[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 110232
TCDAT4
TROPICAL STORM IRENE DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT WED AUG 10 2005

IRENE'S CLOUD PATTERN HAS BECOME SLIGHTLY BETTER ORGANIZED THIS
EVENING.  A CONVECTIVE BAND OVER THE EASTERN PORTION OF THE SYSTEM
WRAPS NEARLY HALFWAY AROUND THE CIRCULATION.  DVORAK INTENSITY
ESTIMATES ARE A CONSENSUS 35 KT FROM TAFB...SAB...AND AFWA.  THIS
SUPPORTS RE-UPGRADING THE CYCLONE TO TROPICAL STORM STATUS.  THE
UPPER-TROPOSPHERIC OUTFLOW IS BECOMING BETTER DEFINED EXCEPT TO THE
SOUTH WHERE IT IS BEING IMPEDED BY AN UPPER-LEVEL CYCLONE TO THE
SOUTHWEST OF THE STORM.  WATER VAPOR IMAGERY AND ANALYSES FROM THE
UNIVERSITY OF WISCONSIN CIMSS SHOW THAT THE NORTHERLY MID- TO
UPPER-LEVEL FLOW THAT HAD BEEN DISRUPTING THE TROPICAL CYCLONE IS
ABATING AND THAT IRENE IS MOVING INTO AN AREA OF DECREASING
VERTICAL SHEAR.  STRENGTHENING IS FORECAST...AS IN THE PREVIOUS
ADVISORY.  AS USUAL...THE FORECAST WIND SPEEDS IN THE 3 TO 5 DAY
TIME FRAME HAVE CONSIDERABLE UNCERTAINTY OWING TO A LACK OF SKILL
IN LONGER-RANGE TROPICAL CYCLONE INTENSITY PREDICTION.

RECENT CENTER FIXES FROM BOTH GEOSTATIONARY AND MICROWAVE IMAGERY
ARE SOMEWHAT TO THE NORTH OF THE PREVIOUS TRACK.  HOWEVER...FOR
CONTINUITY'S SAKE...I HAVE ADJUSTED THE CURRENT MOTION ONLY
SLIGHTLY TO THE RIGHT...290/11.  THE MAIN STEERING FEATURE THAT
CONCERNS US IS A MID-TROPOSPHERIC RIDGE THAT THE GLOBAL MODELS ARE
FORECASTING TO BUILD NEAR AND JUST EAST OF THE U.S. MID-ATLANTIC
STATES IN 3 TO 5 DAYS.  IT IS TOO EARLY TO DETERMINE WHETHER THIS
RIDGE WILL DRIVE IRENE TO THE SOUTHEAST U.S. COAST.  IT IS STILL
POSSIBLE THAT THE TROPICAL CYCLONE WILL BE ABLE TO MOVE MORE
NORTHWARD INTO A WEAKNESS IN THE RIDGE...AS SUGGESTED BY SOME OF
THE TRACK GUIDANCE SUCH AS THE U.K. MET. OFFICE GLOBAL MODEL AND
THE LATEST GFDL RUN...OR MOVE MORE WESTWARD AND REACH THE COAST AS
SHOWN BY THE ECMWF AND GFDN.  THE OFFICIAL FORECAST TRACK HAS BEEN
SHIFTED A LITTLE TO THE RIGHT OF THE PREVIOUS ONE...BUT IS STILL
WELL TO THE LEFT OF THE DYNAMICAL MODEL CONSENSUS.  THE NHC
FORECAST TRACK IS ALSO VERY SIMILAR TO THE LATEST FSU SUPERENSEMBLE
TRACK.

FORECASTER PASCH


FORECAST POSITIONS AND MAX WINDS

INITIAL      11/0300Z 23.5N  59.8W    35 KT
 12HR VT     11/1200Z 24.2N  61.5W    40 KT
 24HR VT     12/0000Z 25.4N  63.8W    45 KT
 36HR VT     12/1200Z 26.3N  65.7W    50 KT
 48HR VT     13/0000Z 27.2N  67.5W    55 KT
 72HR VT     14/0000Z 28.5N  70.0W    60 KT
 96HR VT     15/0000Z 30.5N  72.5W    65 KT
120HR VT     16/0000Z 32.5N  75.0W    70 KT


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