Invest 90L: Northern Gulf Of Mexico

[srainhoutx]

The convective remnants of Issac as been declared an invest this morning. It looks highly sheared and should head NE over the next several days as it is picked up by the mid latitude trough that will bring our area a cold front on Saturday.

NHC:

A LOW PRESSURE SYSTEM LOCATED ALONG THE COAST OF THE WESTERN FLORIDA
PANHANDLE WILL MOVE SOUTHWARD INTO THE NORTH-CENTRAL GULF OF MEXICO
LATER TODAY. ENVIRONMENTAL CONDITIONS ARE MARGINALLY CONDUCIVE FOR
SOME GRADUAL DEVELOPMENT OF THIS DISTURBANCE AS IT MOVES SOUTHWARD
TO SOUTH-SOUTHWESTWARD AT 5 TO 10 MPH OVER THE NEXT FEW DAYS. THIS
SYSTEM HAS A LOW CHANCE...20 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

[srainhoutx]

Morning e-mail from Jeff:

Tropics remain very active with another tropical storm forming over the Atlantic Ocean.

Leslie:
TS Leslie remains a sheared system with WNW to NW wind shear affecting the circulation as it remains nearly stationary 490 miles SSE of Bermuda. Leslie is trapped in a region of weak steering as high pressure builds to the north of the system for the next 48 hours. After that the high pressure will shift eastward and a trough will approach the US east coast, with Leslie turning northward and increasing in forward speed. On this track the system will pass near Bermuda as a large hurricane. Conditions looks favorable for intensification as the ongoing shear weakens allowing thunderstorms to develop near the center. The current NHC forecast makes Leslie a 75mph hurricane in 36 hours and a 105mph hurricane in 120 hours.

Michael:
New tropical storm forms over the far eastern Atlantic 1190 miles WSW of the Azores Islands. This tiny tropical storm has shown a mass of deep convection to the NE of the low level center suggesting SW wind shear is affecting the system. Condition should gradually become more favorable for development as the shear relaxes and Michael is forecast to become a hurricane in about 3 days as it drifts toward the NNW and then NW on the south side of high pressure passing to its north. Michael is currently no threat to land.

90L:
An area of surface low pressure is currently moving off the coast of the FL panhandle and AL this morning with a large area of showers and thunderstorms noted over the northern Gulf of Mexico from south of Pensacola to just east of New Orleans. A weak, ill defined circulation is noted in coastal radar images south of Pensacola and Mobile. While one could possibly trace this system back to the remains of Isaac, the official word from NHC is that if development does occur it will be a name (Nadine) as the surface low associated with Isaac appears to have dissipated over KY yesterday. This system is drifting toward the S or SSW at 5-10mph and will be over very warm waters and under light shear for the next 36-48 hours. Some development is possible over the next 48 hours and NHC gives the system a 20% chance of developing into a tropical cyclone. While the area will drift southward, steering currents are very weak as the system is located between building high pressure over TX and a trough along the US east coast. By late Friday into this weekend building of the ridge across the western US will favor a deep and strong downstream trough over the E US and this will swing anything that develops over the NC Gulf toward the NE or ENE toward the west coast of FL. There is marginal model support for this system.

[srainhoutx]

[srainhoutx]

Code: Select all

NOUS42 KNHC 051436
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1035 AM EDT WED 05 SEPTEMBER 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
         VALID 06/1100Z TO 07/1100Z SEPTEMBER 2012
         TCPOD NUMBER.....12-109


I.  ATLANTIC REQUIREMENTS 
    

    2. SUSPECT AREA (GULF OF MEXICO)
       FLIGHT ONE --TEAL 71--
       A. 06/1800Z               D. 28.5N 87.8W
       B. AFXXX 01DDA INVEST     E. 06/1730Z TO 06/2130Z
       C. 06/1700Z               F. SFC TO 10,000 FT  

    3. SUCCEEDING DAY OUTLOOK: 
       A. BEGIN 12-HRLY FIXES AT 07/1200Z IF SUSPECT AREA DEVELOPS.
       B. FIX OF TROPICAL STORM LESLIE AT 07/1800Z NEAR 26.6N 63.2W.

