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#631748 (Received by flhurricane at: 10:53 AM 13.Sep.2013) TCDAT4 TROPICAL STORM HUMBERTO DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092013 1100 AM AST FRI SEP 13 2013 VERTICAL SHEAR IS TAKING ITS TOLL ON HUMBERTO. ALL OF THE DEEP CONVECTION HAS BEEN SHEARED AWAY FROM THE CIRCULATION...LEAVING AN EXPOSED CENTER WITH SOME IMPRESSIVE MESOVORTICES. THE INITIAL WIND SPEED IS LOWERED TO 55 KT...BASICALLY AS FAST AS THE DVORAK CONSTRAINTS ALLOW. FURTHER WEAKENING SEEMS PROBABLE FOR THE NEXT DAY OR SO DUE TO INCREASING SOUTHWESTERLY SHEAR AND MARGINAL SSTS. IN A COUPLE OF DAYS...THE VERTICAL WIND SHEAR SHOULD BEGIN TO DIMINISH WHILE HUMBERTO MOVES OVER WARMER WATERS...WHICH COULD ALLOW FOR SOME RESTRENGTHENING. GLOBAL MODELS SUGGEST THAT THE STORM WILL UNDERGO A TROUGH INTERACTION IN THE LONG RANGE...LEAVING IT IN A FAVORABLE ENVIRONMENT TO BECOME EVEN STRONGER. THE OFFICIAL INTENSITY FORECAST IS LOWERED FROM THE PREVIOUS ONE DURING THE FIRST 36 HOURS BASED ON CURRENT TRENDS AND THE RATHER STRONG SHEAR FORECAST. AT THE END OF THE PERIOD...THE NHC FORECAST IS A LITTLE HIGHER...BUT IS STILL BELOW THE MODEL CONSENSUS. THE INITIAL MOTION IS 300/9. A WEST-NORTHWEST TRACK OF HUMBERTO IS EXPECTED FOR THE NEXT COUPLE OF DAYS DUE TO A STRONG RIDGE OVER THE NORTHEASTERN ATLANTIC. THE STORM SHOULD TURN NORTHWARD BY DAYS 4-5 WHILE IT RECURVES AROUND THE WESTERN SIDE OF THE RIDGE. THE ONLY SIGNIFICANT DIFFERENCE IN THE MODEL GUIDANCE IS HOW FAST THE STORM ACCELERATES INTO THE FAR NORTH ATLANTIC OCEAN...WHICH DEPENDS ON WHAT PARTICULAR SHORTWAVE AMPLIFIES THE NEXT MID-LATITUDE TROUGH. THE NEW NHC PREDICTION WILL STAY CLOSE TO THE PREVIOUS ONE...NEAR THE FLORIDA STATE SUPERENSEMBLE AND A BIT FASTER THAN THE DYNAMICAL MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 24.7N 31.3W 55 KT 65 MPH 12H 14/0000Z 25.4N 32.7W 45 KT 50 MPH 24H 14/1200Z 26.3N 35.0W 40 KT 45 MPH 36H 15/0000Z 27.4N 37.3W 40 KT 45 MPH 48H 15/1200Z 28.5N 39.4W 40 KT 45 MPH 72H 16/1200Z 30.7N 42.5W 45 KT 50 MPH 96H 17/1200Z 32.8N 45.0W 55 KT 65 MPH 120H 18/1200Z 36.5N 44.5W 65 KT 75 MPH $$ FORECASTER BLAKE |