075 
 WTPZ42 KNHC 152035
 TCDEP2
 TROPICAL STORM ISIS DISCUSSION NUMBER  31
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 2 PM PDT WED SEP 15 2004
  
 THE EYE STRUCTURE SEEN EARLIER HAS COLLAPSED COMPLETELY DURING THE
 AFTERNOON...WITH DEEP CONVECTION NOW CONFINED TO A RELATIVELY SMALL
 AREA IN THE NORTHEASTERN SEMICIRCLE.  SATELLITE INTENSITY ESTIMATES
 ARE 65 KT FROM TAFB AND SAB...AND 55 KT FROM AFWA.  IN VIEW OF THE
 DEGENERATION...THE INITIAL INTENSITY IS DECREASED TO 60 KT...AND
 THIS MAY BE GENEROUS.
 
 THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 310/4.  ISIS IS EMBEDDED
 IN WEAK STEERING CURRENTS AND WILL GO NOWHERE FAST DURING THE NEXT
 FIVE DAYS.  MOST DYNAMICAL GUIDANCE CALLS FOR A SLOW WESTWARD TO
 WEST-NORTHWESTWARD DRIFT...AND THE OFFICIAL FORECAST TRACK WILL
 FOLLOW THAT SCENARIO.
  
 THE MORE NORTHERLY POSITION HAS PROBABLY BROUGHT ISIS OVER COOLER
 WATER...AND THIS IS LIKELY PLAYING A ROLE IN THE CURRENT WEAKENING. 
 BETWEEN THE COOL WATER AND STRATOCUMULUS ENTRAINMENT CURRENLY SEEN
 IN VISIBLE IMAGERY...ISIS SHOULD SLOWLY WEAKEN THROUGH THE FORECAST
 PERIOD.
  
 FORECASTER BEVEN
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      15/2100Z 18.2N 132.1W    60 KT
  12HR VT     16/0600Z 18.3N 132.4W    55 KT
  24HR VT     16/1800Z 18.4N 132.7W    55 KT
  36HR VT     17/0600Z 18.5N 133.0W    50 KT
  48HR VT     17/1800Z 18.5N 133.5W    45 KT
  72HR VT     18/1800Z 18.5N 134.0W    40 KT
  96HR VT     19/1800Z 18.5N 134.5W    35 KT
 120HR VT     20/1800Z 18.5N 135.0W    30 KT
  
  
 $$