[Rip76]

This could have been big ticket a month ago, the trough/cold front this weekend will keep it out of the Western Gulf.

I agree, but how quickly will this form then move.
And when is the front set to come in, Saturday evening?

[Rip76]

This looks to be "about" the area where Alicia came off the coast if I'm not mistaken.

How long did it take Alicia to spin up and get moving, 2 days?

[Portastorm]

Well, if 90L behaves as the early model runs show ... this will be another tease for us in the WGOM. We so desperately need rain ... at least in south central Texas and even more so in the Hill Country. I hate seeing these Gulf systems spin up and keep us in the rear-view mirror.

[srainhoutx]

One thing that raises an eyebrow is the fact that the 12Z GFS lingers the 500mb vort over the Gulf throughout the next week. The ‘front’ is not as strong today as earlier guidance had suggested, but does bring a pre frontal trough offshore and stalls that boundary. The surface reflection does exit off to the ENE in about 80 hours after remaining stationary S of Grand Isle, Louisiana, but an area of disturbed weather appears to linger several hundred miles S of the Middle Texas Coast if the GFS is correct. Yesterday the GFS suggested the surface reflection would be S of the Florida Panhandle, for what it is worth and only lingered for about 48-60 hours before being shunted off to the ENE.

[Portastorm]

One thing that raises an eyebrow is the fact that the 12Z GFS lingers the 500mb vort over the Gulf throughout the next week. The ‘front’ is not as strong today as earlier guidance had suggested, but does bring a pre frontal trough offshore and stalls that boundary. The surface reflection does exit off to the ENE in about 80 hours after remaining stationary S of Grand Isle, Louisiana, but an area of disturbed weather appears to linger several hundred miles S of the Middle Texas Coast if the GFS is correct. Yesterday the GFS suggested the surface reflection would be S of the Florida Panhandle, for what it is worth and only lingered for about 48-60 hours before being shunted off to the ENE.

Thank you! If I had a dollar for every time you talked me off the ledge ... the first round of drinks around here would be on me.

That is a curious development and I look forward to watching with interest. Once we see frontal passage this weekend, high pressure appears to re-develop over Texas and parts of the northern Gulf. I guess there is a sliver of hope.

[Rip76]

Up to 40%

[srainhoutx]

The 12Z Euro sweeps 90L ENE around hour 72.

HPC Diagnostic Discussion: (prior to the 12Z Euro)


...PAIR OF UPPER LOWS INTERACTING NEAR FLORIDA...
...REMNANT MID-LEVEL CIRCULATION OF ISAAC HEADING TO THE GULF
COAST...
...NEW CONVECTIVE LOW MOVING INTO THE GULF OF MEXICO...

PREFERENCE: 12Z GFS/12Z UKMET/00Z ECMWF
CONFIDENCE: BELOW AVERAGE

MODELS SUGGEST SIMILAR SOLUTIONS WITH THE UPPER LOWS INTERACTING
IN THE SOUTHEAST AND WITH DROPPING THE REMNANT ENERGY FROM ISAAC
SOUTHWESTWARD THROUGH THE GULF OF MEXICO. ALSO...ALL GUIDANCE
KEEPS A SURFACE LOW SPINNING OFF THE CENTRAL GULF COAST THROUGH
THE REMAINDER OF THE FORECAST PERIOD. THE 12Z NAM KEEPS THE LOW
CLOSEST TO THE COAST AND IS A BIT OF A WEAK OUTLIER WHEN COMPARED
TO THE 00Z UKMET/ECMWF/CMC. THE 12Z GFS SHIFTED SLIGHTLY
SOUTH/STRONGER WITH THE SURFACE LOW COMPARED TO ITS 06Z RUN...AND
NOW IS IN BETTER AGREEMENT WITH THE LOW CLUSTERING OF THE 12Z
UKMET/12Z CMC/00Z ECMWF AND ENSEMBLE MEMBERS. BY THE END OF THE
FORECAST PERIOD...THE 12Z CMC GETS ON THE STRONGER/SOUTHERN SIDE
OF MODEL CONSENSUS. SEE NATIONAL HURRICANE CENTER (NHC) TROPICAL
WEATHER OUTLOOKS FOR THE LATEST ON ITS TROPICAL CYCLONE FORMATION
POTENTIAL.

