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#646346 (Received by flhurricane at: 9:41 PM 19.Nov.2013) TCDAT4 SUBTROPICAL STORM MELISSA DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013 1100 PM AST TUE NOV 19 2013 THE SATELLITE APPEARANCE OF MELISSA IS LESS IMPRESSIVE THAN A FEW HOURS AGO...WITH JUST A SMALL AREA OF CONVECTION FORMING NEAR AND NORTHEAST OF THE CENTER. THE SYSTEM DOES NOT APPEAR TO BE ANY MORE TROPICAL THAN EARLIER...SO IT IS BEING KEPT AS A SUBTROPICAL STORM. THE INITIAL INTENSITY IS LOWERED TO 45 KT IN ACCORDANCE WITH ASCAT DATA AND THE LATEST TAFB SATELLITE ESTIMATE. ALTHOUGH MELISSA IS FORECAST TO MOVE OVER COLDER WATERS SOON...A LARGE INCREASE IN FORWARD SPEED AND SOME NON-TROPICAL FORCING COULD OFFSET THE DECREASING WATER TEMPERATURES. THUS LITTLE CHANGE IN STRENGTH IS FORECAST FOR THE NEXT 48 HOURS...WHICH IS LOWER THAN THE PREVIOUS NHC PREDICTION...AND IS NEAR THE MODEL CONSENSUS. MELISSA COULD STILL BECOME A TROPICAL STORM IN THE NEXT DAY OR SO BEFORE MOVING OVER COLDER WATERS. SOME WEAKENING IS FORECAST AFTER 48 HOURS DUE TO EXTREMELY COLD WATER AND LOSS OF BAROCLINIC FORCING. MELISSA IS EXPECTED TO TRANSITION INTO A POST-TROPICAL CYCLONE WITHIN 36 HOURS DUE TO THE COLDER WATERS...AND INTO AN EXTRATROPICAL CYCLONE IN ABOUT 3 DAYS. THE STORM IS MOVING TO THE NORTHEAST AT ABOUT 15 KT. MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT ON MELISSA ACCELERATING TO THE NORTHEAST AND EAST-NORTHEAST OVER THE NEXT 48H AHEAD OF A LARGE MID-LATITUDE TROUGH. THE LATEST CONSENSUS HAS SHIFTED EASTWARD... AND THE NHC FORECAST FOLLOWS SUIT. THE CYCLONE WILL PROBABLY BE ABSORBED BY A LARGER LOW AND/OR ASSOCIATED FRONTAL SYSTEM WITHIN 96 HOURS...IF NOT SOONER. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 33.6N 52.4W 45 KT 50 MPH 12H 20/1200Z 35.7N 49.2W 45 KT 50 MPH 24H 21/0000Z 38.4N 43.7W 45 KT 50 MPH 36H 21/1200Z 40.8N 37.7W 45 KT 50 MPH...POST-TROPICAL 48H 22/0000Z 43.0N 31.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 23/0000Z 48.0N 25.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 24/0000Z 54.0N 23.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 25/0000Z...DISSIPATED $$ FORECASTER BLAKE |