[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 161629
TCDAT4
HURRICANE IRENE DISCUSSION NUMBER  48...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT TUE AUG 16 2005
...CORRECTED TO REPLACE WORD EXTRACURRICULAR WITH EXTRATROPICAL...
IRENE IS MAINTAINING INTENSITY AT THIS TIME...AS AN EYE HAS BEEN
EVIDENT ON BOTH VISIBLE AND INFRARED IMAGES.  SSM/I IMAGERY ALSO
SHOWS AN EYE...THAT IS CIRCULAR AND 20 N MI IN DIAMETER WITH A
CLOSED WALL...ALBEIT A LITTLE WEAK OVER THE SOUTHERN SEMICIRCLE.
DVORAK CLASSIFICATIONS GIVE A T-NUMBER OF 4.5 WHICH SUPPORTS A
CURRENT INTENSITY OF 75 KT.  EVEN THOUGH THE HURRICANE LOOKS QUITE
HEALTHY AT THE MOMENT...ONLY A SMALL NORTHWARD COMPONENT OF MOTION
WILL BRING THE SYSTEM INTO AN ENVIRONMENT OF MUCH HIGHER SHEAR...
GREATER THAN 30 KNOTS.  THE OFFICIAL INTENSITY FORECAST... LIKE THE
PREVIOUS ONE...SHOWS A WEAKENING TREND COMMENCING WITHIN 12-24
HOURS AND THEN WEAKENS IRENE AT A SLIGHTLY FASTER RATE THAN
PREDICTED BY THE SHIPS GUIDANCE.  GLOBAL MODELS INDICATE THAT IRENE
WILL BEGIN TO INTERACT WITH A BAROCLINIC ZONE IN ABOUT 36 HOURS.
AFTER EXTRATROPICAL TRANSITION...THE SYSTEM WILL LIKELY MERGE
WITH OR BECOME ABSORBED BY ANOTHER EXTRATROPICAL CYCLONE NEAR
SOUTHERN GREENLAND.

INITIAL MOTION IS ESTIMATED TO BE 080/9.  THE HURRICANE HAS MOVED ON
A MORE EASTERLY TRACK THAN ANTICIPATED...IN PART DUE TO A LACK OF
MID-LEVEL RIDGING TO ITS SOUTHEAST...RESULTING IN A MORE ZONAL
STEERING CURRENT THAN EXPECTED.  HOWEVER AS A 500 MB TROUGH MOVES
INTO THE CANADIAN MARITIME DURING THE NEXT DAY OR SO...A GRADUAL
TURN TO THE LEFT...AHEAD OF THIS TROUGH...IS ANTICIPATED.  THE
OFFICIAL TRACK FORECAST IS IN GOOD AGREEMENT WITH THE LATEST
GFS...WHICH APPEARS TO HAVE A GOOD INITIALIZATION OF THE TROPICAL
CYCLONE.

FORECASTER PASCH


FORECAST POSITIONS AND MAX WINDS

INITIAL      16/1500Z 36.7N  62.4W    75 KT
 12HR VT     17/0000Z 37.2N  60.9W    70 KT
 24HR VT     17/1200Z 38.3N  58.8W    65 KT
 36HR VT     18/0000Z 41.0N  54.5W    55 KT...BECOMING EXTRATROPICAL
 48HR VT     18/1200Z 46.0N  48.0W    50 KT...EXTRATROPICAL
 72HR VT     19/1200Z 55.0N  36.0W    45 KT...EXTRATROPICAL
 96HR VT     20/1200Z...ABSORBED


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