ATL : HARVEY - Tropical Depression - Discussion

[maxx9512]

Ex-93L looks better this morning than it has in the last few days. Kinda looks like Emily did with two blobs as it
neared the islands. Has it a chance to regain invest status or will it just remain as a tw?

Just noticed on the NRL site that they have 93L listed again. I believe it was not listed as of yesterday. Also I
don't see it on the SFWMD models page. A comeback?

Now back on SFWMD! Spoke a minutes too soon! As soon as posted it changed.

[Gustywind]

000
AXNT20 KNHC 151201
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON AUG 15 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1015 UTC.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 53W FROM 10N T0 17N.
NUMEROUS STRONG RAINSHOWERS AND THUNDERSTORMS ARE FROM 14N TO
17N BETWEEN 53W AND 57W...AND FROM 13N TO 15N BETWEEN 58W AND
60W. SOME OF THE PRECIPITATION MUST BE REACHING BARBADOS.
THE ISLANDS FROM SAINT VINCENT TO DOMINICA MAY BE THE NEXT ONES
FOR THE STRONG RAINSHOWERS AND THUNDERSTORMS DURING THE NEXT
FEW HOURS IF THE CURRENT PRECIPITATION PATTERN MAINTAINS ITSELF
AND CONTINUES MOVING WESTWARD.

$$
MT

[GCANE]

Cloud tops improving.

[KWT]

With such a weak area of Vort with it I'm abit wary this will be a burst then poof type system at the moment so I'm not too excited by this recent burst.

[Gustywind]

From our friend Rob Lightbown of CrownWeather August 15, 2011, 6:00 am
http://www.crownweather.com/?page_id=4557

Invest 93L Located To The East Of The Lesser Antilles:
Satellite imagery this morning showed some deep convection developing around what was Invest 93L now located between 50 and 55 West Longitude. Analysis of ocean water temperatures reveals that this disturbance has just entered ocean water temperatures warmer than 84 degrees Fahrenheit. The combination of a more favorable upper level environment and these warmer ocean water temperatures are likely the reasons for the marked increase in convection this morning. A view of the water vapor satellite loops shows that there is a lot of dry air surrounding this disturbance and any development that does occur will be slow to happen.

Neither the GFS or European model guidance forecasts development of 93L and they both keep it a tropical wave which eventually tracks into Central America on Friday. Now, the NAM model has been fairly insistent on forecasting the development of this system. The current forecast run of the NAM model forecasts that 93L will track across Barbados today and then across the southern Leeward Islands and the Windward Islands tonight into Tuesday, which I do agree with. The NAM model then forecasts that this disturbance will develop into a tropical cyclone as we get into Wednesday and for it to strengthen into a moderate tropical storm on Thursday with it beginning to impact Jamaica during Thursday afternoon.

The NOGAPS model forecasts that 93L will develop into a tropical cyclone once it reaches the west-central Caribbean just south of Jamaica on Thursday and then forecasts it to impact Central America and Belize as a fairly weak tropical storm this coming weekend.

Here are my thoughts on 93L: Even though we are seeing a marked increase in convection this morning that development of Invest 93L will be slow to occur and the NAM model’s forecast should not be trusted. Why?? The eastern Caribbean is essentially a desert in the mid and upper levels of the atmosphere and once this disturbance starts trying to develop and intensify it will likely suck in this dry air and weaken. So, I really do not think 93L will become a tropical depression over at least the next couple of days, however, it will bring strong gusty winds, choppy seas and heavy rainfall across Barbados, the Windward Islands and the southern Leeward Islands from today through Tuesday.

I do think that 93L will find a more favorable environment for development once it reaches the central and western Caribbean later this week and this is when we may see it organize into a tropical depression or a tropical storm. Given this, it would probably track west-northwestward right into Central America and Belize this coming weekend as a tropical depression or perhaps a tropical storm.

As it stands right now, 93L is not a immediate concern and there is the possibility that it may never develop. With that said, this disturbance will be watched closely this week and I will keep you all updated on the latest.

Off topic:
New Tropical Wave Now Coming Off Of Africa:
Satellite imagery from western Africa showed a fairly robust tropical wave now tracking into the far eastern Atlantic from the west coast of Africa. The GFS and European model guidance are very insistent on that this will develop into a tropical cyclone as it approaches the Lesser Antilles late this weekend into early next week. I am very skeptical of this right now, just because these same models forecasted 93L to be a strong hurricane as it approached the Lesser Antilles.

Looking at the environment ahead of this new tropical wave, there is dry air noted in the water vapor imagery between 35 and 55 West Longitude, although a large plume of moist air is observed east of 30 West Longitude and it’ll be interesting to see if this new tropical wave becomes embedded in this plume of moist air.

