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TROPICAL STORM HERNAN DISCUSSION NUMBER   2
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT FRI AUG 30 2002
 
DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB ARE 35 KT...AND THE 
DEPRESSION IS UPGRADED TO A TROPICAL STORM ON THIS BASIS.  HERNAN IS 
GENERATING AMPLE VERY COLD CONVECTION IN TWO MAIN CLUSTERS NORTHEAST 
AND WEST OF THE PRESUMED CENTER...ALTHOUGH BANDING IS NOT YET 
APPARENT.  THE SURFACE CIRCULATION STILL IS ELONGATED NE-SW.  THE 
OUTFLOW PATTERN SHOWS PLENTY OF DIVERGENCE BUT THERE IS NOT MUCH 
ANTICYCLONIC FLOW ALOFT.

THE INITIAL MOTION REMAINS UNCERTAIN BUT IS ESTIMATED TO BE 330/3.  
NEITHER THE AVN...UKMET...NOR THE NOGAPS APPEAR TO INITIALIZE HERNAN 
VERY WELL...SO I DO NOT HAVE A GREAT DEAL OF CONFIDENCE IN THEIR 
RESPECTIVE FORECASTS.  HOWEVER...ALL GUIDANCE SUGGESTS THAT HERNAN 
WILL TAKE A GENERALLY WEST-NORTHWESTERLY TRACK AROUND THE PERIPHERY 
OF A MID-LEVEL RIDGE CURRENTLY CENTERED OVER THE SOUTHWESTERN UNITED 
STATES.  ONLY THE UKMET INDICATES A CLOSE APPROACH OF THE CYCLONE TO 
THE MEXICAN COAST.  THE OFFICIAL FORECAST LEANS TOWARDS THE SOLUTION 
OFFERED BY THE BETA-ADVECTION MODELS.

THE SHEAR OVER THE CYCLONE IS CURRENTLY LOW AND THE WATER IS 
WARM...SO CONDITIONS ARE FAVORABLE FOR SOME INTENSIFICATION.  ONE 
INHIBITING FACTOR MAY BE AN UPPER TROUGH TO THE NORTH OF 
HERNAN...WHICH COULD BECOME SIGNIFICANT IF HERNAN TAKES A MORE 
NORTHERLY TRACK THAN ANTICIPATED.  THE OFFICIAL FORECAST ASSUMES 
THAT THIS FEATURE WILL HAVE ONLY A MODEST EFFECT ON THE 
INTENSIFICATION...AND IS ROUGHLY A COMPROMISE BETWEEN THE SHIPS AND 
GFDL GUIDANCE.
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     30/1500Z 13.9N 103.2W    35 KTS
12HR VT     31/0000Z 14.2N 103.5W    45 KTS
24HR VT     31/1200Z 14.8N 104.5W    55 KTS
36HR VT     01/0000Z 15.5N 105.7W    60 KTS
48HR VT     01/1200Z 16.0N 107.0W    65 KTS
72HR VT     02/1200Z 17.0N 110.5W    75 KTS
 
 
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