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#40281 (Received by flhurricane at: 4:31 PM 17.Aug.2005) TCDAT4 TROPICAL STORM IRENE DISCUSSION NUMBER 53 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT WED AUG 17 2005 THE STRONG WESTERLY SHEAR HAS TAKEN ITS TOLL ON IRENE AND THE SYSTEM IS NO LONGER A HURRICANE. AN AVERAGE OF DVORAK NUMBERS FROM THE THREE SATELLITE AGENCIES ALSO SUPPORTS LOWERING THE INTENSITY TO 60 KT FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE HAS PICKED UP TO 050/18...INDICATING THAT THE ACCELERATION OF THE SYSTEM CONTINUES. WATER VAPOR IMAGERY SHOWS A VIGOROUS SHORTWAVE TROUGH EXTENDING FROM THE CANADIAN MARITIMES TO 28N68W THAT IS MOVING RAPIDLY TOWARD IRENE. AS THIS SHORTWAVE TROUGH AND ASSOCIATED SURFACE FRONT SWEEPS OVER IRENE FROM THE WEST...THE STORM IS EXPECTED TO ACCELERATE FURTHER TO THE NORTHEAST IN RESPONSE TO THE INCREASING SOUTHWESTERLY STEERING FLOW. IRENE IS FORECAST TO MOVE OVER SHARPLY LOWER SSTS WITHIN 12 HOURS...NORTH OF 41N LATITUDE. THE CYCLONE SHOULD QUICKLY DECOUPLE OVER THE COOLER WATERS AND BECOME AN EXTRATROPICAL STORM BY 24 HOURS...OR SOONER...AS INDICATED BY THE FSU CYCLONE PHASE ANALYSIS WEB PAGE. BEYOND 24 HOURS...EXTRATROPICAL IRENE SHOULD CONTINUE ACCELERATING IN THE MID-LATITUDE WESTERLIES AND RACE OFF TO THE NORTHEAST TOWARD GREENLAND AND ICELAND. THE OFFICIAL TRACK IS VIRTUALLY IDENTICAL TO THE PREVIOUS FORECAST AND IS GOOD AGREEMENT WITH THE CONSENSUS OF THE TIGHTLY PACKED NHC MODEL GUIDANCE. THE INITIAL 12 FOOT SEA RADII HAVE BEEN EXPANDED OUT TO 200 NM IN THE NE QUADRANT BASED ON A SHIP REPORT FROM VESSEL ELVX2. FORECASTER COBB/PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 17/2100Z 38.5N 56.3W 60 KT 12HR VT 18/0600Z 41.1N 52.9W 55 KT 24HR VT 18/1800Z 47.1N 46.9W 50 KT...EXTRATROPICAL 36HR VT 19/0600Z 55.5N 40.5W 50 KT...EXTRATROPICAL 48HR VT 19/1800Z...ABSORBED |