ATL : HARVEY - Tropical Depression - Discussion

[FireRat]

Thanks for the info Kory,

I guess we can't write this one off yet, especially since shear is nearly absent. 93L is going to have to do something big tonight and tomorrow if this was to become a threat to the Leewards in a few days. Most likely at this point, I'd say some of the islands will have squally weather and gusty showers around the 16th of August.

[Gustywind]

From Rob Lightbown of CrowWeather on August 14, 2011, 10:08 am
http://www.crownweather.com/?page_id=4557

Invest 93L Located To The East Of The Lesser Antilles:
Invest 93L is located to the east of the Lesser Antilles this morning. The convection really died off yesterday really to nothing, however, both the convection and vorticity surrounding this system has increased this morning with the highest vorticity found near 47 West Longitude. Analysis reveals that 93L is moving into a region that is more favorable for development, which lies between 50 and 60 West Longitude. The increase in convection that is being observed this morning is a sign that this disturbance is not dead, however, it is not even close to being a tropical depression either.

The global model guidance as a whole are not too enthusiastic in developing 93L into nothing more than a low pressure system or perhaps a tropical depression as it tracks across the Caribbean later this week. There a few interesting things I found in the model data this morning.

The first is that the 3 km HWRF experimental model forecasts 93L to develop during the day Monday and actually become a tropical storm during the day Tuesday just as it’s approaching the island of Barbados. The 3 km HWRF experimental model then forecasts 93L to track across Barbados on Tuesday night as a tropical storm and then across the Windward Islands early Wednesday morning as a tropical storm.

The second interesting item I found in the model data is that the latest NAM model forecasts 93L to track across the Windward Islands as perhaps a tropical depression at the most during Tuesday.

The final interesting item has to do with the European model, which does not really develop 93L, however, it does forecast the development of a fairly strong tropical cyclone which seems to come from the west coast of Africa within the next 24 to 36 hours. The European model forecasts that this new disturbance to remain weak for the next week and then strengthen fairly quickly as it tracks across the Leeward Islands next Sunday and then tracks across or just north of the Virgin Islands next Monday before being located just east of the Turks and Caicos Islands next Tuesday. Satellite imagery from western Africa showed a rather large tropical disturbance tracking across the country of Mauritania in western Africa and this seems to be where the European model is getting its idea of a strong tropical cyclone from. To be honest, I am very skeptical of the European model forecast given no other agreement among the other model members, however, it will be monitored nevertheless.

Ok, back to Invest 93L and my opinions on it: I do think that Invest 93L will continue to build convection today through Monday as it tracks towards the Windward Islands and Barbados. At this time, I don’t think that this will be a tropical depression or a tropical storm when it reaches Barbados and the Windward Islands during Tuesday and Tuesday night. Even with that, expect strong gusty winds, choppy seas and heavy rainfall across Barbados and the Windward Islands from Tuesday into Wednesday.

Once 93L gets into the Caribbean around the middle part of this week, it will find much warmer ocean temperatures and an environment that is somewhat favorable for development and it seems very possible that this could organize into a tropical depression or a tropical storm as it tracks west-northwestward across the Caribbean during the middle and later parts of this week. What is keeping me from really forecasting robust development is the fact that none of the latest model guidance are really forecasting any development from this disturbance and run it right into Central America next weekend as a weak system.

The overall pattern over the next seven to ten days gives us a couple of possibilities: The weakness in the ridge of high pressure is expected to shift westward into the eastern Gulf of Mexico over the next week or so. If 93L stays weak like the model guidance suggests then it would remain in the Caribbean steered by the low-level flow right into central America or Belize. The second possibility is that if 93L develops into a strong tropical storm or a hurricane, it would “feel” that weakness in the ridge of high pressure and turn northward into the Gulf of Mexico threatening the central and eastern Gulf coast.

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 needs to be watched closely for development this week and this is something that I will be doing; so keep checking back for the latest discussions.

[ROCK]

very good write up I guess....but to bring up the NAM is sort of reaching for something to talk about, IMO....I do not understand his quote that the ridge that has been firmly intact over Texas for months will shift westward? huh? Bro its still here and if anything it will erode east. ..currently the GOM weakness is in the Eastern GOM...I guess it didnt make sense to me...

[KWT]

I think its highly likely this will be a Caribbean runner, I don't think its going to be making a beeline for the gulf, most likely track IMO is into CA and maybe into the BoC before Mexico...

