000 WTNT44 KNHC 232053 TCDAT4 HURRICANE IRENE DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011 500 PM EDT TUE AUG 23 2011 THE EYE OF IRENE WAS MORE APPARENT IN VISIBLE SATELLITE IMAGERY EARLY THIS AFTERNOON...BUT HAS RECENTLY BECOME OBSCURED. THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT FOUND A MAXIMUM 700 MB FLIGHT-LEVEL WIND OF 74 KT AND PEAK SFMR WINDS OF AROUND 75 KT. IT HAS BEEN NEARLY 24 HOURS SINCE THE AIRCRAFT HAS MEASURED WINDS THAT SUPPORT AN INTENSITY OF 85 KT. THEREFORE...THE INITIAL INTENSITY HAS BEEN REDUCED TO 80 KT. THE PRESSURE DROPPED ABOUT A MILLIBAR ON EACH SUCCESSIVE FIX AND WAS DOWN TO 976 MB ON THE LASS PASS AROUND 1830 UTC. ANOTHER HURRICANE HUNTER AIRCRAFT WILL INVESTIGATE IRENE THIS EVENING. THE HURRICANE WILL BE TRAVERSING VERY WARM WATERS DURING THE NEXT COUPLE OF DAYS. HOWEVER...THE UPPER-LEVEL PATTERN IS NOT IDEAL FOR RAPID DEVELOPMENT...AND THE GLOBAL MODELS SUGGEST MODERATE WESTERLY SHEAR WILL CONTINUE FOR ANOTHER DAY OR TWO. THE NEW INTENSITY FORECAST IS SLIGHTLY BELOW THE PREVIOUS ADVISORY DURING THE FIRST 24 HOURS DUE TO THE LOWER INITIAL INTENSITY. AFTER THAT...IT IS UNCHANGED FROM THE PREVIOUS FORECAST AND BRINGS IRENE TO MAJOR HURRICANE STATUS IN 36 HOURS. THE NEW INTENSITY FORECAST IS A BLEND OF THE LOWER STATISTICAL GUIDANCE AND THE MORE AGGRESSIVE GFDL/HWRF MODELS. THE AIRCRAFT FIXES INDICATE THAT IRENE HAS BEEN MOVING WEST-NORTHWEST OR 295/8 KT...A LITTLE SLOWER THAN BEFORE. THE TRACK FORECAST REASONING REMAINS UNCHANGED. IRENE IS EXPECTED TO TURN NORTHWESTWARD THEN NORTHWARD DURING THE NEXT 2-3 DAYS AS THE WESTERN PORTION OF THE SUBTROPICAL RIDGE WEAKENS. THE TRACK GUIDANCE IS IN REMARKABLY GOOD AGREEMENT DURING THIS TIME AND THERE IS HIGH CONFIDENCE IN THAT PORTION OF THE FORECAST. AFTER THAT... IRENE IS FORECAST TO MOVE NORTHWARD TO NORTHEASTWARD AROUND THE ATLANTIC RIDGE. SEVERAL OF THE MODELS...INCLUDING THE GFS...ECMWF...HWRF...AND GFDL...SHOW A TURN BACK TOWARD THE NORTH NEAR THE END OF THE FORECAST PERIOD. THIS APPEARS TO BE IN RESPONSE TO A WEAK TROUGH THAT MOVES THROUGH THE SOUTHEASTERN UNITED STATES BEHIND THE HURRICANE. THE UPDATED TRACK FORECAST HAS BEEN SHIFTED EASTWARD AT 72 AND 96 HOURS BUT THE NEW 5-DAY POINT IS STILL ALONG THE LEFT SIDE OF THE GUIDANCE ENVELOPE...IN AGREEMENT WITH THE MODELS MENTIONED ABOVE. USERS ARE REMINDED THAT LARGE FORECAST ERRORS ARE POSSIBLE AT THE LONGER LEAD TIMES. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 20.9N 71.5W 80 KT 90 MPH 12H 24/0600Z 21.5N 72.7W 85 KT 100 MPH 24H 24/1800Z 22.7N 74.2W 95 KT 110 MPH 36H 25/0600Z 24.2N 75.5W 105 KT 120 MPH 48H 25/1800Z 26.1N 76.7W 110 KT 125 MPH 72H 26/1800Z 30.0N 77.2W 110 KT 125 MPH 96H 27/1800Z 34.0N 76.2W 100 KT 115 MPH 120H 28/1800Z 39.0N 74.8W 75 KT 85 MPH $$ FORECASTER BROWN