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Tropical Storm ISIS


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TROPICAL STORM ISIS DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 AM PDT FRI SEP 10 2004
 
THERE HAS BEEN A MARKED DECREASE IN DEEP CONVECTION WITH ISIS THIS
MORNING.  I AM A LITTLE PUZZLED AS TO WHY...SINCE THE SSTS ARE
STILL AROUND 27C AND THE SHEAR DOES NOT APPEAR TO HAVE INCREASED
ANY.  DVORAK T NUMBERS ARE BEGINNING TO DECREASE...BUT THE MOST
RECENT QUIKSCAT PASS SUGGESTS THAT WINDS ARE STILL AROUND 40 KT. 
GLOBAL MODELS CONTINUE TO FORECAST A LESSENING OF THE SHEAR...BUT
THIS IS CLEARLY NOT HAPPENING AS QUICKLY AS EXPECTED.  THE OFFICIAL
FORECAST INTENSITY IS LOWERED ONLY A BIT FROM THE PREVIOUS ADVISORY
IN DEFERENCE TO BOTH THE SHIPS AND GFDL GUIDANCE...WHICH CONTINUE
TO SHOW STRENGTHENING...BUT IF THE SHEAR DOES NOT LESSEN VERY SOON
A WEAKENING TREND WILL COMMENCE MORE QUICKLY THAN INDICATED BELOW.

A NICE MICROWAVE PASS AT 08Z HELPS ESTABLISH THE INITIAL MOTION
ESTIMATE AT 270/8.  ISIS IS SOUTH OF A DEEP-LAYER RIDGE THAT IS
FORECAST TO PERSIST THROUGH THE FORECAST PERIOD.  MODEL GUIDANCE IS
TIGHTLY CLUSTERED ON A WESTERLY TRACK WITH A GRADUAL INCREASE IN
FORWARD SPEED.  THE OFFICIAL FORECAST ESSENTIALLY JUST UPDATES THE
PREVIOUS TRACK.
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 17.3N 116.2W    40 KT
 12HR VT     11/0000Z 17.5N 117.7W    40 KT
 24HR VT     11/1200Z 18.0N 120.0W    45 KT
 36HR VT     12/0000Z 18.6N 122.6W    45 KT
 48HR VT     12/1200Z 19.0N 125.5W    45 KT
 72HR VT     13/1200Z 19.0N 131.0W    45 KT
 96HR VT     14/1200Z 19.0N 137.0W    40 KT
120HR VT     15/1200Z 19.0N 144.0W    40 KT
 
 
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