000 WTNT43 KNHC 030857 TCDAT3 TROPICAL STORM LEE DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132011 400 AM CDT SAT SEP 03 2011 SURFACE AND AIRCRAFT DATA INDICATE THAT LEE HAS STRENGTHENED A LITTLE DURING THE PAST SEVERAL HOURS WITH THE MAXIMUM WINDS NOW NEAR 45 KT AND A CENTRAL PRESSURE NEAR 995 MB. THE CYCLONE CONTINUES TO HAVE AN ELONGATED CENTER OF CIRCULATION AND A LARGE RADIUS OF MAXIMUM WINDS...AND THIS...COMBINED WITH THE GENERAL APPEARANCE IN SATELLITE IMAGERY...SUGGESTS THAT LEE HAS AT LEAST SOME CHARACTERISTICS OF A SUBTROPICAL CYCLONE. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SUGGEST THE STORM IS EXPERIENCING ABOUT 15 KT OF WESTERLY VERTICAL WIND SHEAR DUE TO INTERACTION WITH AN UPPER-LEVEL TROUGH VERY CLOSE TO THE SYSTEM...AND WATER VAPOR IMAGERY SHOWS MID/UPPER-LEVEL DRY AIR OVER THE SOUTHWESTERN QUADRANT OF THE STORM. THE CENTER HAS TENDED TO REFORM FROM TIME TO TIME...WHICH MAKES THE INITIAL MOTION OF 345/6 RATHER UNCERTAIN. MOST TRACK MODEL GUIDANCE NOW AGREES THAT LEE SHOULD MOVE SLOWLY FOR THE NEXT 48 HR AS A RIDGE TO THE NORTH SLOWLY WEAKENS...FIRST GENERALLY NORTHWARD INTO SOUTHERN LOUISIANA AND THEN GENERALLY NORTHEASTWARD. AFTER 48 HR...A DEEP-LAYER TROUGH APPROACHING FROM THE NORTH SHOULD CAUSE A FASTER MOTION TOWARD THE NORTHEAST...ALTHOUGH THERE REMAINS SOME SIGNIFICANT DISAGREEMENT BETWEEN THE MODELS ON THE EXACT SPEED. THE NEW FORECAST TRACK IS SHIFTED A LITTLE TO THE WEST OF THE PREVIOUS TRACK BASED ON THE CURRENT POSITION AND MOTION...THEN LIES NORTH OF THE PREVIOUS TRACK FROM 36 HOURS ONWARD. GIVEN THAT THE CURRENT ISSUES WITH SHEAR AND DRY AIR HAVE NOT YET SIGNIFICANTLY AFFECTED DEVELOPMENT...LEE IS EXPECTED TO CONTINUE STRENGTHENING UNTIL LANDFALL. WEAKENING AFTER LANDFALL IS LIKELY TO BE SLOWER THAN NORMAL TO THE THE MARSHY NATURE OF THE LOUISIANA COAST AND THE AMOUNT OF THE CIRCULATION THAT SHOULD REMAIN OVER WATER. LATER IN THE FORECAST PERIOD...LEE IS FORECAST TO MERGE WITH AN ONCOMING COLD FRONT AND BECOME EXTRATROPICAL...A SOMEWHAT UNUSUAL OCCURRENCE IN THIS AREA AT THIS TIME OF YEAR. IT SHOULD BE NOTED THAT THE WINDS AND RAINS OF LEE EXTEND FAR FROM THE CENTER...SO IT IS IMPORTANT NOT TO FOCUS TOO MUCH ON THE EXACT FORECAST TRACK. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 28.8N 91.9W 45 KT 50 MPH 12H 03/1800Z 29.3N 92.0W 50 KT 60 MPH 24H 04/0600Z 30.0N 91.9W 55 KT 65 MPH...INLAND 36H 04/1800Z 30.5N 91.5W 45 KT 50 MPH...INLAND 48H 05/0600Z 31.0N 90.7W 40 KT 45 MPH...INLAND 72H 06/0600Z 32.5N 88.5W 35 KT 40 MPH...INLAND 96H 07/0600Z 35.0N 86.0W 25 KT 30 MPH...POST-TROP/EXTRATROP 120H 08/0600Z 37.0N 82.5W 20 KT 25 MPH...POST-TROP/EXTRATROP $$ FORECASTER BEVEN