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Tropical Storm ISIS (Text)

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TROPICAL STORM ISIS DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 AM PDT MON SEP 13 2004
 
ENHANCED INFRARED ANIMATION DEPICTS THAT THE LOW-LEVEL CIRCULATION
CENTER REMAINS DISPLACED ABOUT 30 NM TO THE NORTHEAST OF WEAKENING
DEEP CONVECTION. LAST NIGHT'S QUIKSCAT AMBIGUITY ANALYSIS SUPPORTS
A POSITION SLIGHTLY FARTHER SOUTH THAN PREVIOUSLY THOUGHT. UW-CIMSS
ANALYSES INDICATES THAT 10 TO 20 KT OF EASTERLY SHEAR PERSISTS OVER
ISIS. CURRENT SATELLITE INTENSITY ESTIMATES REMAIN AT 45 KT...
ALTHOUGH DATA-T NUMBERS HAVE DECREASED TO 2.0 AND 2.5...30 AND 35
KT RESPECTIVELY. THE QUIKSCAT PASS ALSO REVEALED NUMEROUS 40 AND 45
KT FLAGGED BUT POSSIBLY VALID WIND VECTORS OVER THE SOUTHWEST
QUADRANT. WE WILL WAIT FOR VISIBLE IMAGERY AND THIS AFTERNOON'S
QUIKSCAT PASS BEFORE DECREASING THE INTENSITY. THE FORECAST
INTENSITY FOLLOWS CLOSER TO THE THE GFDL THAN THE SHIPS. AS
MENTIONED IN EARLIER DISCUSSIONS...SHIPS HAS INDICATED CONSIDERABLY
UNREALISTICALLY LOW SHEAR VALUES OVER THE PAST FEW DAYS.

INITIAL MOTION IS WESTWARD OR 270/9 KT.  GLOBAL MODELS AND THE GFDL
DEPICT A RIDGE TO THE NORTHWEST OF ISIS GRADUALLY WEAKENING AND
RETROGRADING WEST AFTER THE 48 HOUR PERIOD.  AFTERWARD...GUIDANCE
SUGGESTS ISIS SHOULD SLOW AND DRIFT OR STAIR-STEP WITHIN A
DEVELOPING WEAKNESS EXPECTED TO EXTEND SOUTHWEST FROM SOUTHERN
CALIFORNIA/BAJA. MODELS ARE ALSO SHOWING A PERIPHERAL RIDGE
BUILDING SLIGHTLY BETWEEN ISIS AND JAVIER...WHICH WOULD ALSO
SUPPORT A SLIGHT DRIFT NORTH LATE IN THE PERIOD. THE OFFICIAL
FORECAST IS SIMILAR TO THE PREVIOUS AND AGREES WITH THE CONU
CONSENSUS. 
 
FORECASTER ROBERTS/FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 17.3N 127.3W    45 KT
 12HR VT     14/0000Z 17.3N 128.5W    45 KT
 24HR VT     14/1200Z 17.3N 129.8W    50 KT
 36HR VT     15/0000Z 17.3N 130.8W    50 KT
 48HR VT     15/1200Z 17.4N 131.2W    50 KT
 72HR VT     16/1200Z 17.5N 131.5W    50 KT
 96HR VT     17/1200Z 17.5N 132.0W    50 KT
120HR VT     18/1200Z 18.0N 132.5W    50 KT
 
 
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