[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 071444
TCDAT4
TROPICAL STORM IRENE DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT SUN AUG 07 2005

THE DEPRESSION IS UPGRADED TO A TROPICAL STORM ON THE BASIS OF A
QUIKSCAT PASS AT 0849Z THIS MORNING...SHOWING 40 KT VECTORS JUST
OUTSIDE THE DEEP CONVECTION TO THE NORTH OF THE CENTER. THE
AMBIGUITY VECTORS FROM THIS PASS ALSO SHOW THE DYING CENTER THAT
WAS TRACKED WESTWARD LAST EVENING AND THE BEGINNINGS OF THE NEW
CENTER THAT FORMED FARTHER NORTH. THE STORM UPGRADE IS ALSO
SUPPORTED BY DVORAK CLASSIFICATIONS OF T2.5 FROM TAFB AND AFWA.
SINCE THE TIME OF THE QUIKSCAT PASS...THE DEEP CONVECTION NEAR THE
CENTER AS WELL AS THE ORGANIZATION HAS DIMINISHED SOMEWHAT...SO THE
INITIAL INTENSITY WILL BE SET AT 35 KT.

IT IS SOMETIMES MORE PRODUCTIVE TO TRACK THE OVERALL DISTURBANCE
THAN THE CIRCULATION CENTER ITSELF...IN THIS CASE IGNORING THE
CIRCULATIONS THAT HAVE FORMED...MOVED MORE WESTWARD...AND THEN
DIED...ONLY TO BE REPLACED BY NEW CENTERS TO THE NORTH.  DOING SO
YIELDS AN OVERALL SYSTEM MOTION OF 300/8.  A MID-LEVEL RIDGE
CURRENTLY LIES TO THE NORTHWEST OF IRENE. THE GFS...NOGAPS...
UKMET...AND ECMWF ALL AGREE THAT THIS RIDGE WILL MOVE WESTWARD AND
WEAKEN OVER THE NEXT 5 DAYS. IRENE IS EXPECTED TO CONTINUE A
GENERAL...IF ERRATIC...WEST-NORTHWESTWARD TRACK AND THEN TURN
NORTHWESTWARD INTO A WEAKNESS TO THE EAST OF THIS RIDGE. THE
OFFICIAL FORECAST IS BASED ON A BLEND OF THE GFS AND GFDL SOLUTIONS
AND IS ALSO VERY CLOSE TO THE FSU SUPERENSEMBLE.

IRENE IS ONLY SLOWLY MAKING ITS WAY TOWARD WARMER WATERS.  WATER
VAPOR IMAGERY AND GLOBAL MODEL GUIDANCE SUGGEST THAT AN UNFAVORABLE
UPPER FLOW PATTERN IS LIKELY TO PERSIST FOR ANOTHER COUPLE OF DAYS.
CONSEQUENTLY...LITTLE CHANGE IN STRENGTH IS EXPECTED IN THE SHORT
TERM.  THE GFDL NO LONGER MAKES IRENE A HURRICANE AND IN FACT SHOWS
LITTLE CHANGE OVER THE NEXT 5 DAYS.  THE OFFICIAL FORECAST...WHICH
FAVORS THE SHIPS GUIDANCE...ALLOWS FOR SOME STRENGTHENING NEAR THE
END OF THE FORECAST PERIOD IN RESPONSE TO WARMER WATERS AND THE
POSSIBILITY OF LESS SHEAR.

THE 2005 HURRICANE SEASON CONTINUES ON ITS RECORD-SETTING PACE.
IRENE IS THE EARLIEST NINTH NAMED STORM ON RECORD...BREAKING THE
OLD MARK BY 13 DAYS.  NORMALLY BY THIS DATE ONLY TWO NAMED STORMS
HAVE FORMED.

FORECASTER FRANKLIN


FORECAST POSITIONS AND MAX WINDS

INITIAL      07/1500Z 20.5N  45.5W    35 KT
 12HR VT     08/0000Z 20.9N  47.0W    35 KT
 24HR VT     08/1200Z 21.5N  49.0W    35 KT
 36HR VT     09/0000Z 22.1N  50.6W    35 KT
 48HR VT     09/1200Z 22.8N  52.1W    40 KT
 72HR VT     10/1200Z 24.5N  55.5W    45 KT
 96HR VT     11/1200Z 27.5N  58.0W    50 KT
120HR VT     12/1200Z 31.0N  59.5W    55 KT


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