417 
 WTPZ42 KNHC 200258
 TCDEP2
 TROPICAL DEPRESSION SEVEN-E DISCUSSION NUMBER   4
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 8 PM PDT THU AUG 19 2004
  
 THERE HAS BEEN SOME INCREASE IN DEEP CONVECTION NEAR THE CENTER OF
 TROPICAL DEPRESSION SEVEN-E DURING THE EVENING...WITH THE COLDEST
 TOPS CURRENTLY JUST NORTHEAST OF THE CENTER.  THE SYSTEM IS NEARING
 TROPICAL STORM STRENGTH...AS SATELLITE INTENSITY ESTIMATES ARE 35
 KT FROM AFWA AND SAB...AND 30 KT FROM TAFB.  GIVEN THE SOMEWHAT
 RAGGED OVERALL APPEARANCE AT THIS TIME...IT WILL REMAIN A 30 KT
 DEPRESSION.
 
 THE 12 HR INITIAL MOTION IS 300/13...AND THE SHORT-TERM MOTION MAY
 BE A LITTLE MORE TO THE RIGHT.  THE CYCLONE IS ON THE SOUTH SIDE OF
 THE SUBTROPICAL RIDGE WHICH IS FORECAST TO WEAKEN FOR 24-48 HR
 FOLLOWED BY SLOW STRENGTHENING.  THIS SHOULD ALLOW A GENERAL
 WEST-NORTHWESTERLY MOTION FOR 48 HR OR SO...FOLLOWED BY A GRADUAL
 WESTWARD TURN.  TRACK GUIDANCE GENERALLY AGREES WITH THIS
 SCENARIO...WITH A FAIRLY NORMAL SPREAD LATER IN THE FORECAST
 PERIOD.  THE GFDL AND UKMET CALL FOR A WESTWARD MOTION AFTER 72
 HR...THE BAMD GOES NORTHWEST...AND THE NOGAPS AND GFS TURN
 SOUTHWESTWARD.  THE OFFICIAL FORECAST CALLS FOR A WESTWARD TURN IN
 BEST AGREEMENT WITH GUNS AND GUNA...AND IT IS SHIFTED ABOUT A
 DEGREE TO THE NORTH OF THE PREVIOUS TRACK AFTER 48 HR.
 
 THE DEPRESSION IS CURRENTLY OVER 28C SEA SURFACE TEMPERATURES...BUT
 THE FORECAST TRACK CARRIES IT OVER 25-26C SSTS AFTER 24 HR.  IF
 THIS HAPPENS IT SHOULD LIMIT INTENSIFICATION AS SHOWN BY THE SHIPS
 MODEL...AND THE INTENSITY FORECAST CLOSELY FOLLOWS THAT MODEL.  IT
 IS NOT IMPOSSIBLE THAT THE CYCLONE COULD BECOME A HURRICANE AS
 FORECAST BY THE GFDL...ALTHOUGH THAT IS MOST LIKELY IF IT STAYS
 SOUTH OF THE CURRENT FORECAST TRACK.  THERE IS UNCERTAINTY ABOUT
 POTENTIAL VERTICAL SHEAR.  SATELLITE IMAGERY CURRENTLY INDICATES A
 SIGNIFICANT UPPER-LEVEL TROUGH ALONG 150W WHICH COULD CAUSE SHEAR
 IF IT REMAINS IN PLACE.  HOWEVER...THE GFS AND NOGAPS SUGGEST THE
 TROUGH WILL WEAKEN AND MOVE WESTWARD...WHICH COULD ALLOW FOR SOME
 STRENGTHENING WHEN THE CYCLONE FINDS GRADUALLY INCREASING SSTS
 AFTER 72 HR. 
  
 FORECASTER BEVEN
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      20/0300Z 13.2N 135.5W    30 KT
  12HR VT     20/1200Z 14.1N 137.1W    35 KT
  24HR VT     21/0000Z 15.1N 139.1W    40 KT
  36HR VT     21/1200Z 15.9N 140.9W    45 KT
  48HR VT     22/0000Z 16.6N 142.7W    50 KT
  72HR VT     23/0000Z 17.5N 146.0W    50 KT
  96HR VT     24/0000Z 17.5N 149.5W    50 KT
 120HR VT     25/0000Z 17.5N 154.0W    50 KT
  
  
 $$