ATL: INVEST 95L

[wxman57]

Ozonepete and Wxman57:

Nice discussion, guys. I am on a conference call now, so can't type too much, but if one of you guys has a chance, you might want to tell people why the west winds (which are so important in closing off easterly waves into a closed circ) don't matter here!

Totally different set up!

The plane is finding quite a "mess" out there. There is the pre-frontal trof, which the plane crossed several times. There are outflow boundaries from squalls. But there's no LLC. It's common to find SW-WSW winds ahead of cold fronts/trofs in the region, and that's what the plane found. North of the trof, winds are NW-NE. Again, common behind fronts/trofs. There's no convergence toward any center of circulation, just convergence along the trof boundary.

As always, thunderstorms that may eventually get left behind over the Gulf after the post-frontal wind shear diminishes need to be monitored closely for possible TC development. I don't think that'll be the case with this system, though.

[Aric Dunn]

plane is now finding SE across the "boundary" and almost looks like a center pass actually.. the circ maybe becoming more defined.

it is still attached to the trof atm though... would have to break from it.

[wjs3]

First and foremost, I agree with your analysis. I've thought this looks troffy since last night. Has there been vorticity? Sure. At the surface? Maybe--a frontal wave or little eddy spinning up is not out of the questions. Is there a "true" LLC...no, and I don't think there has ever been. Like you, I also think that it could--could--persist and change that, but that's not what we're looking at now.

Back to the West wind thing--just to build on what you are describing more for anyone following, in an easterly wave (like 94L) the typical windshift is SE-NE or SE-E or SSE to NNE across the trof/wave axis (obviously depending on the characteristics of the wave, sharpness of it, orientation, etc.). So the "missing" wind, if you will, is a west wind. That closes off the circulation. That's why everyone gets excited with a west wind in recon on a system in the mid atlantic.

Whole different ball of wax here. The pre-frontal trough has, as you've described (and typically for the synoptic set up), a SW/NW shift across, so, in an imaginary world where we wanted to close off a center, we look for an east wind. Total opposite of our friend the easterly wave.

Whole different synoptics set up than an easterly wave is my point--as some people may wonder why a west wind would be a big deal in recon of 94L, but not here, this is why.

Back to conference call...

[Aric Dunn]

now east winds. also maybe showing up a little on long range radar.. though that is looking up in the mid levels it does however correspond to what recon is now finding.

[Dean4Storms]

I don't see anything from Recon there but a trough and maybe some outflows from convection here or there.

[Dean4Storms]

If it persists over night it could develop an LLC. although it would be a sheared system, not out of the question.

[cycloneye]

Special Tropical Weather Outlook for 95L

SPECIAL TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
520 PM EDT MON AUG 20 2012

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

SPECIAL OUTLOOK ISSUED TO UPDATE DISCUSSION OF THE SYSTEM IN THE
WESTERN GULF OF MEXICO.

THE NATIONAL HURRICANE CENTER HAS ISSUED THE FINAL ADVISORY ON
POST-TROPICAL CYCLONE GORDON...LOCATED OVER THE NORTHEASTERN
ATLANTIC OCEAN EAST-NORTHEAST OF THE AZORES.

AN AREA OF LOW PRESSURE IS LOCATED ABOUT 1000 MILES EAST OF THE
LESSER ANTILLES. WHILE SATELLITE IMAGERY AND BUOY OBSERVATIONS
INDICATE THAT THE CIRCULATION HAS BECOME BETTER DEFINED OVER THE
PAST FEW HOURS...SHOWER AND THUNDERSTORM ACTIVITY REMAINS LIMITED.
ENVIRONMENTAL CONDITIONS REMAIN CONDUCIVE FOR A TROPICAL DEPRESSION
TO FORM DURING THE NEXT DAY OR SO AS THIS LOW MOVES WESTWARD AT 20
TO 25 MPH. THIS SYSTEM HAS A HIGH CHANCE...80 PERCENT...OF BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. THIS SYSTEM COULD
REACH THE LESSER ANTILLES BY WEDNESDAY AND INTERESTS IN THAT AREA
SHOULD MONITOR THE PROGRESS OF THIS DISTURBANCE.

