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#40370 (Received by flhurricane at: 4:25 AM 18.Aug.2005) TCDAT4 TROPICAL STORM IRENE DISCUSSION NUMBER 55 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT THU AUG 18 2005 IRENE HAS BEEN ACCELERATING RAPIDLY NORTHEASTWARD THE PAST 6 HOURS NOW THAT THE CYCLONE IS FULLY CAUGHT UP IN THE DEEP SOUTHWESTERLY FLOW AHEAD OF AN APPROACHING STRONG MID-LATITUDE EXTRATROPICAL CYCLONE AND ASSOCIATED FRONTAL SYSTEM. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 45 KT AND 55 KT...RESPECTIVELY. HOWEVER...GIVEN THE FASTER FORWARD SPEED...I HAVE OPTED TO MAINTAIN THE INTENSITY AT 60 KT FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS 045/30. THE INITIAL POSITION IS BASED ON CONTINUITY WITH THE PREVIOUS FORECAST TRACK AND EXTRAPOLATION FROM SEVERAL MICROWAVE SATELLITE POSITION ESTIMATES BETWEEN 17/21Z AND 18/02Z. IRENE SHOULD CONTINUE TO ACCELERATE NORTHEASTWARD AT FORWARD SPEEDS OF 35-40 KT...OR HIGHER...THROUGHOUT THE REMAINDER OF THE FORECAST. THIS WILL TAKE THE CYCLONE OVER MUCH COLDER WATER WITHIN THE NEXT FEW HOURS...WHICH SHOULD RESULT IN A RAPID TRANSITION OVER TO A POWERFUL EXTRATROPICAL LOW PRESSURE SYSTEM. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 18/0900Z 41.3N 51.0W 60 KT...BECOMING EXTRATROPICAL 12HR VT 18/1800Z 46.0N 46.1W 55 KT...EXTRATROPICAL 24HR VT 19/0600Z 54.0N 40.0W 50 KT...EXTRATROPICAL 36HR VT 19/1800Z...ABSORBED BY LARGER EXTRATROPICAL LOW |