ATL: INVEST 90L - Discussion

[chaser1]

Still too broad to try and make out a LLC yet; looks to me like the overall broad circulation seems to be ENE - WSW oriented. Does appear that perhaps a more dynamic mid level feature (?) might be dropping to the SW, and presently on the coast or maybe just offshore near Ft. Walton Beach. Seems like the greater convergence is certainly offshore between Mobile and Pensacola, as previously stated. Most dynamic models seem to keep 90L around in the Gulf for at least 4 days. Its hard to imagine that we wouldn't at least get a named storm out of this, especially given the calander! Heck, one Sept 7th some years ago, I was on a Caribbean cruise and accidentally "spit" overboard.... and even IT developed into a tropcal storm LOL.

Am really curious how far this could really dive south; I just cannot see that much of a steering mechanism to cause it to drop much in latitude. Perhaps it will eventually move eastward and come in around Crystal River, Fla.

[Dean4Storms]

Some models are hinting at this feature becoming trapped under the Ridge behind the trough over southern Florida and then coming back west again toward the Gulf.

[jlauderdal]

I dont believe the Low has moved over water as of yet, per the wind map and the fact that we are dead calm here in pensacola. Not even a hint of wind.

radar might be a good tool to use in this case, just a thought

[cycloneye]

Up to 40%

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT WED SEP 5 2012

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

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON RECENTLY
UPGRADED HURRICANE LESLIE...LOCATED ABOUT 465 MILES SOUTH-SOUTHEAST
OF BERMUDA... AND ON TROPICAL STORM MICHAEL...LOCATED ABOUT 1125
MILES WEST-SOUTHWEST OF THE AZORES.

A LOW PRESSURE SYSTEM IS LOCATED OVER THE EXTREME NORTH-CENTRAL
GULF OF MEXICO...ABOUT 25 MILES SOUTHEAST OF PENSACOLA FLORIDA.
SHOWERS AND THUNDERSTORMS HAVE CONTINUED TO DEVELOP NEAR AND TO
THE SOUTH OF THE CENTER...AND ENVIRONMENTAL CONDITIONS ARE EXPECTED
TO BE AT LEAST MARGINALLY CONDUCIVE FOR SOME GRADUAL DEVELOPMENT
OF THIS DISTURBANCE OVER THE NEXT FEW DAYS. THIS SYSTEM HAS A
MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS AS IT MOVES SOUTHWARD TO SOUTH-SOUTHWESTWARD AT
5 TO 10 MPH. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT IS
SCHEDULED TO INVESTIGATE THE SYSTEM THURSDAY AFTERNOON...IF
NECESSARY

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

$$
FORECASTER STEWART

[jlauderdal]

40 seems conservative, i bet we are up to 80 by bedtime(bedtime is a moving target which allows my prediction an excellent chance of verifying)

Up to 40%

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT WED SEP 5 2012

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

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON RECENTLY
UPGRADED HURRICANE LESLIE...LOCATED ABOUT 465 MILES SOUTH-SOUTHEAST
OF BERMUDA... AND ON TROPICAL STORM MICHAEL...LOCATED ABOUT 1125
MILES WEST-SOUTHWEST OF THE AZORES.

A LOW PRESSURE SYSTEM IS LOCATED OVER THE EXTREME NORTH-CENTRAL
GULF OF MEXICO...ABOUT 25 MILES SOUTHEAST OF PENSACOLA FLORIDA.
SHOWERS AND THUNDERSTORMS HAVE CONTINUED TO DEVELOP NEAR AND TO
THE SOUTH OF THE CENTER...AND ENVIRONMENTAL CONDITIONS ARE EXPECTED
TO BE AT LEAST MARGINALLY CONDUCIVE FOR SOME GRADUAL DEVELOPMENT
OF THIS DISTURBANCE OVER THE NEXT FEW DAYS. THIS SYSTEM HAS A
MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS AS IT MOVES SOUTHWARD TO SOUTH-SOUTHWESTWARD AT
5 TO 10 MPH. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT IS
SCHEDULED TO INVESTIGATE THE SYSTEM THURSDAY AFTERNOON...IF
NECESSARY

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

$$
FORECASTER STEWART

[Stormcenter]

Satellite clearly shows the area the NHC is referring to in their afternoon TWO. IMO


http://weather.rap.ucar.edu/satellite/d ... uration=10

[chaser1]

40 seems conservative, i bet we are up to 80 by bedtime(bedtime is a moving target which allows my prediction an excellent chance of verifying)

What seems bizarre is A) What my eyes see B) That this is the first week of September C) The general dynamics (outside of perhaps slight westerly shear?) seem generally favorable YET -

3 Global models just do not see 90L developing? Hard for me to bet against that. I'm gonna guess 50%-60% tops, by the time I go to bed , and I go to be very very late.

[superstareporter]

I dont believe the Low has moved over water as of yet, per the wind map and the fact that we are dead calm here in pensacola. Not even a hint of wind.

radar might be a good tool to use in this case, just a thought

Why would that be better when we are looking for surface winds, correct? Radar only shows precipitation, so what if there is no precip?

[Stormcenter]

I don't bet on models. I'd be broke by now if I did.

