|
Show Selection: |
| #539186 (Received by flhurricane at: 10:47 PM 31.Aug.2012) TCDAT2 TROPICAL STORM LESLIE DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012 1100 PM AST FRI AUG 31 2012 LESLIE IS PRODUCING A LARGE CENTRAL AREA OF CONVECTION WITH CLOUD TOPS COLDER THAN -80C. HOWEVER...AN SSM/IS OVERPASS AT 2318 UTC AND A TRMM OVERPASS AT 0030 UTC INDICATED THAT THE CENTER IS STILL DISPLACED TO THE NORTH OF THE CONVECTION DUE TO CONTINUING NORTHERLY VERTICAL WIND SHEAR. SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB AND 45 KT FROM SAB....AND THE INITIAL INTENSITY REMAINS 55 KT. ALTHOUGH SHEAR CONTINUES...THE CIRRUS OUTFLOW IS GOOD IN ALL DIRECTIONS EXCEPT TO THE NORTH. THE INITIAL MOTION IS 295/18. THE SUBTROPICAL RIDGE NORTH AND NORTHEAST OF THE STORM SHOULD STEER LESLIE WEST-NORTHWESTWARD FOR THE NEXT 36 HR. AFTER THAT...THE CYCLONE IS LIKELY TO TURN NORTHWESTWARD AND THEN NORTHWARD DUE TO A BREAK IN THE RIDGE CREATED BY A DEVELOPING MID/UPPER-LEVEL LEVEL LOW PRESSURE SYSTEM...CURRENTLY SEEN IN WATER VAPOR IMAGERY BETWEEN BERMUDA AND THE EASTERN UNITED STATES. THE FORECAST TRACK THROUGH 72 HR IS AN UPDATE OF THE PREVIOUS TRACK AND LIES NEAR THE CENTER OF THE TRACK GUIDANCE ENVELOPE. THE GUIDANCE DIVERGES AFTER 72 HR AS LESLIE IS EXPECTED TO MOVE INTO AN AREA OF LIGHT STEERING CURRENTS. THE GFS...GFDL...HWRF...AND CANADIAN MODELS SHOW A SLOW EASTWARD OR NORTHEASTWARD MOTION DURING THIS PERIOD...WHILE THE ECMWF AND THE FLORIDA STATE SUPERENSEMBLE SHOW A SLOW NORTHWESTWARD MOTION. OVERALL...THE GUIDANCE ENVELOPE HAS SHIFTED A LITTLE TO THE EAST AFTER 72 HR. AS A RESULT...THE NEW FORECAST TRACK IS ALSO NUDGED A LITTLE TO THE EAST AND SHOWS A SLOW NORTHWARD MOTION BY 120 HR. HOWEVER...IT LIES ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE TO THE WEST OF THE CONSENSUS MODELS. THE GLOBAL MODELS SUGGEST THAT SOME NORTHERLY SHEAR SHOULD PERSIST FOR THE NEXT 24-48 HR...AND IT IS UNCLEAR IF LESLIE WILL FIND A REALLY FAVORABLE ENVIRONMENT FOR DEVELOPMENT DURING THIS TIME. FROM 48-96 HR...THE CYCLONE MOVES NORTH OF AN UPPER-LEVEL RIDGE AND IS LIKELY TO ENCOUNTER MODERATE/STRONG WESTERLY SHEAR...WHICH AT THE VERY LEAST SHOULD STOP DEVELOPMENT. THE UPPER-LEVEL WINDS MAY BECOME MORE FAVORABLE AFTER 96 HR...ALTHOUGH THE ECMWF STILL SHOWS A RATHER HOSTILE ENVIRONMENT DURING THIS TIME. THE NEW INTENSITY FORECAST IS THE SAME AS THE PREVIOUS FORECAST...CALLING FOR SLOW DEVELOPMENT THROUGH 48 HR...LITTLE CHANGE IN STRENGTH AT 72 AND 96 HR...AND SLIGHT STRENGTHENING FROM 96-120 HR. THE FORECAST IS A BLEND OF THE SHIPS MODEL AND THE INTENSITY CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 17.4N 52.8W 55 KT 65 MPH 12H 01/1200Z 18.3N 54.8W 60 KT 70 MPH 24H 02/0000Z 19.7N 57.4W 60 KT 70 MPH 36H 02/1200Z 21.1N 59.4W 65 KT 75 MPH 48H 03/0000Z 22.6N 60.9W 70 KT 80 MPH 72H 04/0000Z 25.0N 62.0W 70 KT 80 MPH 96H 05/0000Z 26.5N 62.5W 70 KT 80 MPH 120H 06/0000Z 28.0N 62.5W 75 KT 85 MPH $$ FORECASTER BEVEN |