[ROCK]

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_084l.gif

[KWT]

Looks like a nearly identical track to the last NAM run.

GFS coming out pretty soon as well...

[ROCK]

00z ECM is a very good solution providing it does stay weak till about 65-70W...if it looks like its going to develop a little earlier, then it'll be too far south with its solution...

I agree....notice the 06Z GFDL run for 92L shows X93L heading towards the Yucatan...

[ROCK]

you look on the NASA sat views you can see this does have good vort...around 50W right now...

[Sanibel]

Looks like the prevailing negative conditions are still in place no matter where this goes.

[KWT]

00z ECM is a very good solution providing it does stay weak till about 65-70W...if it looks like its going to develop a little earlier, then it'll be too far south with its solution...

I agree....notice the 06Z GFDL run for 92L shows X93L heading towards the Yucatan...

Yeah I suspect most models will take 93L in whatever form towards that general area...

[SETXPTNeches]

very good write up I guess....but to bring up the NAM is sort of reaching for something to talk about, IMO....I do not understand his quote that the ridge that has been firmly intact over Texas for months will shift westward? huh? Bro its still here and if anything it will erode east. ..currently the GOM weakness is in the Eastern GOM...I guess it didnt make sense to me...

Rock - What do you see for us in SETX? We are not that far from each other (as the crow flies).

[KWT]

Looks like the prevailing negative conditions are still in place no matter where this goes.

I think conditions may not be too bad for the system once in the Caribbean, esp in the C/W portion, but till then conditions look negative enough to keep it in check.

Looks like a classic late brewer W.Caribbean/BoC type system to me...

[Rgv20]

NWS Brownsville morning discussion regarding 93L.

LONG TERM.../MONDAY NIGHT THROUGH SATURDAY/,,,HOT..HUMID AND DRY
CONDITIONS WILL CONTINUE AS TEMPS REMAIN A FEW DEGREES ABOVE NORMAL
BUT JUST BELOW RECORD LEVELS. 5H RIDGE CENTERED OVER TEXAS WILL
DRIFT WEST AND BECOME ESTABLISHED OVER THE 4 CORNERS AREA OF THE
SW UNITED STATES BY MID WEEK. RAIN CHANCES REMAIN ALMOST NIL...BUT
NOMINAL 5 PERCENT POPS RETAINED SINCE I CANT RULE OUT SOME VERY
ISOLATED NOCTURNAL CONVECTION WHICH HAS BEEN OCCURRING THE PAST
COUPLE OF NIGHTS OVER THE ADJACENT OFFSHORE WATERS. ALSO CANT RULE
OUT SOME BRIEF AND WEAK SEABREEZE SHOWER DEVELOPMENT ON ANY GIVEN
DAY. LOOKING BEYOND THE WEEKEND...MODELS SUGGEST THE TROPICAL
SYSTEM WHICH WAS ADVERTISED TO ENTER THE GULF EARLY NEXT WEEK HAS
TRENDED MUCH WEAKER AND SEEMS MORE LIKELY TO BE CONFINED TO THE
SOUTHERN GULF IF IT DOES. COULD PROVIDE AN INCREASE IN TROPICAL
MOISTURE ACROSS THE AREA. STILL LOTS OF UNCERTAINTY...SO
MONITORING CONTINUES...

[KWT]

Yep, as they say at the end still plenty of uncertainty with regards to this system and how it evolves over the next 5-7 days.

[Gustywind]

93L

[Ptarmigan]

I am not too quick to write off Invest 93L yet. It is not over when it is over. Nothing should be written off. The Invest that became Don was deactivated and reactivated again. Besides, there is the Caribbean where 93L will be traveling.

[ROCK]

12Z GFS at it again....BOOM!!

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_204l.gif

[ROCK]

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_276l.gif

BRING IT!!!.. ..I spent half the day yesterday watching what little rain spring up all around me...never rained once here in Pearland....last measurable rain was a least a month ago here. Pearland on the verge of water rationing as well as Houston. League City already mandatory rationing...

[BigB0882]

I don't see much on those maps. Is it at the very bottom of the BOC? Doesn't look like much to me and the moisture it brings, which is better than nothing, looks minimal and I seriously doubt would be so wide spread.

[TexWx]

Rock, the "boom" comment...
Am I just looking in the wrong area?

Whatever I'm looking at is slamming into the Yuc..?