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HURRICANE ISAAC DISCUSSION NUMBER  36
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT SAT SEP 30 2000
 
THOUGH VERY COLD CLOUDS PERSIST IN A PARTIAL RING...IR IMAGERY
SUGGESTS THE CIRCULATION IS BECOMING INCREASINGLY TILTED TOWARD THE
NORTHEAST.  THE SURFACE CENTER COULD BE 30 NM OR MORE SW OF THE
DEEPEST CONVECTION.  FOR THIS ADVISORY...AN INTERMEDIATE POSITION IS
CHOSEN AND THIS IMPLIES A LITTLE SLOWER MOTION...035/17 KT...THAN IN
THE PREVIOUS ADVISORY.  A GRADUAL DETERIORATION OF THE CLOUD PATTERN
CONTINUES AS ISAAC DECLINES AND THE ESTIMATED MAXIMUM WINDS ARE NOW
NEAR 80 KT.
 
WHILE SOME READJUSTMENT OF THE CENTER POSITION IS LIKELY LATER THIS
MORNING WHEN VISIBLE PICTURES APPEAR...THE FUTURE TRACK...IRONICALLY
...SEEMS MORE CERTAIN.  ISAAC IS EXPECTED TO BECOME FULLY ENTRAINED
IN THE WESTERLIES AND MOVE TOWARD THE NE...AS SHOWN BY THE GUIDANCE
AND PREVIOUS NHC FORECASTS.
 
THE TRANSITION PROCESS TO EXTRATROPICAL...OR POST-TROPICAL...FOR
ISAACS INTENSITY IS HANDLED QUITE DIFFERENTLY BY THE MODELS. THE
GFDL OUTPUT SHOWS...DISSIPATION...IN THREE TO FOUR DAYS...BUT IT
ALSO INDICATES 50-60 KT WINDS IN AN EXTRATROPICAL HYBRID.  THE
UKMET MODEL INDICATES AN INTENSE STORM THEN.  THE AVN HAS 45 KT
WINDS AT 850 MB ALONG THE FRONT FORECAST TO DEVELOP FROM ISAAC.  THE
OFFICIAL FORECAST SHOWS WEAKENING TO 50 KT...WITH THE EXTRATROPICAL
STAGE REACHED IN ABOUT 36 HOURS.
 
FORECASTER RAPPAPORT
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     30/0900Z 36.3N  53.5W    80 KTS
12HR VT     30/1800Z 38.3N  51.4W    75 KTS
24HR VT     01/0600Z 40.6N  47.6W    65 KTS
36HR VT     01/1800Z 42.9N  43.1W    60 KTS...EXTRATROPICAL
48HR VT     02/0600Z 45.4N  36.4W    50 KTS...EXTRATROPICAL
 
 
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