changes in organization just a bit it could be a depresion...
for some time
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486. gsueagle07
8:38 PM GMT on August 28, 2007
Isn't 10.5 really really far south??....
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485. Tazmanian
8:34 PM GMT on August 28, 2007
EF2 Fenton, Michigan tornado by JeffMasters



Caption:
The August 24, 2007 Fenton Michigan tornado was rated EF2 when it plowed through downtown Fenton. I saw tons of splintered trees, but damage to structures was minimal. From the NWS storm report:

thanks dr m for the photos

more of dr m photos here

Link
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484. Bonedog
4:29 PM EDT on August 28, 2007
as for folks thinking we are disagreeing with the Doc. we are not disagreeing with what he posted earlier today what we are discussing is its current state. Just as is probably happening behind the sceens at the NHC.

Weather changes as the day progresses what was at 9am is now diffrent at 4pm.

Thats all.
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483. StormHype
8:27 PM GMT on August 28, 2007
Most people making forecasts on this site are very knowledgeable and very few make clueless fear mongering forecasts for sure. So while this is definetly not the place to come for official forecasts, you will normally get fact-based opinion on what could happen.


Change "Most" to "Some" and I would agree. Most are wishcasters hoping for chase opportunity, a day off school, or just want to sensationalize the reality of what's going on. Quiet now, but they come out of the woodwork like termites once a named storms forms in the ATL.
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482. Weather456
4:56 PM GMT on August 28, 2007
Afternoon All

I must say 94L looks a little better organize

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480. rwdobson
8:30 PM GMT on August 28, 2007
Dean was similar but not the same. for one thing, the models jumped on dean developing pretty quickly, i recall.
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479. Tazmanian
8:26 PM GMT on August 28, 2007
cant we this call 94L a cat 5 and get it overe with come on now we dont no what 94L is up too it is this too soon to tell what wait for a TD then we can see what kind of track the nhc has for 94L it could go N it could go W it could go for S FL and the gulf or it could go the Caribbean and then the NE Caribbean and then the gulf or out to sea we this dont no where its going at this time
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477. extreme236
8:28 PM GMT on August 28, 2007
well actually 94W is gone in the wpac, it is now 10W
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475. Bonedog
4:26 PM EDT on August 28, 2007
rwdobson. It was the same way with Dean and we all know what happened with that one. If you look just above the storms perifery you will notice the brown change twords black and grey. That shows moisture developing. As a storm gets its act together it pulls moisture from the sea and adds it to the atmosphere creating a cocoon. Its a hinderance to storms that are not as well organized as 94L.
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473. putintang3
8:18 PM GMT on August 28, 2007
yea Real I think you may me right on the Carribean wave it does seem to be moving a little northward. hum???/
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472. 786
7:56 PM GMT on August 28, 2007
For Dean I think the GFS was the most accurate so I'm really interested to see how it develops 94L.

Can anyone explain or guide me to a site that can help me understand what troughs and ridges do and how LLC and ULD play a role.

Would be much appreciated, I think after I get a grip on that I'll be able to see the full picture.
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471. JLPR
8:25 PM GMT on Agosto 28, 2007
did someone notice we are at the number 94 invest in all basins
weird :P
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470. HurricaneMyles
8:21 PM GMT on August 28, 2007
Most people making forecasts on this site are very knowledgeable and very few make clueless fear mongering forecasts for sure. So while this is definetly not the place to come for official forecasts, you will normally get fact-based opinion on what could happen.
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469. Bonedog
4:23 PM EDT on August 28, 2007
hos the models change from run to run. Things change. When Doc posted up this morning it wasnt as impressive as it is now. Also the models did start showing something at the 12Z run which was a few hours after the docs post.
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468. StormHype
8:22 PM GMT on August 28, 2007
StormW said...
Excuse me!


Not all are in that lot, including yourself StormW, but there are many others who are. Proof is in the blog trails.
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467. extreme236
8:24 PM GMT on August 28, 2007
Posted By: hosweather at 8:23 PM GMT on August 28, 2007.

Notice that none of Dr. Jeff's "reliable" models are developing 94l into anything significant. You guys don't seem to believe his reliable models are reliable.


