ATL: ISAAC - Post-Tropical - Discussion

[ConvergenceZone]

RAOBS (upper air soundings) across the Lesser Antilles indicate 25-30kt easterly flow just above the surface and very dry air in the mid levels. This indicates that 94L will continue to struggle with low-level speed shear (not upper-level shear) along with dry air. May be a less than 50% chance it will become a TS east of the islands. Will likely cause a few heavy squalls with wind gusts to 50-60 mph as it is now (assuming a few more squalls develop) when it passes the islands on Wednesday. Center should reach the islands Wednesday morning.

Wxman, thanks for your analysis. Do you think it will finally have the chance to become a
depression once it gets west of the islands? or are the conditions as such that it might
just remain as a wave even once it gets west of the islands?

Wow, where is all of this dry air and shear coming from this year???

[Aric Dunn]

Could see another burst of convection over the next couple hours. the low level cloud deck has thickened some.

[cpdaman]

aric what's ur take on the LLC seems it's been a bit erratic over last hour or so ....jumping nw ...gettin pulled back sw at 1515 frame....opening...closing...reforming? or am i just seeing things

[Aric Dunn]

aric what's ur take on the LLC seems it's been a bit erratic over last hour or so ....jumping nw ...gettin pulled back sw at 1515 frame....opening...closing...reforming? or am i just seeing things

well without convection its going to wobble around. best to just focus on the overall circ and not the exact center.

[Sanibel]

These naked systems can change in a hurry once they hit recurve. Chris in reverse.

[Weatherboy1]

I just don't see a strong likelihood 94 falls apart completely given the very large circulation envelope, the relatively well-defined pattern, and so on. Struggle to develop? Yes. Eventually develop once it gets further west? I also believe the answer there is yes, vs. falling apart completely like other "naked swirl" systems have done in the past.

[TreasureIslandFLGal]

Why are storms moving fast this year and having a hard time developing?

When the Atlantic ridge is strong, it results in moving systems along its periphery pretty quickly. Weaker ridging doesn't quite get the speedy circulation around it that drives these storms westward as fast.

That is good and bad as far as US mainland hits go. It tends to keep systems weaker in the beginning, as their strength can't ramp up due to the forward speed-induced sheer keeping them in check. However, such strong ridges also tend to not allow the quick recurves that take things safely out to sea. So when the storms finally get all the way across and reach the southwestern periphery of the High, where they finally can slow down and gain strength, they are then so close to the CONUS that they pose a very serious threat if the steering patterns could then allow them to head poleward. They could then have time to strengthen and hit. Sure, they may need to start as a Tropical Storm, rather than already being a long tracking hurricane, but they are now better "positioned" to head towards a potential US strike.
Best case, is that when they finally do arrive at the far western edge of the ridge, that conditions ahead are hostile and they are forced to remain weak, and never get a chance to ramp up at all. That's when they simply keep flowing westward or wnw as waves or weak storms to bring beneficial rains.

[GCANE]

Boundary-layer inversion is holding back sustained convection

http://rammb.cira.colostate.edu/product ... 7_TANO.GIF

[MGC]

Looking bad this early afternoon.....I would think the NHC lowers the chances of 48 hour development...MGC

[Blown Away]

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MIAMI FL
939 AM EDT MON AUG 20 2012

LONG TERM...[WEDNESDAY-WEEKEND]
QUITE A BIT OF UNCERTAINTY BECOMES INTRODUCED AS WE APPROACH THE
WEEKEND DUE TO A CONSIDERABLE AMOUNT OF VARIANCE WITHIN THE LATEST
MODEL PACKAGE. THIS AMOUNT OF UNCERTAINTY WILL KEEP THE FORECAST
CONFIDENCE LOW AS A RESULT THROUGH THIS TIME. THE MAIN INTEREST
THROUGH THIS PERIOD WILL REMAIN ON WHAT IS CURRENTLY AN AREA OF
INTEREST WELL EAST OF THE LESSER ANTILLES THAT COULD BECOME A
TROPICAL CYCLONE OVER THE UPCOMING 24-48 HRS. WHILE SOME OF THE
INDIVIDUAL MODELS TAKE THIS AREA OF INTEREST DUE WEST ACROSS THE
CARIBBEAN SEA...THE GFS AND ITS ENSEMBLE MEAN SOLUTIONS INDICATE A
NORTH AND NORTHWEST TURN ACROSS CUBA OVER THE WEEKEND. DUE TO THE
AMOUNT OF LOW CONFIDENCE THROUGH THIS TIME...WILL CONTINUE TO
INDICATE MAINLY MORE OF A SEASONAL RAINFALL FORECAST WITH
SCATTERED AFTERNOON SHRA/TSTMS EACH DAY AND CONTINUE TO MONITOR
THE LATEST MODEL GUIDANCE OVER THE UPCOMING DAYS AS CONFIDENCE
SHOULD GRADUALLY BEGIN TO INCREASE.

NWS Miami starting to chew on 94L a little.

[tolakram]

A couple of saved HiRes visibles.

14:45Z


16:15Z

[cpdaman]

love the definition in those visibles ....do you have the time stamp that goes with them by chance. LLC tightness looks good in last shot, (older?) thank you

[CrazyC83]

With the large circulation, if this does get going, it could be a dangerous flood threat for an extremely large area.

Personal Forecast Disclaimer:
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.

[tolakram]

love the definition in those visibles ....do you have the time stamp that goes with them by chance. LLC tightness looks good in last shot, (older?) thank you

Editing post to add timestamps.

[tolakram]

saved loop

[Blown Away]

If it was 80% at 8am, IMO no reason to lower or raise the %.

[SouthFLTropics]

It appears that the engine is cranking but that it just may have some bad fuel (i.e. SAL, Dry Air) right now. Their is clearly a vigorous circulation evident on satellite and if it gets some better fuel I think it will take off. It needs to mix out the garbage right now and also try and slow down. The engine is basically flooded at the moment.

SFT

[hurricaneCW]

These storms can definitely be a problem down the road. 94L has a nice and large circulation and once it finds a more favorable environment, it can rapidly take off.

[adam0983]

The Long range models are showing invest 94L heading toward the United States. I know that these models are not accurate. Does anyone still see invest 94L being a fish storm?

[cycloneye]

Something is going on that the NHC site is not working for the past hour. That is why there is no 2 PM TWO yet.