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TROPICAL STORM HERNAN DISCUSSION NUMBER 3
NATIONAL WEATHER SERVICE MIAMI FL
2 PM PDT FRI AUG 30 2002
THINGS HAVE HOPEFULLY CLARIFIED SOMEWHAT THIS AFTERNOON...BOTH IN
TERMS OF THE INITIAL CONDITION AND THE FORECAST. HERNAN IS BECOMING
BETTER ORGANIZED...MORE CIRCULAR AND WITH GOOD BANDING FEATURES AND
A BETTER-DEFINED OUTFLOW. A QUIKSCAT PASS NEAR 12Z THIS MORNING
SUPPORTED WINDS OF 40 KT OR SO. DVORAK ESTIMATES FROM TAFB AND SAB
ARE 35 AND 45 KT...RESPECTIVELY...AND THE INITIAL INTENSITY IS
INCREASED TO 45 KT.
WITH VISIBLE IMAGERY AND THE IMPROVED ORGANIZATION...THE INITIAL
POSITION AND MOTION IS MORE CERTAIN. THE INITIAL MOTION IS
ESTIMATED TO BE 310/7. HERNAN WAS WELL INITIALIZED IN BOTH THE AVN
AND UKMET MODELS AT 12Z TODAY...AND PERHAPS AS A RESULT THE GUIDANCE
SUITE IS IN MUCH BETTER AGREEMENT THAN IT WAS EARLIER. HERNAN IS
EXPECTED TO MOVE GENERALLY WEST-NORTHWESTWARD AROUND THE PERIPHERY
OF A MID-LEVEL HIGH CENTERED OVER THE SOUTHWESTERN UNITED STATES.
THE OFFICIAL FORECAST IS NEAR THE CENTER OF A WELL-CLUSTERED
GUIDANCE ENVELOPE...AND CLOSEST TO THE GFDL.
WITH AN IMPROVED ORGANIZATION...OUTFLOW PATTERN...AND LESS
LIKELIHOOD OF A MORE NORTHERLY TRACK INTO A HIGHER SHEAR
ENVIRONMENT...THE INTENSITY FORECAST HAS BEEN BUMPED UP FROM THE
PREVIOUS ADVISORY. THE GFDL TAKES THE SYSTEM TO ABOUT 100
KT...WHILE THE SHIPS MODEL PEAKS OUT AT 81 KT.
WIND RADII HAVE BEEN ADJUSTED BASED ON THIS MORNINGS QUIKSCAT PASS.
FORECASTER FRANKLIN
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/2100Z 14.4N 104.3W 45 KTS
12HR VT 31/0600Z 14.9N 105.4W 55 KTS
24HR VT 31/1800Z 15.4N 107.0W 65 KTS
36HR VT 01/0600Z 16.0N 108.5W 75 KTS
48HR VT 01/1800Z 17.0N 110.0W 80 KTS
72HR VT 02/1800Z 18.5N 113.5W 85 KTS
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