40 seems conservative, i bet we are up to 80 by bedtime(bedtime is a moving target which allows my prediction an excellent chance of verifying)

What seems bizarre is A) What my eyes see B) That this is the first week of September C) The general dynamics (outside of perhaps slight westerly shear?) seem generally favorable YET -

3 Global models just do not see 90L developing? Hard for me to bet against that. I'm gonna guess 50%-60% tops, by the time I go to bed , and I go to be very very late.

[tropicwatch]

Some buoy readings from the area.

Station PCLF1
NOS
Location: 30.403N 87.212W
Date: Wed, 5 Sep 2012 17:30:00 UTC

Winds: ESE (120°) at 1.9 kt gusting to 5.1 kt
Atmospheric Pressure: 29.87 in
Air Temperature: 83.3 F
Water Temperature: 83.3 F

Station 42012
NDBC
Location: 30.065N 87.555W
Date: Wed, 5 Sep 2012 17:50:00 UTC

Significant Wave Height: 3.6 ft
Dominant Wave Period: 5 sec
Mean Wave Direction: WSW (247°)
Atmospheric Pressure: 29.84 in and falling
Air Temperature: 79.0 F
Dew Point: 75.4 F
Water Temperature: 82.4 F

Station PPTA1
Dauphin Island Sea Lab
Location: 30.279N 87.556W
Date: Wed, 5 Sep 2012 17:30:00 UTC

Winds: NNE (30°) at 4.1 kt
Atmospheric Pressure: 29.88 in
Air Temperature: 82.9 F

[Extratropical94]

18Z Best track update - continuing its SSW movement

AL, 90, 2012090518, , BEST, 0, 300N, 870W, 25, 1010, LO

[Hammy]

I'm not quite sure what to make of this still, but just to point out, none of the models saw Michael developing prior either...

[chaser1]

Some buoy readings from the area.

Significant Wave Height: 3.6 ft
Dominant Wave Period: 5 sec
Mean Wave Direction: WSW (247°)
Atmospheric Pressure: 29.84 in and falling
Air Temperature: 79.0 F
Dew Point: 75.4 F
Water Temperature: 82.4 F

So, would speculate that 90L might currently be around 1009mb now? I don't think the GFS shows any forecast maps of it being any lower than 1006mb.
oops, late post here; just saw "Best Track" an hour ago showing 1010mb.

[Tireman4]

Well that is it. I am done. Amazing. I have no idea about anything. I am going back to bed. Remenants of Isaac, El Nino, Models not picking up tropical systems...just color me lost....LOL

[Agua]

That feature came through eastern coastal Mississippi last night and produced the most impressively continuous thunder I have any memory of ever experiencing. Literally, rolling thunder, non stop, for 45 minutes minimum. It could have been much longer but that is how long it continued after it woke me up.

[tropicwatch]

People here keep telling me what a down pour we had last night, I didn't hear a thing. Must have been into cutting some severe logs at the time.

[wxman57]

I can clearly see an LLC on surface obs near the coast at the AL/FL border. 1010mb. Strong northerly shear produced by an upper low over the northern Bahamas is keeping convection south of the center. Shear should drop in 48 hrs, then increase again in 72 hrs as a cold front approaches. About a 24hr window of development Fri PM-Sat PM. I'd give it a 70% chance of becoming a sheared TS before it merges with the front on Sunday and tracks across the northern FL peninsula. Rain threat, not a surge or wind threat. Remember, NHC probabilities are only for the next 48hrs, not for the life of the system.

[psyclone]

I can clearly see an LLC on surface obs near the coast at the AL/FL border. 1010mb. Strong northerly shear produced by an upper low over the northern Bahamas is keeping convection south of the center. Shear should drop in 48 hrs, then increase again in 72 hrs as a cold front approaches. About a 24hr window of development Fri PM-Sat PM. I'd give it a 70% chance of becoming a sheared TS before it merges with the front on Sunday and tracks across the northern FL peninsula. Rain threat, not a surge or wind threat. Remember, NHC probabilities are only for the next 48hrs, not for the life of the system.

that sounds like a reasonable estimate. hopefully the system is accelerating so it doesn't dump too much rain. this could dump on the Debby zone and that region remains wet.

[jlauderdal]

I can clearly see an LLC on surface obs near the coast at the AL/FL border. 1010mb. Strong northerly shear produced by an upper low over the northern Bahamas is keeping convection south of the center. Shear should drop in 48 hrs, then increase again in 72 hrs as a cold front approaches. About a 24hr window of development Fri PM-Sat PM. I'd give it a 70% chance of becoming a sheared TS before it merges with the front on Sunday and tracks across the northern FL peninsula. Rain threat, not a surge or wind threat. Remember, NHC probabilities are only for the next 48hrs, not for the life of the system.

that sounds like a reasonable estimate. hopefully the system is accelerating so it doesn't dump too much rain. this could dump on the Debby zone and that region remains wet.

SE Florida real wet too, SW flow for the next 5-7 days could mean more trouble..T-storms in progress this afternoon

[tbstorm]

I for one am hoping for a nice severe weather outbreak for FL when the whole thing comes through.