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Extratropical Depression Lee


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Very interesting snip from LCH:

TROPICAL STORM LEE CONTINUES TO DISPLAY SUBTROPICAL CHARACTERISTICS...

AS REVEALED IN SATELLITE IMAGERY.

SATELLITE IMAGERY HIGHLIGHTS A VERY LARGE VORTICITY COMMA CLOUD JUST

SOUTHWEST OF MARSH ISLAND...COMPLETE WITH SALIENT DRY SLOT OVER

THE EASTERN QUADRANT OF LEE.

THE GFS MODEL COMPUTES A WARM-TYPE OCCLUSION CYCLONE...COMPLETE

WITH A TROWAL AIRSTREAM MORE TYPICAL OF COOL SEASON DYNAMICS.

BECAUSE LEE IS SO LARGE (A LARGE ROSSBY WAVE)...A GENERAL

DRIFTING MOTION HAS BEEN OBSERVED (FIRST NORTHWARD NOW WESTWARD).

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Very interesting snip from LCH:

TROPICAL STORM LEE CONTINUES TO DISPLAY SUBTROPICAL CHARACTERISTICS...

AS REVEALED IN SATELLITE IMAGERY.

SATELLITE IMAGERY HIGHLIGHTS A VERY LARGE VORTICITY COMMA CLOUD JUST

SOUTHWEST OF MARSH ISLAND...COMPLETE WITH SALIENT DRY SLOT OVER

THE EASTERN QUADRANT OF LEE.

THE GFS MODEL COMPUTES A WARM-TYPE OCCLUSION CYCLONE...COMPLETE

WITH A TROWAL AIRSTREAM MORE TYPICAL OF COOL SEASON DYNAMICS.

BECAUSE LEE IS SO LARGE (A LARGE ROSSBY WAVE)...A GENERAL

DRIFTING MOTION HAS BEEN OBSERVED (FIRST NORTHWARD NOW WESTWARD).

It's looked sub-tropical the entire time, probably one of the main reasons it isn't losing much steam yet despite being half over land. I wonder how they'll handle it in the post-analysis.

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Looks to me based on Lake Charles radar and visible satellite that Lee is having some success in an attempt to wrap around convection south if the COC. Can't help but wonder if this "true" center is not in the process of a cyclonic loop within the larger gyre that results in Lee moving a bit more off-marsh later this evening. Lee still has an opportunity to strengthen some I think.

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A couple of stations very close to the center, albeit non-NWS, are suggesting the minimum pressure is around 986 mb. Given that the radar and satellite presentations are still healthy, I think Lee is still on a strengthening trend.

I see an eye on radar. There aren't 2 centers anymore. Good thing this isn't over SE LA

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A couple of stations very close to the center, albeit non-NWS, are suggesting the minimum pressure is around 986 mb. Given that the radar and satellite presentations are still healthy, I think Lee is still on a strengthening trend.

Yep. Lee appears to still be deepening.

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From NESDIS:

SATELLITE PRECIPITATION ESTIMATES..DATE/TIME 09/03/11 2206Z

SATELLITE ANALYSIS BRANCH/NESDIS---NPPU---TEL.301-763-8678

LATEST DATA USED: GOES-EAST:2155Z JS

.

LOCATION...NW FLORIDA/SW ALABAMA/S MISSISSIPPI/LOUISIANA...

LOCATION...E TEXAS...

.

ATTN WFOS...MOB...JAN...LIX...LCH...SHV...HGX...

ATTN RFCS...SERFC...LMRFC...WGRFC...

.

EVENT...LOW LEVEL CENTER OF LEE MOVING TO THE NW NOW RIGHT ON SW LA

COAST. HEAVIEST RAINS TO THE NW OF THE CENTER AS WELL AS WITH BANDS

WRAPPING TO THE NW ACROSS S MS/SW AL/FAR NW FL.

.

