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Tropical Storm LEE (Text)

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TROPICAL STORM LEE DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132011
1000 AM CDT SUN SEP 04 2011
 
SURFACE OBSERVATIONS AND WSR-88D RADAR DATA INDICATE THAT LEE
FINALLY MOVED INLAND OVER SOUTH-CENTRAL LOUISIANA THIS MORNING
AROUND 11Z ABOUT 10 NMI SOUTH OF INTRACOASTAL CITY. RECENT DOPPLER
RADAR DATA INDICATE BANDS OF CONVECTION HAVE FORMED OVER
SOUTHEASTERN LOUISIANA AND NEAR THE FLORIDA PANHANDLE AND EXTEND
SOUTHWESTWARD OVER THE GULF OF MEXICO. SOME OF THESE BANDS HAVE
CONTAINED DOPPLER VELOCITIES OF 65-72 KT FROM 8000-12000 FT IN
35-45 DBZ ECHOES...WITH MEAN VALUES OF AT LEAST 60 KT. ALTHOUGH
THESE DOPPLER VELOCITY VALUES WOULD TYPICALLY EQUATE TO SURFACE
WINDS OF 50-55 KT...THE SHORT-LIVED NATURE OF THESE NEW CONVECTIVE
BANDS SUGGESTS THAT ANY HIGHER WIND SPEEDS WILL LIKELY BE VERY
TRANSIENT. THE INITIAL INTENSITY IS BEING MAINTAINED AT 40 KT BASED
ON WIND REPORTS FROM NOAA BUOY 42040...BUT THE GUST DIFFERENTIAL IN
THE FORECAST/ADVISORY PRODUCT HAS BEEN INCREASED TO 55 KT FROM THE
STANDARD 50-KT GUST VALUE IN ORDER TO ACCOUNT FOR THE STRONGER
DOPPLER VELOCITIES THAT HAVE BEEN OBSERVED.

LEE IS DRIFTING SLOWLY TO THE NORTHEAST...OR 040/03 KT. THERE IS NO
SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK REASONING. LEE IS
EXPECTED TO REMAIN EMBEDDED IN A WEAK STEERING FLOW REGIME FOR THE
NEXT 24 HOURS OR SO AND ONLY DRIFT SLOWLY EAST-NORTHEASTWARD TO
NORTHEASTWARD. AFTER THAT...A VIGOROUS SHORTWAVE TROUGH IS
FORECAST TO DIG SOUTHEASTWARD FROM THE NORTHERN AND CENTRAL PLAINS
AND GRADUALLY LIFT LEE NORTHEASTWARD AT A FASTER FORWARD SPEED...
BUT STILL AT LESS THAN 10 KT. BY 48 HOURS...LEE IS EXPECTED TO MERGE
WITH A FAIRLY BRISK FRONTAL SYSTEM FOR THIS TIME OF THE YEAR...AND
BECOME A LARGE SLOW-MOVING EXTRATROPICAL LOW PRESSURE SYSTEM OVER
THE TENNESSEE VALLEY. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE
PREVIOUS ADVISORY...EXCEPT THAT THE FORWARD SPEED WAS DECREASED
AFTER 48 HOURS...AND CLOSELY FOLLOWS THE CONSENSUS TRACK MODELS...
TVCN AND TVCA.
 
LEE WILL BE MOVING OVER THE RAIN-SATURATED FLAT TERRAIN OF SOUTHERN
AND SOUTHEASTERN LOUISIANA TODAY...WITH A LARGE PORTION OF THE
CIRCULATION REMAINING OVER WATER. AFTERNOON HEATING SHOULD ALSO
GENERATE DEEP CONVECTION OVER LAND AND NEAR THE CENTER OF
CIRCULATION...WHICH COULD ADD SOME ENERGY TO THE CYCLONE. AS A
RESULT...THE TROPICAL STORM IS EXPECTED TO WEAKEN MORE SLOWLY
THAN INDICATED BY THE TYPICAL INLAND DECAY RATE FOR INLAND TROPICAL
CYCLONES. 
 
SINCE HEAVY RAINS...STRONG WINDS...AND THE HIGHEST STORM SURGE
VALUES ARE OCCURRING VERY FAR FROM THE CENTER...IT IS IMPORTANT NOT
TO FOCUS ON THE EXACT LOCATION OF THE CENTER OF LEE. THE PRIMARY 
THREAT FROM LEE WILL BE EXTREMELY HEAVY RAINFALL OVER MUCH OF THE
SOUTHEASTERN U.S. DURING NEXT SEVERAL DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/1500Z 29.9N  91.9W   40 KT  45 MPH...INLAND
 12H  05/0000Z 30.1N  91.5W   35 KT  40 MPH...INLAND
 24H  05/1200Z 30.6N  90.4W   30 KT  35 MPH...INLAND
 36H  06/0000Z 31.4N  88.9W   30 KT  35 MPH...INLAND
 48H  06/1200Z 32.6N  87.5W   30 KT  35 MPH...POST-TROP/EXTRATROP
 72H  07/1200Z 34.5N  86.5W   20 KT  25 MPH...POST-TROP/EXTRATROP
 96H  08/1200Z 36.5N  86.0W   20 KT  25 MPH...POST-TROP/EXTRATROP
120H  09/1200Z...DISSIPATED
 
$$
FORECASTER STEWART
 
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