[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 030257
TCDAT3

TROPICAL STORM LEE DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132011
1000 PM CDT FRI SEP 02 2011

SATALLITE...SURFACE...AND RECONNAISSANCE AIRCRAFT DATA INDICATE THAT
LEE HAS BEEN MOVING SLOWLY NORTHWARD THIS EVENING.  THE CENTER IS
LOCATED TO THE SOUTHWEST OF A BURST OF DEEP CONVECTION THAT
DEVELOPED LATE THIS AFTERNOON AND HAS BEEN EXPANDING IN SIZE THIS
EVENING.  WIND REPORTS FROM BUOYS AND OIL RIGS OVER THE GULF AND
DATA FROM THE AIRCRAFT INDICATE THAT INTENSITY OF THE TROPICAL
STORM REMAINS AROUND 40 KT.

LEE IS CURRENTLY LOCATED TO THE SOUTHWEST OF A MID-LEVEL RIDGE THAT
IS CENTERED OVER THE OHIO VALLEY.  THIS RIDGE IS FORECAST TO WEAKEN
AND SLIDE EASTWARD DURING THE NEXT DAY OR SO...AS A MID-LATITUDE
TROUGH MOVES INTO THE NORTH-CENTRAL UNITED STATES.  THIS SHOULD
ALLOW LEE TO MOVE SLOWLY NORTHWARD DURING THE NEXT 24-36 HOURS. AS
THE TROUGH PASSES NORTH OF THE TROPICAL STORM IN 36-48 HOURS...THE
MODELS SUGGEST THAT LEE WILL SLOW DOWN AND MEANDER NEAR OR OVER
SOUTHERN LOUISIANA.  AFTER THAT TIME...THE TROUGH IS FORECAST TO
INTERACT WITH THE CYCLONE AND LEE SHOULD MOVE NORTHEASTWARD AT A
FASTER FORWARD SPEED AND BECOME EXTRATROPICAL LATE IN THE PERIOD.
THE MODEL GUIDANCE IS IN GENERAL AGREEMENT WITH THIS SCENARIO...
HOWEVER THERE ARE SOME LARGE DIFFERENCE IN THE FORWARD SPEED OF LEE
ESPECIALLY AFTER 48 HOURS.  THE NEW OFFICIAL FORECAST IS A BLEND OF
THE GFS AND ECMWF MODELS AND IS A LITTLE FASTER THAN THE PREVIOUS
ADVISORY...MAINLY DUE TO THE MORE NORTHWARD INITIAL POSITION.  IT
IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK OF LEE...SINCE
TROPICAL STORM CONDITIONS AND HEAVY RAINFALL EXTEND WELL AWAY OF
THE CENTER.

A SMALL UPPER-LEVEL LOW TO THE NORTHWEST OF LEE CONTINUES TO
IMPART ABOUT 15-20 KT OF SOUTHWESTERLY SHEAR OVER THE TROPICAL
CYCLONE.  THIS UPPER-LOW IS FORECAST TO WEAKEN DURING THE NEXT
12-24 HOURS...WHICH SHOULD PROVIDE A MORE FAVORABLE UPPER AIR
ENVIRONMENT AND ALLOW FOR GRADUAL STRENGTHENING.  THE NHC INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY THROUGH LANDFALL AND
IS IN GOOD AGREEMENT WITH THE SHIPS/LGEM GUIDANCE.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0300Z 28.2N  91.6W   40 KT  45 MPH
 12H  03/1200Z 28.6N  91.6W   50 KT  60 MPH
 24H  04/0000Z 29.4N  91.5W   55 KT  65 MPH
 36H  04/1200Z 30.0N  91.3W   50 KT  60 MPH...INLAND
 48H  05/0000Z 30.2N  91.0W   45 KT  50 MPH...INLAND
 72H  06/0000Z 31.5N  89.0W   40 KT  45 MPH...INLAND
 96H  07/0000Z 34.0N  87.0W   25 KT  30 MPH...POST-TROP/EXTRATROP
120H  08/0000Z 35.5N  86.0W   20 KT  25 MPH...POST-TROP/EXTRATROP

$$
FORECASTER BROWN


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