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| #35434 (Received by flhurricane at: 10:37 PM 25.Jul.2005) TCDAT1 TROPICAL STORM FRANKLIN DISCUSSION NUMBER 19 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT MON JUL 25 2005 FRANKLIN HAS UNDERGONE ANOTHER STRUCTURAL CHANGE THIS EVENING. A NEW VORTICITY CENTER APPEARED FROM UNDER THE CONVECTION EAST OF THE MAIN CIRCULATION CENTER...AND IT AND THE MAIN CENTER ARE ROTATING AROUND EACH OTHER. THE CENTER TRACKED EARLIER IS CURRENTLY THE MOST INVOLVED WITH CONVECTION...SO THAT CENTER POSITION IS USED IN THIS ADVISORY. HOWEVER...THE APPEARANCE OF THE SECONDARY VORTICITY CENTER SUGGESTS THE POSSIBILITY THAT THE OVERALL SYSTEM MAY REFORM DURING THE NEXT DAY OR SO...OR THAT A MEAN CIRCULATION CENTER MAY BECOME MORE APPROPRIATE FOR TRACKING. THE INITIAL INTENSITY REMAINS 35 KT BASED ON SATELLITE ESTIMATES OF 35 KT FROM TAFB AND AFWA...AND 30 KT FROM SAB. THE INITIAL MOTION IS AN ERRATIC AND UNCERTAIN 090/7. ON THE LARGE SCALE...THE STEERING IS FAIRLY STRAIGHTFORWARD. A MID-LATITUDE SHORTWAVE TROUGH AND ASSOCIATED COLD FRONT ARE PASSING NORTH OF FRANKLIN. OVER THE NEXT 48 HR...PRESSURES SHOULD RISE EAST OF THE STORM IN THE WAKE OF THE TROUGH AND FALL TO THE WEST IN ADVANCE OF THE NEXT STRONGER TROUGH. THIS SUGGESTS FRANKLIN SHOULD TURN NORTHWARD DURING THAT TIME...FOLLOWED BY ACCELERATION NORTHEASTWARD INTO THE WESTERLIES. ALL MODEL GUIDANCE...INCLUDING THE BAM MODELS...IS NOW IN GOOD AGREEMENT WITH THIS SCENARIO. HOWEVER... SUPERIMPOSED ON TOP OF THIS WILL BE CYCLOIDAL MOTION OF THE CENTER INSIDE THE LARGER CYCLONIC ENVELOPE...AS WELL AS POSSIBLE RE-FORMATION OF THE CENTER DUE TO MERGER WITH THE SECONDARY VORTICITY CENTER OR TO CONVECTIVE BURSTS. THUS...THE ERRATIC MOTION SEEN FOR THE LAST 24-30 HR WILL LIKELY CONTINUE...STARTING WITH THE CENTER TAKING A NORTHWARD TURN DURING THE NEXT FEW HOURS AS THE SECONDARY CENTER MOVES TO ITS WEST. A CONVECTIVE BURST IS NEAR THE PRIMARY CENTER RIGHT NOW...AND WATER VAPOR IMAGERY SUGGESTS A SMALL UPPER-LEVEL LOW HAS FORMED NEAR FRANKLIN. THIS MAY PROVIDE TEMPORARY PROTECTION FROM THE SHEAR. HOWEVER...LARGE-SCALE MODELS FORECAST THIS LOW TO GET PUSHED AWAY FROM THE STORM BY STRONG NORTHWESTERLY UPPER-LEVEL FLOW...WHICH IS CURRENTLY SEEN APPROACHING FRANKLIN IN WATER VAPOR IMAGERY. THE GFS FORECASTS A VERY HOSTILE ENVIRONMENT DURING THE NEXT 48 HR...WITH STRONG SHEAR AND A NEW UPPER-LEVEL CYCLONIC SHEAR AXIS FORMING NEAR THE STORM. THE UKMET AND NOGAPS SHOW A LESS HOSTILE ENVIRONMENT...BUT EVEN THEY TAKE 48 HR OR MORE TO SHOW CONDITIONS THAT MIGHT ALLOW STRENGTHENING. THUS...THE INTENSITY FORECAST WILL CONTINUE TO CALL FOR GRADUAL DECAY. THERE IS A POSSIBILITY THAT CONVECTIVE BURSTS COULD CAUSE SOME TEMPORARY STRENGTHENING IN THE SHEAR ENVIRONMENT. FRANKLIN HAS SHIFTED FARTHER EAST THAN PREVIOUSLY FORECAST...SO A TROPICAL STORM WATCH IS BEING ISSUED FOR BERMUDA AT THIS TIME. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 26/0300Z 30.7N 68.2W 35 KT 12HR VT 26/1200Z 31.3N 67.8W 35 KT 24HR VT 27/0000Z 32.0N 67.5W 35 KT 36HR VT 27/1200Z 33.0N 67.3W 35 KT 48HR VT 28/0000Z 34.0N 67.2W 30 KT 72HR VT 29/0000Z 36.5N 65.5W 25 KT...DISSIPATING 96HR VT 30/0000Z 40.5N 60.5W 25 KT...REMNANT LOW 120HR VT 31/0000Z...DISSIPATED |
