ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE IRENE DISCUSSION NUMBER 22 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011 500 PM EDT THU AUG 25 2011 THE EYE OF IRENE MOVED OVER ABACO ISLAND EARLIER THIS AFTERNOON. AN AUTOMATED WEATHER STATION ON THE ISLAND MEASURED A MINIMUM PRESSURE OF 950.4 MB AROUND 1700 UTC. THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING IRENE THIS AFTERNOON HAS REPORTED A 700 MB PEAK-FLIGHT WIND OF 99 KT. ALTHOUGH RECENT AIRCRAFT DATA DO NOT QUITE SUPPORT THE 100-KT ADVISORY INTENSITY...WE WILL HOLD THE INTENSITY FOR A LITTLE LONGER TO SEE IF THE AIRCRAFT FINDS HIGHER WINDS. IRENE CONTINUES MOVING NORTH-NORTHWESTWARD AT ABOUT 12 KT. THERE HAS BEEN NO CHANGE TO THE TRACK FORECAST REASONING. IRENE IS FORECAST TO TURN NORTHWARD BY EARLY FRIDAY AS IT MOVES THROUGH A BREAK IN THE SUBTROPICAL RIDGE. AFTER 24 HOURS...THE HURRICANE IS EXPECTED TO MOVE ON A HEADING BETWEEN NORTH AND NORTH-NORTHEAST AS A TROUGH BYPASSES THE CYCLONE TO THE NORTH. THIS WILL LEAVE THE IRENE IN A STEERING PATTERN THAT SHOULD KEEP THE HURRICANE ON THAT GENERAL HEADING AS IT MOVES VERY NEAR OR OVER MID-ATLANTIC COAST. THE TRACK GUIDANCE HAS COME INTO BETTER AGREEMENT ON THIS SOLUTION...AND THE CONFIDENCE IN THE TRACK FORECAST IS INCREASING. THE NEW TRACK HAS BEEN NUDGED WESTWARD AND IS CLOSE TO THE CENTER OF THE GUIDANCE ENVELOPE. IT IS ALSO IN GOOD AGREEMENT WITH THE 1200 UTC GFS. SINCE IRENE IS A LARGE TROPICAL CYCLONE...ONE SHOULD NOT FOCUS ON THE EXACT TRACK OF IRENE...AS SIGNIFICANT IMPACTS WILL BE FELT WELL AWAY FROM THE CENTER. THERE IS STILL SOME TIME FOR IRENE TO STRENGTHEN AS IT WILL BE MOVING OVER WARM WATER AND THE SHEAR REMAINS LOW. HOWEVER...THE UPDATED FORECAST CALLS FOR A LITTLE LOWER INTENSITY OVER THE FIRST 24-36 HOURS. IN ABOUT 48 HOURS...SOUTHWESTERLY SHEAR IS FORECAST TO INCREASE...WHICH SHOULD START A WEAKENING PROCESS. HOWEVER...SINCE IRENE HAS SUCH A LARGE AND INTENSE CIRCULATION... IT WILL PROBABLY BE SLOW TO WEAKEN. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 27.0N 77.3W 100 KT 115 MPH 12H 26/0600Z 28.7N 77.8W 100 KT 115 MPH 24H 26/1800Z 30.6N 77.8W 105 KT 120 MPH 36H 27/0600Z 32.5N 77.4W 100 KT 115 MPH 48H 27/1800Z 34.5N 76.9W 95 KT 110 MPH 72H 28/1800Z 39.8N 74.6W 75 KT 85 MPH...INLAND 96H 29/1800Z 48.5N 68.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 30/1800Z 56.0N 54.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ FORECASTER BROWN NNNN
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