UPDATED...DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
INDICATE THAT SHOWER AND THUNDERSTORM ACTIVITY IN THE WESTERN GULF
OF MEXICO IS ASSOCIATED WITH AN ELONGATED AREA OF LOW PRESSURE AND
WINDS ARE GENERALLY LIGHT. THE SHOWER AND THUNDERSTORM ACTIVITY
REMAINS DISORGANIZED...AND HAS ALSO DIMINISHED SOMEWHAT OVER THE
PAST FEW HOURS. SOME GRADUAL DEVELOPMENT OF THIS SYSTEM IS STILL
POSSIBLE IF IT REMAINS OVER WATER DURING THE NEXT DAY OR TWO. THIS
SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT BEGINS TO DRIFT SLOWLY
WESTWARD.

A TROPICAL WAVE LOCATED SOUTH-SOUTHWEST OF THE CAPE VERDE ISLANDS
CONTINUES TO PRODUCE DISORGANIZED SHOWER ACTIVITY. SOME GRADUAL
DEVELOPMENT IS POSSIBLE OVER THE NEXT FEW DAYS...AND THIS SYSTEM
HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD AT 15 TO 20 MPH.

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

[Zanthe]

...What was the purpose of that update? :l When I saw a special tropical weather outlook from the NHC twitter feed...I thought they might've...changed something.

[fci]

...What was the purpose of that update? :l When I saw a special tropical weather outlook from the NHC twitter feed...I thought they might've...changed something.

I was just going to post the same thing.
This is the second time in the past few weeks where a Special Update was issued to say virtually nothing.
Is it because a Recon Flight went out and they needed to issue the results and didn't want to wait until the next scheduled update at 8:00?
Strange.......
Anybody know why????

[brunota2003]

Most likely just to keep everyone in the know. Like it says at the top, it was issued to update the discussion, to state recon had found no llc, etc.

[CrazyC83]

IMO, that was a wasteful Recon flight; I would have canceled it as it was pretty much obvious there was no LLC. Unless that was a research flight...

[cycloneye]

Stays at 30%.

SHOWER AND THUNDERSTORM ACTIVITY NEAR AN ELONGATED AREA OF LOW
PRESSURE IN THE WESTERN GULF OF MEXICO HAS DIMINISHED DURING THE
PAST FEW HOURS. SOME GRADUAL DEVELOPMENT OF THIS SYSTEM IS STILL
POSSIBLE IF IT REMAINS OVER WATER DURING THE NEXT DAY OR TWO. THIS
SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT DRIFTS SLOWLY WESTWARD.

[brunota2003]

IMO, that was a wasteful Recon flight; I would have canceled it as it was pretty much obvious there was no LLC. Unless that was a research flight...

NOAA does the research flights, but that doesn't mean the wind and radar data can't be used, especially if it does develop into a TC. If anything, we need more flights like this one! Studying pre-TC disturbances might just lead to much improved understanding of them, not to mention you have to study the non-developers with the developers, otherwise you learn nothing. Plus, it helps feed real data into the models, and not just guesses.

[wxman57]

Looks like 95L is pretty much gone now.

[ROCK]

Looks like 95L is pretty much gone now.

yep...time to "bones" this invest, IMO...

[somethingfunny]

Looks like 95L is pretty much gone now.

yep...time to "bones" this invest, IMO...

[tailgater]

Still 30 %
. SHOWER ACTIVITY NEAR AN ELONGATED AREA OF LOW PRESSURE LOCATED OVER
THE FAR WESTERN GULF OF MEXICO HAS CHANGED LITTLE DURING THE PAST
SEVERAL HOURS. SOME GRADUAL DEVELOPMENT OF THIS SYSTEM IS STILL
POSSIBLE IF IT REMAINS OVER WATER DURING THE NEXT DAY OR TWO. THIS
SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT DRIFTS WESTWARD.

Radar out of Brownsville
http://radar.weather.gov/radar.php?prod ... O&loop=yes

[Tampa_God]

Just me, but it looks like the trough is falling apart at the moment. Activity to the west of the invest seems to be diminishing and heading south while the activity to the east seems to have diminished as well.

[Javlin]

Looks like something might be percolating..with speration from the front

http://www.ssd.noaa.gov/goes/east/gmex/flash-vis.html

[ROCK]

the trof is lifting out and with the high over the Texas this should push whatever left overs from 95L into MX.....wish this thing would leave already...we have to watch 96L.....