For now, it is something that I am going to keep a close eye on and I will say development, if any, will be slow to occur over the next several days.

Finally:
I still think that tropical activity as a whole will really ramp up with more intense systems starting late this week and then continuing into the Labor Day weekend. The latest Madden Julian Oscillation forecast indicates upward motion across the entire Atlantic basin for the next three weeks and this leads me to believe that it will become much more active with larger and stronger storms.

[GCANE]

I wouldn't be surprised if this tracks south of Jamaica, spins up strong in the west Carib, and moves into the GOM.

[NDG]

93L is most likely C.A. bound or MX at the most, with the ecmwf showing a narrow low latitude ridge build westward south of the eastern US trough that would keep 93L on mostly westward track.

[Gustywind]

Little closeup

[wxman57]

Looking at the GFS 400-700mb mean flow, it has a massive ridge over Texas for the next week with northerly winds from the southern U.S. to the Caribbean. Such flow would not allow any turn northwestward into the Gulf. That's why the GFS drives it into Central America. 00Z Euro has the ridge in the identical place through this week, though just a tad weaker than the GFS. It's also suggestive of a continued westward movement into southern Mexico or Central America. Same thing with Canadian, though it's a little stronger with the ridge than the Euro but a little weaker than the GFS.

Just nothing to indicate a track into the area from NE Mexico through the FL Panhandle should it develop. The weakness in the ridge to the north lies over the western Bahamas and across Florida, so there might be an opportunity for it to take a sharp northerly turn near Cuba. It would have to be a storm by then to have a chance to be picked up and turned north, probably.

[KWT]

Yeah the models are still pretty keen on having a strong dome of high pressure over the Gulf, pretty small chance of it being ovberdone I suppose but most likely track is indeed towards Central America...

Which to be fair would be a classic La nina track...I suspect all that a stronger system will do is maybe go closer to WNW rather then near due west.

[KWT]

One thing is for sure, convection that moves over the islands should make for an interesting day and night.

[Gustywind]

Given NRL site 93L is reactived.
http://www.nrlmry.navy.mil/tc-bin/tc_ho ... m&PROD=vis
Latest:
20110815.1115.93LINVEST.20kts-1010mb-133N-546W.

Latest from NRL. Looks like 93L has improved slightly... as winds estimations are approaching 25 kts compared to the last hour 20kts.
20110815.1215.93LINVEST.25kts-1010mb-135N-564W

[GCANE]

Pretty much a wave at this time.

Expect it to keep moving west.

[Gustywind]

Thunder is rumbling nicely with some very light gusts in my location.

[KWT]

Yep GCANE its still very weak, sorta to be expected given its only just recently flared up some decent convection.

I'd be rather surprised if it gets going before 70W, but I do think it has a fair shout of development after that...

[GCANE]

Yep GCANE its still very weak, sorta to be expected given its only just recently flared up some decent convection.

I'd be rather surprised if it gets going before 70W, but I do think it has a fair shout of development after that...

Agreed KWT, mid / west Carib is where the action usually happens.

[Aric Dunn]

Yep GCANE its still very weak, sorta to be expected given its only just recently flared up some decent convection.

I'd be rather surprised if it gets going before 70W, but I do think it has a fair shout of development after that...

Agreed KWT, mid / west Carib is where the action usually happens.

The problem it has had the whole time besides the dry air ( which is no longer as much of a problem) is its forward motion. It is moving way to fast and there is very little chance of closing off a LLC at that speed. on top of that its entering the eastern carrib were the flow will only get worse due to the geographical layout. unless it has a extremely large and sustained convective burst that can overcome both the forward motion and the low level flow, development is not likely till the western and NW carrib.

[northtxboy]

I am going to have to disagree. I think it will be a TD in the next 24 or 36 hours or even less. And I still beleave that it will make a run for the GOM not CA. But this is just my thoughts please look to the NHC for more info.

[Kory]

I am going to have to disagree. I think it will be a TD in the next 24 or 36 hours or even less. And I still beleave that it will make a run for the GOM not CA. But this is just my thoughts please look to the NHC for more info.

Looks nice on radar, but no LLC. I don't think the northern Gulf Coast has to worry, but the Yucatan and areas in the Bay of Campeche may have to keep an eye on this if it does take a more WNW course. The death ridge is back in place across Texas and the trough isn't strong enough to pull it north.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[KWT]

I am going to have to disagree. I think it will be a TD in the next 24 or 36 hours or even less. And I still beleave that it will make a run for the GOM not CA. But this is just my thoughts please look to the NHC for more info.

Well whilst its not impossible for this to pick up more latitude then expected, thqat upper high that is over Texas is pretty potent and I see no real way it can get into the Gulf.