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#39751 (Received by flhurricane at: 4:52 AM 15.Aug.2005) TCDAT4 HURRICANE IRENE DISCUSSION NUMBER 43 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT MON AUG 15 2005 IRENE REMAINS BENEATH A LARGE UPPER-LEVEL ANTICYCLONE THAT OCCUPIES MOST THE WESTERN ATLANTIC... AND THE HURRICANE IS TAKING ADVANTAGE OF THIS ENVIRONMENT BY SUSTAINING SOME VERY DEEP CONVECTION THAT HAS BECOME INCREASINGLY SYMMETRIC ABOUT THE CIRCULATION CENTER. SUBJECTIVE DVORAK INTENSITY ESTIMATES ARE 65 KT FROM TAFB AND 77 KT FROM SAB... AND A 3-HR AVERAGE ODT ESTIMATE ALSO YIELDS 77 KT. BASED ON THE IMPROVED SATELLITE APPEARANCE COMPARED TO A FEW HOURS AGO... THE ADVISORY INTENSITY IS INCREASED TO 75 KT. THE UPPER-LEVEL OUTFLOW REMAINS WELL-ESTABLISHED... ASIDE FROM SOME RESTRICTION TO THE NORTHWEST SINCE THE HURRICANE IS APPROACHING THE MIDLATITUDE WESTERLIES ON THE NORTHERN SIDE OF THE UPPER-LEVEL ANTICYCLONE. THESE WESTERLIES WILL SOON BE IMPARTING SHEAR ON THE HURRICANE... SO THE WINDOW OF OPPORTUNITY FOR ANY FURTHER STRENGTHENING SHOULD CLOSE IN ABOUT 12 HOURS... AND THIS SHOULD BE FOLLOWED BY A WEAKENING TREND. THE NEW OFFICIAL INTENSITY FORECAST PEAKS AT 80 KT IN 12 HOURS... SIMILAR TO THE SHIPS AND GFDL... THEN FOLLOWS THE SHIPS WEAKENING TREND... EVEN THOUGH THE GFDL INSISTS ON FURTHER STRENGTHENING TO NEAR 90 KT BEFORE IRENE REACHES COOLER WATERS. IRENE CONTINUES TO ROUND THE MID-LEVEL SUBTROPICAL RIDGE CENTERED NEAR BERMUDA... AND THE INITIAL MOTION ESTIMATE IS NOW 035/10. THIS RIDGE IS FORECAST BY THE GLOBAL MODELS TO FLATTEN OUT AS IRENE MOVES TO ITS NORTH DURING THE NEXT 24 HOURS... RESULTING IN MORE ZONAL WESTERLY FLOW THAT SHOULD TURN IRENE MORE TO THE EAST-NORTHEAST DURING THE NEXT COUPLE OF DAYS... GRADUALLY ACCELERATING AWAY FROM THE U.S. EAST COAST. THE GFS REMAINS THE FAST OUTLIER... BUT THE OFFICIAL FORECAST WILL REMAIN CLOSER TO THE DYNAMICAL MODEL CONSENSUS AND THE PREVIOUS ADVISORY. ALONG THE OFFICIAL FORECAST TRACK... IRENE WOULD PASS OVER THE NORTH WALL OF THE GULF STREAM IN ABOUT 48 HOURS... AND IT SHOULD CONTINUE TO WEAKEN THEREAFTER AS AN EXTRATROPICAL SYSTEM OVER COOLER WATERS. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 15/0900Z 36.1N 68.3W 75 KT 12HR VT 15/1800Z 37.0N 66.5W 80 KT 24HR VT 16/0600Z 38.1N 63.8W 75 KT 36HR VT 16/1800Z 39.3N 60.7W 65 KT 48HR VT 17/0600Z 41.3N 57.3W 60 KT 72HR VT 18/0600Z 47.5N 48.0W 50 KT...EXTRATROPICAL 96HR VT 19/0600Z 56.0N 39.0W 40 KT...EXTRATROPICAL 120HR VT 20/0600Z...ABSORBED |