[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 150850
TCDAT4
HURRICANE IRENE DISCUSSION NUMBER  43
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT MON AUG 15 2005

IRENE REMAINS BENEATH A LARGE UPPER-LEVEL ANTICYCLONE THAT OCCUPIES
MOST THE WESTERN ATLANTIC... AND THE HURRICANE IS TAKING ADVANTAGE
OF THIS ENVIRONMENT BY SUSTAINING SOME VERY DEEP CONVECTION THAT
HAS BECOME INCREASINGLY SYMMETRIC ABOUT THE CIRCULATION CENTER.
SUBJECTIVE DVORAK INTENSITY ESTIMATES ARE 65 KT FROM TAFB AND 77 KT
FROM SAB... AND A 3-HR AVERAGE ODT ESTIMATE ALSO YIELDS 77 KT.
BASED ON THE IMPROVED SATELLITE APPEARANCE COMPARED TO A FEW HOURS
AGO... THE ADVISORY INTENSITY IS INCREASED TO 75 KT. THE
UPPER-LEVEL OUTFLOW REMAINS WELL-ESTABLISHED... ASIDE FROM SOME
RESTRICTION TO THE NORTHWEST SINCE THE HURRICANE IS APPROACHING THE
MIDLATITUDE WESTERLIES ON THE NORTHERN SIDE OF THE UPPER-LEVEL
ANTICYCLONE. THESE WESTERLIES WILL SOON BE IMPARTING SHEAR ON THE
HURRICANE... SO THE WINDOW OF OPPORTUNITY FOR ANY FURTHER
STRENGTHENING SHOULD CLOSE IN ABOUT 12 HOURS... AND THIS SHOULD BE
FOLLOWED BY A WEAKENING TREND. THE NEW OFFICIAL INTENSITY FORECAST
PEAKS AT 80 KT IN 12 HOURS... SIMILAR TO THE SHIPS AND GFDL... THEN
FOLLOWS THE SHIPS WEAKENING TREND... EVEN THOUGH THE GFDL INSISTS
ON FURTHER STRENGTHENING TO NEAR 90 KT BEFORE IRENE REACHES COOLER
WATERS.

IRENE CONTINUES TO ROUND THE MID-LEVEL SUBTROPICAL RIDGE CENTERED
NEAR BERMUDA... AND THE INITIAL MOTION ESTIMATE IS NOW 035/10. THIS
RIDGE IS FORECAST BY THE GLOBAL MODELS TO FLATTEN OUT AS IRENE
MOVES TO ITS NORTH DURING THE NEXT 24 HOURS... RESULTING IN MORE
ZONAL WESTERLY FLOW THAT SHOULD TURN IRENE MORE TO THE
EAST-NORTHEAST DURING THE NEXT COUPLE OF DAYS... GRADUALLY
ACCELERATING AWAY FROM THE U.S. EAST COAST. THE GFS REMAINS THE
FAST OUTLIER... BUT THE OFFICIAL FORECAST WILL REMAIN CLOSER TO THE
DYNAMICAL MODEL CONSENSUS AND THE PREVIOUS ADVISORY. ALONG THE
OFFICIAL FORECAST TRACK... IRENE WOULD PASS OVER THE NORTH WALL OF
THE GULF STREAM IN ABOUT 48 HOURS... AND IT SHOULD CONTINUE TO
WEAKEN THEREAFTER AS AN EXTRATROPICAL SYSTEM OVER COOLER WATERS.

FORECASTER KNABB


FORECAST POSITIONS AND MAX WINDS

INITIAL      15/0900Z 36.1N  68.3W    75 KT
 12HR VT     15/1800Z 37.0N  66.5W    80 KT
 24HR VT     16/0600Z 38.1N  63.8W    75 KT
 36HR VT     16/1800Z 39.3N  60.7W    65 KT
 48HR VT     17/0600Z 41.3N  57.3W    60 KT
 72HR VT     18/0600Z 47.5N  48.0W    50 KT...EXTRATROPICAL
 96HR VT     19/0600Z 56.0N  39.0W    40 KT...EXTRATROPICAL
120HR VT     20/0600Z...ABSORBED


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