Tropical Depression FIFTEEN-E

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TROPICAL DEPRESSION FIFTEEN-E DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152007
800 AM PDT MON OCT 15 2007
 
EARLY MORNING VISIBLE SATELLITE IMAGERY INDICATES THAT THE
CENTER IS EXPOSED EAST OF THE LARGE AREA OF COLD CLOUDS TOPS...DUE
TO MODERATE EASTERLY SHEAR.  THIS POSITION IS SLIGHTLY SOUTHEAST OF
THE EARLIER ESTIMATES AND SUGGESTS THAT THE DEPRESSION MOVED VERY
LITTLE OVERNIGHT.  LIGHTNING DATA REVEAL THAT THE AREA OF ACTIVE
CONVECTION IS RATHER SMALL...WITH MOST OF THE COLD CLOUDS BEING
ASSOCIATED WITH CIRRUS OUTFLOW TO THE WEST.
 
DVORAK INTENSITY ESTIMATES FROM BOTH AGENCIES SUPPORT TROPICAL STORM
STRENGTH...BUT THE CENTER LOCATIONS OF THESE FIXES WERE CLOSER TO
THE DEEP CONVECTION.  SINCE THE VISIBLE IMAGERY SHOWS THE CENTER IS
FARTHER EAST...THE INITIAL INTENSITY WILL REMAIN 30 KT.  MOST OF
THE DYNAMICAL MODELS AND THE SHIPS GUIDANCE ARE LESS BULLISH IN
DECREASING THE EASTERLY SHEAR OVER THE CYCLONE.  IN FACT...THE
SHIPS GUIDANCE KEEPS THE SHEAR 15 KT OR GREATER THROUGHOUT MOST OF
THE FIVE-DAY FORECAST PERIOD.  THE NEW INTENSITY FORECAST IS
LOWERED SLIGHTLY FROM THE PREVIOUS ADVISORY AND IS IN CLOSE
AGREEMENT WITH THE ICON CONSENSUS.
 
THE INITIAL MOTION IS ESTIMATE IS 330/2.  THE DEPRESSION IS FORECAST
TO MOVE VERY LITTLE DURING THE NEXT 2-3 DAYS.  THE WEAK STEERING
CURRENTS RESULT FROM THE LACK OF A STRONG SUBTROPICAL RIDGE TO THE
NORTH OF THE TROPICAL CYCLONE...DUE TO A TROUGH APPROACHING THE
WEST COAST OF THE UNITED STATES.  AS MENTIONED IN THE PREVIOUS
DISCUSSION...IT WOULD NOT BE SURPRISING TO SEE SOME EASTWARD MOTION
OF THE DEPRESSION DURING THE NEXT COUPLE OF DAYS...AS IT COULD GET
PULLED EASTWARD BY A LARGE LOW- TO MID-LEVEL CYCLONIC GYRE NEAR
MEXICO.  LATER IN THE FORECAST PERIOD...AS THE TROUGH
MOVES EASTWARD...WEAK RIDGING IS FORECAST BUILD NORTH OF THE
CYCLONE....WHICH SHOULD INDUCE A SLOW NORTHWESTWARD MOTION.  THE
OFFICIAL FORECAST GENERALLY FOLLOWS THE GFDL...HWRF...AND GFS
SOLUTIONS.  HOWEVER...THERE IS A LARGE SPREAD IN THE FORWARD MOTION
OF THE CYCLONE IN THESE MODELS.  FOR NOW...THE OFFICIAL FORECAST IS
NEAR THE CONSENSUS OF THOSE MODELS...WHICH IS ALSO CLOSE TO THE
PREVIOUS NHC FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/1500Z 15.2N 108.9W    30 KT
 12HR VT     16/0000Z 15.3N 108.9W    35 KT
 24HR VT     16/1200Z 15.6N 108.9W    40 KT
 36HR VT     17/0000Z 15.9N 108.9W    45 KT
 48HR VT     17/1200Z 16.3N 109.0W    45 KT
 72HR VT     18/1200Z 16.9N 109.4W    45 KT
 96HR VT     19/1200Z 17.5N 110.0W    45 KT
120HR VT     20/1200Z 18.3N 111.0W    40 KT
 
$$
FORECASTER BROWN
 
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