SATELLITE ANALYSIS AND TRENDS...VISIBLE ANIMATION THROUGH 2155Z SHOWS

THE WELL DEFINED LOW LEVEL CENTER OF LEE VERY CLOSE TO THE COAST OF SW

LA NEAR S VERMILLION PARRISH WITH AN APPARENT SLIGHT WESTWARD WOBBLE IN

THE FEATURE SEEN IN VISIBLE IMAGERY. A SIGNIFICANT EXPANSION OF COLDER

CLOUD TOPS HAS RECENTLY BEEN NOTED WITH A BAND TO THE NW OF THE CENTER

OVER SW LA WHERE SATELLITE ESTIMATED RATES ARE NEAR 1.5"/HALF HOUR. HAVE

ALSO SEEN RECENT 3 HOUR OBSERVED METAR TOTALS ENDING AT 21Z OF 1.25"

TO AROUND 1.5" ACROSS W CENT AND SW LA. VIS/IR IMAGERY AND COMPOSITE

RADAR DATA SHOW THIS AREA OF MODERATE TO HEAVY RAIN HAS SPREAD FARTHER TO

THE WEST ACROSS THE TX/LA BORDER INTO E AND SE TX. TO THE EAST, VISIBLE

IMAGERY INDICATES THE DRY SLOT HAS WRAPPED AROUND FROM SE INTO S CENT LA

WITH BREAKS IN THE CLOUDS SEEN. SOME CONVECTION HAS FORMED IN THE DRY

SLOT DURING THE AFTERNOON, BUT THE BULK OF THE MORE INTENSE BANDS HAVE

FOCUSED ON AREAS TO THE EAST OVER S MS/SW AL/FAR NW FL. IN THIS REGION,

3 HOURLY METAR OBSERVED TOTALS ANS SATELLITE ESTIMATES ARE SHOWING 1-2"

TOTALS WITH ISOLATED SPOTS NEAR 3" AND POSSIBLY HIGHER.

.

AN ANNOTATED SATELLITE GRAPHIC SHOWING THE HEAVY PRECIPITATION THREAT AREA

SHOULD BE AVAILABLE ON THE INTERNET ADDRESS LISTED BELOW IN APPROXIMATELY

10-15 MINUTES.

.

SHORT TERM OUTLOOK VALID 2145-0045Z...MEDIUM TO HIGH CONFIDENCE FACTOR IN

SHORT TERM OUTLOOK...SATELLITE IMAGERY AND TRENDS POINT TOWARD THE RECENT

FLARE UP OVER SW LA AS WELL AS THE CONTINUATION OF BANDS SPREADING INLAND

OVER S MA/SW AL/FAR NW FL AS THE PRIMARY HEAVY RAINFALL THREAT AREAS FOR

THE NEXT 2-3 HOURS. CONCERN EXISTS FOR ADDITIONAL INTENSE BANDS TO FORM

TO THE NW AND N OF THE LOW LEVEL CENTER OF LEE RESULTING IN VERY INTENSE

RAIN RATES AND SIGNIFICANT TOTALS ACROSS SW TO S CENT LA. TO THE EAST,

SEE NO REAL LET UP IN THE PERSISTENT BANDS MOVING INLAND OVER S MS/SW

AL/FAR NW FL AS VISIBLE IMAGERY STILL SHOWS WELL DEFINED OVERSHOOTING

TOPS OFFSHORE SPREADING NORTHWARD TOWARD THE COAST. ADDITIONAL TOTALS

OF AT LEAST 1-3" ARE LIKELY IN THIS REGION DURING THE NEXT 2-3 HOURS.

post-32-0-32021900-1315094216.gif

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The 18z GFDL defects and joins the NAM ranks.

Parts of Texas would gladly take the 18z GFDL, though it does reduce the amount of rain associated with the system before landfall, likely for similar reasons as Don's vanishing act.

Otherwise, a fair number of the 18z GFS ensembles take the system Southeast initially, though none with a westward motion.

at201113_ensmodel.gif

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Parts of Texas would gladly take the 18z GFDL, though it does reduce the amount of rain associated with the system before landfall, likely for similar reasons as Don's vanishing act.

Otherwise, a fair number of the 18z GFS ensembles take the system Southeast initially, though none with a westward motion.

at201113_ensmodel.gif

The EC doesn't really show a SE motion, but it just kind of drifts it around for a good 24-36 hours before moving it just N of due E. It does not really show it gaining much latitude until it gets to MS/AL.

