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TROPICAL STORM HERNAN DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT FRI AUG 30 2002

HERNAN HAS CONTINUED TO WRAP UP THIS EVENING...WITH A BAND OF
COLD CONVECTIVE TOPS NOW ENCIRCLING THE WELL-DEFINED CENTER.
SATELLITE INTENSITY ESTIMATES FROM TAFB...SAB...AND AFWA WERE ALL
55 KT AT 00Z...AND FURTHER DEVELOPMENT HAS OCCURRED SINCE THEN.
THE MAXIMUM WINDS ARE RAISED TO 60 KT FOR THIS ADVISORY. 

THE INITIAL MOTION IS 300/9.  MID-LEVEL RIDGING OVER THE
SOUTHWESTERN U.S. SHOULD STEER HERNAN WEST-NORTHWESTWARD FOR
AT LEAST 48 HR...AS INDICATED BY THE WELL-CLUSTERED LARGE-SCALE
MODELS AND NHC TRACK GUIDANCE.  BEYOND THAT TIME...THE RIDGE MAY
WEAKEN AS A LARGE DEEP LAYER TROUGH DEVELOPS OFF THE U.S. WEST
COAST.  WHILE NONE OF THE GUIDANCE SHOWS A NORTHWARD MOTION IN
RESPONSE TO THE TROUGH AT THIS TIME...IT WILL BE INTERESTING
TO SEE IF LATER MODEL RUNS TRY TO TURN HERNAN MORE TO THE RIGHT
LATER IN THE FORECAST PERIOD.
 
HERNAN IS OVER WARM WATER AND IN A LIGHT SHEAR ENVIRONMENT...AND
BOTH OF THESE ARE LIKELY TO CONTINUE FOR AT LEAST 36 HR.  THE 
INTENSITY FORECAST CALLS FOR FURTHER STRENGTHENING...AND THE 
STORM MAY BE STRONGER THAN THE CURRENTLY FORECAST 90 KT IN 36-48 HR.
AFTER THAT TIME...THE SEA SURFACE TEMPERATURES BEGIN TO GRADUALLY
COOL...SO INTENSIFICATION SHOULD CEASE.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     31/0300Z 14.9N 105.4W    60 KTS
12HR VT     31/1200Z 15.4N 106.5W    70 KTS
24HR VT     01/0000Z 16.1N 108.1W    80 KTS
36HR VT     01/1200Z 16.8N 109.6W    90 KTS
48HR VT     02/0000Z 17.5N 111.3W    90 KTS
72HR VT     03/0000Z 18.5N 114.0W    90 KTS
 
 
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