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#630974 (Received by flhurricane at: 4:59 PM 10.Sep.2013) TCDAT2 TROPICAL STORM GABRIELLE DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 500 PM AST TUE SEP 10 2013 AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING GABRIELLE FOUND PEAK SFMR WINDS OF 45-50 KT NORTHWEST AND SOUTHEAST OF THE CENTER ON THEIR FIRST PASS THROUGH THE STORM...AND THE INITIAL INTENSITY IS INCREASED TO 50 KT FOR THIS ADVISORY. THE CENTRAL PRESSURE OF 1004 MB IS BASED ON A DROPSONDE FROM THE AIRCRAFT. GABRIELLE HAS BEEN ABLE TO STRENGTHEN TODAY DESPITE THE PRESENCE OF MODERATE SOUTHWESTERLY SHEAR WHICH HAS EXPOSED THE LOW-LEVEL CENTER TO THE SOUTHWEST OF THE DEEP CONVECTION. WHILE MODERATE SHEAR IS EXPECTED TO CONTINUE OR EVEN INCREASE OVER THE NEXT COUPLE OF DAYS...THE STATISTICAL/DYNAMICAL AND GLOBAL MODELS SHOW SOME STRENGTHENING DURING THAT TIME. THIS SEEMS TO BE SUPPORTED BY MARGINAL SSTS AND AN INCREASE IN UPPER-LEVEL DIVERGENCE AHEAD OF A MID/UPPER-LEVEL TROUGH. THE NHC FORECAST SHOWS THE POTENTIAL FOR SOME STRENGTHENING AND THEN LITTLE CHANGE THROUGH EXTRATROPICAL TRANSITION IN ABOUT 96 HOURS. THE INITIAL MOTION ESTIMATE IS 360/09. THE MODEL GUIDANCE SHOWS A TURN TOWARD THE NORTH-NORTHWEST WITH A DECREASE IN FORWARD SPEED OVER THE NEXT 12 TO 24 HOURS...AS GABRIELLE IS TUGGED WESTWARD BY A WEAKENING MID/UPPER-LEVEL LOW CURRENTLY SITUATED EAST OF FLORIDA. AT 48 HOURS AND BEYOND...AN ACCELERATION TOWARD THE NORTHEAST IS EXPECTED AHEAD OF A DEEP-LAYER TROUGH MOVING THROUGH EASTERN NORTH AMERICA. THE TRACK MODELS REMAIN IN REASONABLE AGREEMENT ON THE OVERALL SCENARIO...HOWEVER MUCH OF THE GUIDANCE HAS SHIFTED A LITTLE TO THE LEFT THIS CYCLE. OVERALL...THE NHC TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE THROUGH 48 HOURS AND AFTERWARD HAS BEEN ADJUSTED A BIT TO THE LEFT...BUT STILL LIES EAST OF THE MULTI-MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 31.5N 64.9W 50 KT 60 MPH 12H 11/0600Z 32.6N 65.0W 55 KT 65 MPH 24H 11/1800Z 33.5N 65.5W 55 KT 65 MPH 36H 12/0600Z 34.3N 66.0W 55 KT 65 MPH 48H 12/1800Z 35.7N 66.5W 55 KT 65 MPH 72H 13/1800Z 42.0N 63.5W 55 KT 65 MPH 96H 14/1800Z 52.0N 52.4W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 15/1800Z...DISSIPATED $$ FORECASTER BRENNAN |