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| #540475 (Received by flhurricane at: 4:56 PM 05.Sep.2012) TCDAT2 HURRICANE LESLIE DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012 500 PM AST WED SEP 05 2012 THE CIRRUS OUTFLOW OF LESLIE HAS EXPANDED BY MORE THAN 100 NMI TO THE WEST SINCE THE PREVIOUS ADVISORY...INDICATING THAT THE VERTICAL WIND SHEAR AFFECTING THE CYCLONE HAS DECREASED. A BANDING EYE FEATURE HAS BEEN EVIDENT IN VISIBLE SATELLITE IMAGERY SINCE 1700 UTC...BUT A RECENT BURST OF EYEWALL CONVECTION HAS OBSCURED THE EYE. SSMIS AND TRMM MICROWAVE DATA INDICATE A WELL-DEFINED MID-LEVEL EYE HAS DEVELOPED AND A CONCENTRIC EYEWALL CYCLE COULD BE UNDERWAY. THE INITIAL INTENSITY OF 65 KT IS BASED ON SATELLITE INTENSITY ESTIMATES OF T4.0/65 KT FROM TAFB AND SAB...AND AN AVERAGE ADT ESTIMATE OF T4.3/72 KT OVER THE PAST 6 HOURS. THE INITIAL MOTION ESTIMATE REMAINS 360/02 KT. LESLIE HAS WOBBLED SLIGHTLY TO THE NORTHEAST SINCE THE PREVIOUS ADVISORY...BUT THAT ERRATIC MOTION IS LIKELY JUST DUE TO REFORMATION OF THE EYE. THE LATEST GFS FORECAST TRACK HAS SHIFTED A LITTLE TO THE WEST...WHILE THE ECMWF FORECAST HAS SHIFTED TO THE EAST. SINCE THESE TWO MODELS ARE NOW CONVERGING CLOSER TO THE PREVIOUS FORECAST TRACK...THE NEW NHC FORECAST IS JUST AN UPDATE OF THE PREVIOUS ADVISORY...WHICH LIES A LITTLE TO THE EAST OF THE CONSENSUS MODELS TVCA AND TV15. CONDITIONS ARE EXPECTED TO BE FAVORABLE FOR AT LEAST GRADUAL STRENGTHENING TO OCCUR FOR THE NEXT 96 HOURS. COLD WATER UPWELLING BENEATH THE CYCLONE DUE TO ITS VERY SLOW FORWARD SPEED AND THE PRESENCE OF DRY MID-LEVEL AIR LURKING JUST TO THE WEST OF THE CYCLONE MAY LIMIT THE RATE OF INTENSIFICATION. THE GFS-BASED SHIPS AND LGEM MODELS CONTINUE TO HAVE NEGATIVE FEEDBACK ISSUES AS A RESULT OF THE GFS MODEL CREATING A VERY ROBUST HURRICANE...WHICH FURTHER GENERATES SIGNIFICANT 200 MB WARMING AFTER 72 HOURS. THE ECMWF... UKMET...AND HWRF MODELS ALSO CONTINUE TO PRODUCE A STRONG HURRICANE THROUGHOUT THE FORECAST PERIOD. THE OFFICIAL INTENSITY FORECAST IS VERY SIMILAR TO THE PREVIOUS ADVISORY AND REMAINS REMAINS HIGHER THAN MOST OF THE INTENSITY GUIDANCE AFTER 72 HOURS. LESLIE IS A LARGE TROPICAL CYCLONE THAT IS FORECAST TO GROW IN SIZE OVER THE NEXT SEVERAL DAYS. THE WIND FIELD OF THE CYCLONE... COMBINED WITH ITS EXPECTED SLOW MOTION...WILL HELP TO GENERATE LARGE LONG-PERIOD SWELLS THAT WILL PROPAGATE AWAY FROM THE TROPICAL CYCLONE TOWARD BERMUDA AND MUCH OF THE U.S. EAST COAST FOR THE REMAINDER OF THIS WEEK. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 25.9N 62.7W 65 KT 75 MPH 12H 06/0600Z 26.1N 62.8W 70 KT 80 MPH 24H 06/1800Z 26.5N 63.0W 75 KT 85 MPH 36H 07/0600Z 26.8N 63.1W 80 KT 90 MPH 48H 07/1800Z 27.2N 63.4W 85 KT 100 MPH 72H 08/1800Z 29.3N 64.4W 90 KT 105 MPH 96H 09/1800Z 34.0N 64.4W 95 KT 110 MPH 120H 10/1800Z 42.0N 61.0W 85 KT 100 MPH $$ FORECASTER STEWART |
