ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE IRENE DISCUSSION NUMBER 30 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011 500 PM EDT SAT AUG 27 2011 THE CENTER OF IRENE HAS BEEN MOVING ACROSS EASTERN NORTH CAROLINA THIS AFTERNOON...AND THE RADAR PRESENTATION OF THE INNER CORE ACTUALLY IMPROVED FOR A FEW HOURS. SINCE THAT TIME...THE RAGGED EYE HAS FILLED IN BUT THE CENTER REMAINS WELL DEFINED ON RADAR...WHICH WARRANTS A RETURN TO TWO-HOURLY INTERMEDIATE ADVISORIES. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REPORTED PEAK FLIGHT-LEVEL WINDS OF 85-90 KT TO THE EAST OF THE CENTER DURING THE PAST FEW HOURS...AND A VERY RECENT CENTER DROP MEASURED A MINIMUM PRESSURE OF 950 MB. THERE HAVE NOT BEEN ANY RECENT SFMR DATA...BUT BASED ON THE EARLIER SHARP DISCREPANCY BETWEEN THE FLIGHT-LEVEL AND SURFACE WINDS...THE INITIAL INTENSITY IS REDUCED TO 70 KT. A SLOW WEAKENING IS EXPECTED AS IRENE MOVES ALONG THE COAST OF THE MID-ATLANTIC STATES DUE TO LAND INTERACTION...COLDER WATERS...DRY AIR ENTRAINMENT...AND INCREASING SOUTHWESTERLY SHEAR. BECAUSE THE LARGE WIND FIELD WILL TAKE TIME TO SPIN DOWN...HOWEVER...IRENE IS STILL EXPECTED TO REACH THE NEW YORK AREA AT OR NEAR HURRICANE STRENGTH. MORE SO THAN WITH MOST STORMS...THE WINDS WITH IRENE INCREASE SHARPLY WITH HEIGHT ABOVE THE SURFACE. AS IRENE MOVES THROUGH AREAS WITH HIGH-RISE STRUCTURES...THESE STRUCTURES WILL EXPERIENCE WINDS SIGNIFICANTLY STRONGER THAN INDICATED BY THE ADVISORY INTENSITY. WINDS AT THE 30-STORY LEVEL WILL LIKELY BE 20 PERCENT HIGHER THAN AT THE SURFACE...AND WINDS 80-100 STORIES UP COULD BE ABOUT 30 PERCENT HIGHER THAN AT THE SURFACE. THE CENTER CONTINUED NORTHWARD FOR A SHORT PERIOD OF TIME AFTER THE RELEASE OF THE PREVIOUS ADVISORY BUT HAS RESUMED A NORTHEASTWARD MOTION OF ABOUT 015/11. IRENE IS FORECAST TO MOVE NORTH- NORTHEASTWARD ALONG THE MID-ATLANTIC COAST TONIGHT AND OVER NEW ENGLAND ON SUNDAY. AFTER THE CYCLONE BECOMES EXTRATROPICAL IN 36-48 HOURS IT SHOULD TURN NORTHEASTWARD THEN EAST-NORTHEASTWARD IN THE MID-LATITUDE WESTERLIES. THE NEW TRACK FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY. NOTE THAT ESTIMATES OF STORM TOTAL RAINFALL HAVE BEEN INCREASED WITH THIS ADVISORY...TO 20 INCHES. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 36.2N 76.0W 70 KT 80 MPH 12H 28/0600Z 38.1N 75.1W 65 KT 75 MPH 24H 28/1800Z 41.7N 73.2W 60 KT 70 MPH...INLAND 36H 29/0600Z 46.2N 70.2W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 29/1800Z 50.7N 66.3W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 30/1800Z 56.5N 53.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 31/1800Z 59.0N 37.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 01/1800Z 61.0N 26.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ FORECASTER BROWN/FRANKLIN NNNN
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