None of the reliable models developed Erin as well. the CMC did. Dont trust the models as gospel
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466. rwdobson
8:21 PM GMT on August 28, 2007
Bonedog, the dry air is significant to the north. it may or may not be able to "negate" it.
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465. Bonedog
4:22 PM EDT on August 28, 2007
srada the front will stop its southward push and begin moving it west. No storm can overtake a front so as the front comes in from the west it will force the storm out to sea. No worries buddy.
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464. hosweather
8:14 PM GMT on August 28, 2007
Notice that none of Dr. Jeff's "reliable" models are developing 94l into anything significant. You guys don't seem to believe his reliable models are reliable.
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463. extreme236
8:21 PM GMT on August 28, 2007
and those who say there is too much dry air for development, if you remember dean, it moved the dry air north, it pulled moisture in from the south. it produced a self sustaining enviroment for itself
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462. Bonedog
4:17 PM EDT on August 28, 2007
stop saying dry air. It has dry air to the north but in front of it is moist air. As it gets its act together it will add moisture to its environment and thus negate the dry air to its north. Also the dry air in the Carib could be gone by the time it arrives in 3 or 4 days.

94L
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460. srada
8:18 PM GMT on August 28, 2007
FXUS62 KILM 281917
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
317 PM EDT TUE AUG 28 2007

.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 --

This is what our local mets are saying about the low off the carolina coast, wouldnt that cold front hindered it moving out to sea?
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459. extreme236
8:18 PM GMT on August 28, 2007
dont know what WV loops your looking at GSU, but the dry air in the caribbean isnt bad, and mainly confined to the eastern area. also, 94L is also better organized and it would be hard to not see that as well...
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458. StormHype
8:10 PM GMT on August 28, 2007
LLJ said...
"I am on this site because I have learned to not trust TV Mets. If you guys trust them, that's great. But why are you here if they are all you need?"


If you think you can trust the posts here for better outlook than from TV mets, you've definitely come to the wrong place.

There is no control on who can post here, thus you end up with clueless fear mongers making forecasts based on emotions and 'gut feelings'.

Go to nhc.gov for a real tropical forecast if you don't trust your TV met. However, TV mets pretty much just regurgitate NHC calls, but not as quickly as you can get them off the net.
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457. Crawls
8:17 PM GMT on August 28, 2007
Can someone please tell me how to post an image?
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456. chevycanes
8:16 PM GMT on August 28, 2007
NHC says the wave in the Caribbean is heading west. its not gonna form into anything before hitting land.
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455. gsueagle07
8:13 PM GMT on August 28, 2007
I have to agree with the Dr....just too much dry air...even in the Carribean...
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453. Bonedog
4:13 PM EDT on August 28, 2007
LOL "blob" It is way more than that LOL
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452. amazinwxman
8:13 PM GMT on August 28, 2007
Things are starting to get perky again. Obviously 94L is at the forefront of most discussions, as well it should - it has the benefits of a respectable low level cyclonic turning, favorable latitude, some convection already present... and time. 93L probably ran out of time (land) before it could get a position.

Also worth noting, the surface wave and associated mid-level low which is crossing through and just north of Nicaragua today. It appears that the mid-level circulation is not running amok inland, and that if anything, there has been some slight pull more to the northwest, than due west over the last 18 hours or so, which appears to have allowed some subtle curved banding to develop today, most evident near 17N 85W, and to either rise of that down to about 15, and with some inflow from the SE all the way down to 10N. Despite being so close to and/or partially overland, just a little more development here could warrant an invest tag, as well.

One final note, there appears to be a good bit of SAL mixing in from east of about 55W and extending all the way from the ITCZ to roughly 20N (even beyond this, but that seems to be containing the especially healthy amounts of it). Could act to hold back 94L a bit longer. If it stays too weak and too far south it will clearly run itself into South America with no further development in this basin.
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451. rwdobson
8:13 PM GMT on August 28, 2007
"So can we call 94l a "blob" now?"

actually, i think a number invest is already a step above a blob...
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450. mostormspotter
3:11 PM CDT on August 28, 2007
So can we call 94l a "blob" now?
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449. Bonedog
4:10 PM EDT on August 28, 2007
sorry was working. JustCurious no problem glad I could help.
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448. Tazmanian
8:09 PM GMT on August 28, 2007
extreme236 i no but if this dos or not go in to S FL then the gulf wish i hop not then we could be looking at a cat 5 in the gulf why not the sea temps are red hot


not puting a doom on any one this saying it could
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447. WeatherfanPR
8:10 PM GMT on August 28, 2007
what's correct: diurnal max or dinural max?
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446. keisa90
8:08 PM GMT on August 28, 2007
I'm glad someone else is seeing that GetReal. I was asking about the same thing but didn't get a response.
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445. extreme236
8:08 PM GMT on August 28, 2007
wow that disturbance in the caribbean looking impressive. may try to develop quickly before second landfall
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444. Crisis57
8:07 PM GMT on August 28, 2007
what are the models showing as a current movement a west track or wnw
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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