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I'm so bored that I'm sitting here looping radar to see if the rain gets into Houston. :) I'm rooting for the NAM because its more interesting than a decaying TS over land and it may be more conducive to letting Katia make it further west.

It would be a coup for the NAM but I'm not sure it can be discounted given that the system is well within range and not at the edges of its areal coverage.

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The EC doesn't really show a SE motion, but it just kind of drifts it around for a good 24-36 hours before moving it just N of due E. It does not really show it gaining much latitude until it gets to MS/AL.

Just FWIW, the GFS EnKF and FIMY both show Lee making a bit of a cyclonic loop similar to what it looks like it's doing now, and moving back over the Gulf before turning NE across SE LA and into SE MS and W AL. Actually look fairly similar to the EC, only they seem to get a little farther S before going NE.

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Galveston is getting mighty close to TS conditions:

Wind  from the NNW (330 degrees) at 35 MPH (30 KT) gusting to 44 MPH (38 KT)  
Visibility  10 mile(s)  
Sky conditions  overcast  
Precipitation last hour  0.07 inches  
Temperature  81.0 F (27.2 C)  
Dew Point  69.1 F (20.6 C)  
Relative Humidity  67%  
Pressure (altimeter)  29.56 in. Hg (1001 hPa)  

ob KGLS 040052Z AUTO 33030G38KT 10SM OVC085 27/21 A2956 RMK AO2 PK WND 35041/0025 SLP010 P0007 T02720206

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I'm so bored that I'm sitting here looping radar to see if the rain gets into Houston. :) I'm rooting for the NAM because its more interesting than a decaying TS over land and it may be more conducive to letting Katia make it further west.

I don't have much faith in it outside 24 hours or so. I'd actually probably rather it be wrong so I get something up here but it's a cool solution should it come to pass which it would still be pretty hard not to doubt at this point.

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Galveston is getting mighty close to TS conditions:

Wind  from the NNW (330 degrees) at 35 MPH (30 KT) gusting to 44 MPH (38 KT)  
Visibility  10 mile(s)  
Sky conditions  overcast  
Precipitation last hour  0.07 inches  
Temperature  81.0 F (27.2 C)  
Dew Point  69.1 F (20.6 C)  
Relative Humidity  67%  
Pressure (altimeter)  29.56 in. Hg (1001 hPa)  

ob KGLS 040052Z AUTO 33030G38KT 10SM OVC085 27/21 A2956 RMK AO2 PK WND 35041/0025 SLP010 P0007 T02720206

The center looks like it has drifted SW based on observational data, and is probably offshore. It certainly seems to be SW of the oil platform KVNP which is reporting a SE wind with an SLP of 988.5 mb. Some of the strongest winds are definitely occurring on the NW side of the system, with a platform S of KLCH reporting 50 kt sustained (obviously at a substantial elevation, but still).

One other note of interest - looks to be several supercells developing in the mid level dry slot due S of the MS Gulf Coast.

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The center looks like it has drifted SW based on observational data, and is probably offshore. It certainly seems to be SW of the oil platform KVNP which is reporting a SE wind with an SLP of 988.5 mb. Some of the strongest winds are definitely occurring on the NW side of the system, with a platform S of KLCH reporting 50 kt sustained (obviously at a substantial elevation, but still).

One other note of interest - looks to be several supercells developing in the mid level dry slot due S of the MS Gulf Coast.

Yes I was just about to post this..a SW wobble based on that platform reading..

it looks like an occluding low (as LCH pointed out) but around the center things wrapping up now just south of the county line

so a warm core occluding low over water still

interesting

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A piece is kind of breaking off and getting entangled with the front moving by, while the low level center drifts south southwest deeper into the Gulf.

In Ivan (I think) back in 2004, something sort of like that happened...low level swirl detached from the developing extra tropical low around NC or VA and did a bizarre loop back down into the Gulf, while the ET low drenched the Northeast and exited into the North Atlantic.

The 00Z NAM continues to advertise a WSW motion...

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