Tropical Depression SEVEN-E

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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
 
 
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