Tropical Storm ISIS

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TROPICAL STORM ISIS DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 PM PDT THU SEP 09 2004
 
THE STORM CONTINUES IN ABOUT THE SAME STATE THAT IT WAS IN THE LAST
ADVISORY.  THE LOW-LEVEL CIRCULATION CENTER REMAINS ALMOST EXPOSED
ON THE NORTHEAST EDGE OF AN AREA OF POORLY-ORGANIZED DEEP
CONVECTION.  APPARENTLY THERE IS ENOUGH EAST-NORTHEASTERLY VERTICAL
SHEAR OVER THE SYSTEM TO PREVENT STRENGTHENING...BUT NOT ENOUGH
SHEAR TO WEAKEN IT.   A QUIKSCAT PASS FROM SEVERAL HOURS AGO
INDICATED THAT THE CURRENT INTENSITY REMAINS NEAR 40 KT...WHICH IS
IN GENERAL AGREEMENT WITH DVORAK CLASSIFICATIONS.  THE OFFICIAL
WIND SPEED FORECAST PRESUMES SOME  RELAXATION OF THE SHEAR OVER THE
NEXT DAY OR SO...ALLOWING FOR SLIGHT STRENGTHENING.  HOWEVER BY 48
HOURS OR SO...SEA SURFACE TEMPERATURES BECOME MARGINAL...WHICH
SHOULD PROHIBIT STRENGTHENING LATER IN THE PERIOD.
 
INITIAL MOTION IS WEST-NORTHWESTWARD AT ABOUT 8 KT.  THE EASTERLY
STEERING CURRENT SHOULD STRENGTHEN A BIT OVER THE NEXT FEW DAYS.
THEREFORE A TURN TO THE WEST WITH SOME INCREASE IN FORWARD SPEED IS
FORECAST.  HOWEVER THIS OFFICIAL FORECAST IS NOT QUITE AS FAST AS
THE ONES FROM THE PREVIOUS TWO ADVISORIES.
 
THE WIND RADII HAVE BEEN ADJUSTED USING THE QUIKSCAT DATA...WHICH
SHOW LITTLE EXTENT OF THE TROPICAL STORM FORCE WINDS OVER THE
NORTHWEST QUADRANT.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/2100Z 17.4N 113.8W    40 KT
 12HR VT     10/0600Z 17.8N 115.1W    45 KT
 24HR VT     10/1800Z 18.4N 117.6W    50 KT
 36HR VT     11/0600Z 18.8N 120.1W    50 KT
 48HR VT     11/1800Z 19.2N 122.9W    50 KT
 72HR VT     12/1800Z 19.5N 128.5W    50 KT
 96HR VT     13/1800Z 19.5N 133.5W    40 KT
120HR VT     14/1800Z 19.5N 139.0W    40 KT
 
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