[Rip76]

So "No tropics for you."

[srainhoutx]

18Z Tracks & Intensity:

[srainhoutx]

SHOWER ACTIVITY ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE LOCATED
OVER THE NORTH-CENTRAL GULF OF MEXICO HAS NOT BECOME ANY BETTER
ORGANIZED SINCE YESTERDAY...AND IF THIS TREND CONTINUES...THE
RECONNAISSANCE MISSION SCHEDULED FOR LATER TODAY WILL BE CANCELLED.
THIS WEATHER SYSTEM IS DRIFTING SOUTHWARD AND STILL HAS THE
POTENTIAL FOR SOME DEVELOPMENT DURING THE NEXT DAY OR SO BEFORE
ENVIRONMENTAL CONDITIONS BECOME UNFAVORABLE. THIS SYSTEM HAS A
MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS.

[srainhoutx]

12Z Tracks & Intensity:

[Rip76]

Recon is a go for this afternoon.

I think that front needs to hurry..

[srainhoutx]

Recon is a go for this afternoon.

I think that front needs to hurry..

Additional RECON missions have been tasked as well...

Code: Select all

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1130 AM EDT THU 06 SEPTEMBER 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
         VALID 07/1100Z TO 08/1100Z SEPTEMBER 2012
         TCPOD NUMBER.....12-110


I.  ATLANTIC REQUIREMENTS 
    1. SUSPECT AREA (GULF OF MEXICO)
       FLIGHT ONE --TEAL 72--        FLIGHT TWO --TEAL 73--
       A. 07/1200Z                   A. 08/0000Z
       B. AFXXX 0214A CYCLONE        B. AFXXX 0314A CYCLONE
       C. 07/1030Z                   C. 07/2245Z
       D. 27.0N 89.0W                D. 28.0N 88.5W
       E. 07/1130Z TO 07/1530Z       E. 07/2330Z TO 08/0330Z
       F. SFC TO 10,000 FT           F. SFC TO 10,000 FT

    2. HURRICANE LESLIE
       FLIGHT ONE --NOAA 42--        FLIGHT TWO --NOAA 42--
       A. 07/1200Z                   A. 08/0000Z
       B. NOAA2 0212A LESLIE         B. NOAA2 0312A LESLIE
       C. 07/0800Z                   C. 07/2000Z
       D. 26.8N 62.5W                D. 27.3N 62.8W
       E. 07/1100Z TO 07/1330Z       E. 07/2300Z TO 08/0530Z
       F. SFC TO 10,000 FT           F. SFC TO 10,000 FT

    3. SUCCEEDING DAY OUTLOOK: 
       A. CONTINUE 12-HRLY FIXES IF SUSPECT AREA A THREAT.
       B. POSSIBLE FIX OF HURRICANE LESLIE AT 08/1800Z. 
       C. TWO MORE P-3 MISSIONS AGAINST HURRICANE LESLIE.

    4. REMARKS: THE G-IV WILL FLY A RESEARCH MISSION NEAR 
       HURRICANE LESLIE DEPARTING AT 07/2100Z. 

[tireman4]

Where is the front exactly?

[srainhoutx]

Where is the front exactly?

There is a weak boundary across the TX Panhandle, but that is not the front. The main 'front' is just entering the Northern Plains and frankly there may not be enough 'cold air' that actually filters into our region. I really don't expect anything more than what we saw when Helene formed off the NE Mexico Coast last month when that boundary brought some drier air and temps in the mid 60's for a couple of mornings at best.

[Rip76]

Yay, so dry... warm and well, September