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Hurricane IRENE (Text)

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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
 
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