[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 240259
TCDAT4

HURRICANE IRENE DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092011
1100 PM EDT TUE AUG 23 2011

IT IS FORTUNATE THAT WE HAVE A NOAA HIGH ALTITUDE JET SAMPLING THE
ENVIRONMENT OF IRENE AND TWO HURRICANE HUNTER AIRCRAFT...ONE FROM
NOAA AND THE OTHER FROM THE AIR FORCE...IN THE EYE OF THE HURRICANE
TONIGHT. THE SATELLITE PRESENTATION HAS IMPROVED WITH A RAGGED EYE
EMBEDDED IN DEEP CONVECTION AND A WELL ESTABLISHED OUTFLOW.  THIS
HAS RESULTED IN THE INCREASE OF BOTH OBJECTIVE AND SUBJECTIVE
T-NUMBERS. THE CENTRAL PRESSURE REPORTED FROM BOTH PLANES HAS COME
DOWN TO 969 MB AND THE MAX FLIGHT-LEVEL WIND MEASURED WAS 101
KNOTS. HOWEVER...DATA FROM THE SFMR INDICATE THAT THE SURFACE WINDS
HAVE NOT INCREASED YET AND THE INITIAL INTENSITY REMAINS AT 80
KNOTS.  IRENE WILL BE TRAVERSING VERY WARM WATERS AND ALTHOUGH THE
UPPER-LEVEL WINDS ARE NOT IDEAL FOR RAPID INTENSIFICATION...THE
OVERALL CONDITIONS FAVOR STRENGTHENING DURING THE NEXT DAY OR TWO
AS INDICATED IN THE PREVIOUS FORECAST...AND IRENE IS EXPECTED TO BE
A MAJOR HURRICANE AS IT MOVES OVER THE CENTRAL BAHAMAS IN ABOUT A
DAY.

SATELLITE AND RECONNAISSANCE FIXES INDICATE THAT IRENE IS STILL
MOVING TOWARD THE WEST-NORTHWEST AT A SLOW PACE OF 8 KNOTS. SINCE
THERE HAS BEEN NO CHANGE IN THE EXPECTED EVOLUTION OF THE STEERING
PATTERN...THERE IS NO REASON TO MODIFY THE PREVIOUS OFFICIAL
FORECAST WHICH BRINGS THE HURRICANE NORTHWESTWARD ACROSS THE
BAHAMAS...AND THEN NORTHWARD PARALLELING THE UNITED STATES
SOUTHEAST COAST AND VERY CLOSE TO OR OVER THE OUTER BANKS. IRENE
SHOULD CONTINUE NORTHWARD OR NORTH-NORTHEASTWARD ALONG THE MID
ATLANTIC COAST. THE TRACK GUIDANCE IS IN BETTER AGREEMENT TONIGHT
AND EVEN THE STUBBORN GFDL WHICH PREVIOUSLY INSISTED ON BRINGING
IRENE TOWARD FLORIDA HAS NOW SHIFTED EASTWARD AND HAS JOINED THE
OTHER DYNAMICAL MODELS. THIS INCREASES THE CONFIDENCE IN THE TRACK
FORECAST EVEN MORE.

USERS ARE REMINDED THAT LARGE FORECAST ERRORS ARE POSSIBLE AT THE
LONGER LEAD TIMES.


FORECAST POSITIONS AND MAX WINDS

INIT  24/0300Z 21.3N  72.4W   80 KT  90 MPH
 12H  24/1200Z 22.0N  73.5W   85 KT 100 MPH
 24H  25/0000Z 23.5N  75.0W   95 KT 110 MPH
 36H  25/1200Z 25.5N  76.5W  105 KT 120 MPH
 48H  26/0000Z 27.5N  77.0W  110 KT 125 MPH
 72H  27/0000Z 31.0N  77.0W  110 KT 125 MPH
 96H  28/0000Z 36.0N  76.0W  100 KT 115 MPH
120H  29/0000Z 40.5N  73.5W   75 KT  85 MPH

$$
FORECASTER AVILA


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