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| #39714 (Received by flhurricane at: 10:34 PM 14.Aug.2005) TCDAT4 HURRICANE IRENE DISCUSSION NUMBER 42 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SUN AUG 14 2005 AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT ON A TEST FLIGHT MEASURED STRONG ENOUGH WINDS AT 850 MB TO JUSTIFY UPGRADING IRENE TO A HURRICANE. PEAK FLIGHT LEVEL WINDS WERE 88 KT...WHICH IN FACT CORRESPONDS TO ABOUT 70 KT AT THE SURFACE...AND THAT IS THE ASSIGNED ADVISORY INTENSITY. IRENE HAS GOOD OUTFLOW TO THE NORTHEAST...ALTHOUGH THE WESTERLIES ARE BEGINNING TO IMPINGE ON THE NORTHWEST QUADRANT. IRENE WILL BE OVER WARM WATERS FOR ANOTHER 24 HOURS OR SO...AND SO SOME ADDITIONAL STRENGTHENING IS POSSIBLE. GLOBAL MODELS SUGGEST THAT THE SHEAR SHOULD INCREASE SHARPLY AFTER THAT TIME AS WELL. IRENE IS LIKELY TO BECOME EXTRATROPICAL AND MERGE WITH A LARGER BAROCLINIC LOW LATE IN THE FORECAST PERIOD. THE INITIAL MOTION IS 025/10. IRENE HAS ROUNDED THE SUBTROPICAL RIDGE AND WILL SOON BE DEFLECTED TO THE RIGHT BY THE MID-LATITUDE WESTERLIES. THE FLOW IS FAIRLY ZONAL HOWEVER...AND IF IRENE TURNS SHARPLY TO THE RIGHT IT MAY TAKE A LITTLE WHILE FOR ANY RAPID ACCELERATION TO OCCUR. THE OFFICIAL FORECAST SHOWS ONLY A MODEST ACCELERATION UNTIL A SIGNIFICANT MID-LATITUDE TROUGH APPROACHES IN ABOUT 72 HOURS. THERE IS CONSIDERABLE VARIATION IN THE SPEED OF THE GUIDANCE MODELS...WITH THE GFS BEING THE FASTEST. THE OFFICIAL FORECAST IS NOT NEARLY THAT FAST...BUT IS FAIRLY CLOSE TO THE PREVIOUS ADVISORY AND IS NEAR THE FSU SUPERENSEMBLE. IRENE BECOMES THE SEASON'S THIRD HURRICANE. THE NORMAL NUMBER OF HURRICANES FORMED BY THIS DATE IS ONE. ONLY ONE YEAR...1966... HAD MORE HURRICANES FORMED BY THIS POINT IN THE SEASON. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 15/0300Z 35.3N 69.2W 70 KT 12HR VT 15/1200Z 36.4N 67.8W 75 KT 24HR VT 16/0000Z 37.6N 65.1W 70 KT 36HR VT 16/1200Z 38.8N 62.2W 60 KT 48HR VT 17/0000Z 40.0N 59.0W 55 KT 72HR VT 18/0000Z 45.0N 51.0W 50 KT...EXTRATROPICAL 96HR VT 19/0000Z 54.0N 40.0W 40 KT...EXTRATROPICAL 120HR VT 20/0000Z...ABSORBED |
