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| #35624 (Received by flhurricane at: 10:34 PM 26.Jul.2005) TCDAT1 TROPICAL STORM FRANKLIN DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT TUE JUL 26 2005 A CONVECTIVE CLUSTER WITH TOPS OF -70C TO -75C PERSISTS NEAR AND SOUTH OF THE LOW-LEVEL CENTER OF FRANKLIN. SHEAR ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE THAT THE VERTICAL SHEAR HAS DECREASED DURING THE PAST 12 HR...AND THIS IS LIKELY RESPONSIBLE FOR THE CONVECTIVE INCREASE. SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB AND SAB...AND 30 KT FROM AFWA...WHILE A RECENT QUIKSCAT OVERPASS SHOWS RAIN-CONTAMINATED 40 KT VECTORS SOUTHEAST OF THE CENTER. THE INITIAL INTENSITY REMAINS 35 KT AS A COMPROMISE BETWEEN THE VARIOUS ESTIMATES. CIRRUS OUTFLOW FROM THE CONVECTION HAS COVERED THE CENTER...SO THE INITIAL MOTION IS QUITE UNCERTAIN. THE 24 HR MOTION IS 005/4. HOWEVER...THIS PACKAGE WILL USE A 315/2 DRIFT THAT HAS OCCURRED OVER THE PAST SEVERAL HOURS. WATER VAPOR IMAGERY SHOWS A MID/ UPPER-LEVEL RIDGE PASSING NORTH OF FRANKLIN. AS THIS FEATURE MOVES EASTWARD...PRESSURES SHOULD RISE EAST OF BERMUDA AS THEY FALL OVER THE EASTERN U. S. EAST OF THE NEXT TROUGH AND ASSOCIATED COLD FRONT...CURRENTLY OVER THE NORTHERN PLAINS AND GREAT LAKES. LARGE-SCALE MODELS AGREE THAT THESE CHANGES SHOULD COME ABOUT IN 12-24 HR...AND THAT FRANKLIN SHOULD MOVE NORTHWARD IN RESPONSE. THE CYCLONE THEN SHOULD GRADUALLY TURN NORTHEASTWARD AFTER 24-36 HR AND ACCELERATE INTO THE WESTERLIES THROUGH THE REST OF ITS LIFE. THE OFFICIAL FORECAST TRACK AGREES WITH THIS SCENARIO. THE NEW TRACK IS NEAR THE LEFT EDGE OF THE MAIN ENVELOPE OF GUDIANCE...AND SLOWER THAN THE GUIDANCE BASED ON THE RECENT TRACK RECORD OF THE GUIDANCE BEING TOO FAST. IT WOULD NOT BE SURPRISING TO SEE SOME WEST OF NORTH MOTION IN THE FIRST 12 HR OF THE FORECAST PERIOD. THE CURRENT DECREASE IN SHEAR IS OCCURRING AS AN UPPER-LEVEL CYCLONIC SHEAR AXIS FORMS NEAR FRANKLIN...A PATTERN THAT OVERALL IS NOT THAT FAVORABLE FOR STRENGTHENING. LARGE-SCALE MODELS FORECAST THIS FEATURE TO WEAKEN AND MOVE SOUTH OF FRANKLIN IN ABOUT 12-24 HR... WHICH WOULD OPEN ABOUT A 24 HR WINDOW FOR THE STORM TO STRENGTHEN BEFORE IT MOVES NORTH OF THE GULF STREAM. THE INTENSITY FORECAST CALLS FOR MODEST STRENGTHENING TO 40 KT...WHICH IS ABOUT THE MOST THE INTENSITY GUIDANCE IS CURRENTLY FORECASTING. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 27/0300Z 32.4N 68.6W 35 KT 12HR VT 27/1200Z 33.1N 68.6W 35 KT 24HR VT 28/0000Z 34.4N 68.4W 40 KT 36HR VT 28/1200Z 36.0N 67.8W 40 KT 48HR VT 29/0000Z 38.0N 66.5W 40 KT...BECOMING EXTRATROPICAL 72HR VT 30/0000Z 41.5N 61.5W 30 KT...EXTRATROPICAL 96HR VT 31/0000Z...DISSIPATED |
