Hurricane IRENE

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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
 
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