[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 040842
TCDAT3

TROPICAL STORM LEE DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132011
400 AM CDT SUN SEP 04 2011

SURFACE OBSERVATIONS AND WSR-88D RADAR DATA INDICATE THAT LEE IS
VERY NEAR THE SOUTHERN COAST OF LOUISIANA.  THE INTENSITY HAS BEEN
REDUCED TO 40 KT WHICH IS A LITTLE ABOVE ALL AVAILABLE SUSTAINED
SURFACE WIND OBSERVATIONS...ALTHOUGH SOMEWHAT HIGHER WINDS ARE
STILL OCCURRING AT ELEVATED PLATFORMS IN THE GULF OF MEXICO.  LEE
WILL BE MOVING OVER THE FLAT TERRAIN OF EXTREME SOUTHERN LOUISIANA
TODAY...WITH A LARGE PORTION OF THE CIRCULATION REMAINING OVER
WATER.  THEREFORE...THE CYCLONE IS FORECAST TO WEAKEN MORE SLOWLY
THAN INDICATED BY THE TYPICAL INLAND DECAY RATE...AND THE INTENSITY
FORECAST IS A LITTLE ABOVE THE LATEST LGEM GUIDANCE.  BY 48 HOURS OR
SOONER...THE GFS AND ECMWF MODELS SHOW THE SYSTEM EMBEDDED WITHIN A
FRONTAL ZONE...AND THE OFFICIAL FORECAST SHOWS EXTRATROPICAL
TRANSITION TO HAVE OCCURRED BY THAT TIME.  BASED ON GUIDANCE FROM
THOSE SAME GLOBAL MODELS...DISSIPATION IS LIKELY AFTER 96 HOURS.

THE CURRENT MOTION IS A NORTHWARD DRIFT OR ABOUT 360/2.  LEE IS IN A
COL REGION OF THE MID-TROPOSPHERIC FLOW...I.E. WITHIN VERY WEAK
STEERING CURRENTS...AT THIS TIME.  A TROUGH OVER THE NORTH-CENTRAL
U.S. IS FORECAST TO DIG SOUTHEASTWARD OVER THE NEXT DAY OR SO.  THE
FLOW ON THE SOUTHERN SIDE OF THE TROUGH IS EXPECTED TO TURN THE
TROPICAL CYCLONE TOWARD THE NORTHEAST AND EAST-NORTHEAST DURING THE
NEXT 24 TO 36 HOURS.  LATER IN THE PERIOD...THE POST-TROPICAL
CYCLONE SHOULD TURN TO THE LEFT AS IT MOVES ON THE SOUTHEAST SIDE
OF THE TROUGH.  THE OFFICIAL TRACK FORECAST IS JUST A LITTLE TO THE
SOUTH OF THE PREVIOUS ONE DURING THE FIRST COUPLE OF DAYS AND VERY
SIMILAR THEREAFTER.  THIS IS ALSO FAIRLY CLOSE TO THE GFS FORECAST.

SINCE HEAVY RAINS AND STRONG WINDS EXTEND VERY FAR FROM THE
CENTER...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT LOCATION OF THE
CENTER OF LEE.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0900Z 29.6N  92.5W   40 KT  45 MPH
 12H  04/1800Z 30.0N  92.3W   35 KT  40 MPH...INLAND
 24H  05/0600Z 30.3N  91.5W   30 KT  35 MPH...INLAND
 36H  05/1800Z 30.8N  90.1W   30 KT  35 MPH...INLAND
 48H  06/0600Z 32.0N  88.4W   30 KT  35 MPH...POST-TROP/EXTRATROP
 72H  07/0600Z 34.5N  86.0W   20 KT  25 MPH...POST-TROP/EXTRATROP
 96H  08/0600Z 37.0N  84.0W   20 KT  25 MPH...POST-TROP/EXTRATROP
120H  09/0600Z...DISSIPATED

$$
FORECASTER PASCH



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