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HURRICANE MICHELLE DISCUSSION NUMBER 31
NATIONAL WEATHER SERVICE MIAMI FL
4 AM EST TUE NOV 06 2001
MICHELLE IS LOOKING LESS LIKE A TROPICAL CYCLONE AND MORE LIKE AN
EXTRATROPICAL LOW PRESSURE SYSTEM. HOWEVER...AN AIR FORCE HURRICANE
HUNTER AIRCRAFT AT 06/0520Z FOUND PEAK WINDS OF 106 KT IN THE
SOUTHEAST QUADRANT...SURROUNDED BY A LONG STRETCH OF 100+ KT WINDS.
MICHELLE ALSO HAS MAINTAINED A WARM-CORE STRUCTURE...SO IT IS BEING
KEPT AS A HURRICANE FOR THIS ADVISORY. SINCE THE MAXIMUM WINDS WERE
OBSERVED IN STRATIFORM CLOUDS OR IN THE CLEAR...A REDUCTION FACTOR
OF 70 PERCENT WAS USED...INSTEAD OF THE USUAL 90 PERCENT. THE NEXT
RECON FLIGHT WILL BE AT 18Z.
THE INITIAL MOTION IS 070/18. MICHELLE HAS REMAINED ON TRACK...SO
THERE IS LITTLE CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING.
WATER VAPOR IMAGERY INDICATES THAT MOST OF THE ENERGY ASSOCIATED
WITH THE DIGGING TROUGH OVER THE EASTERN U.S. IS GETTING STRETCHED
OUT TO THE NORTHEAST. THIS SHOULD HELP KEEP MICHELLE MOVING IN A
GENERAL EAST-NORTHEASTWARD DIRECTION...LIKE THE AVN IS INDICATING...
RATHER THAN LIFTING OUT TO THE NORTHEAST AND NORTH LIKE THE REST OF
THE GLOBAL MODELS ARE FORECASTING. THE OFFICIAL FORECAST IS JUST
SLIGHTLY SOUTH OF THE PREVIOUS FORECAST TRACK AND REMAINS CLOSE TO
THE AVN MODEL...WHICH IS ALONG THE SOUTHERN EDGE OF THE NHC GUIDANCE
SUITE.
DRY AIR IS PUNCHING IN ACROSS THE CENTER FROM THE SOUTHWEST AND THIS
HAS DISPLACED THE DEEP CONVECTION WELL TO THE SOUTHEAST OF THE
CENTER. AS A RESULT...MICHELLE IS EXPECTED TO GRADUALLY WEAKEN
THROUGHOUT THE FORECAST PERIOD. EVEN THOUGH MICHELLE IS LOOKING
MORE FRONTAL-LIKE...BAROCLINIC EFFECTS ASSOCIATED WITH THE DEEP
UPPER-LEVEL TROUGH OVER FLORIDA AND THE BAHAMAS MAY ACTUALLY HELP TO
KEEP THE INTENSITY UP LONGER THAN WE TYPICALLY SEE WITH SHEARED AND
CONVECTION-FREE TROPICAL CYCLONES...AND THIS IS INDICATED IN THE
INTENSITY FORECAST.
THE RADIUS OF MAXIMUM WINDS TO THE SOUTHEAST INCREASED OUT TO 120
NM...WHILE IT REMAINED CLOSE IN AT AROUND 45 NM TO THE NORTHWEST.
HURRICANE-FORCE WINDS ALSO EXTENDED OUTWARD MORE THAN 100 NM IN ALL
DIRECTIONS. THE WIND RADII WERE ADJUSTED ACCORDINGLY AND WERE BASED
ON DIFFERENT FLIGHT-LEVEL REDUCTION FACTORS ASSOCIATED WITHIN AND
OUTSIDE OF CONVECTION FOR THE VARIOUS QUADRANTS.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 06/0900Z 27.2N 71.7W 75 KTS
12HR VT 06/1800Z 28.0N 68.5W 65 KTS...BECOMING EXTRATROPICAL
24HR VT 07/0600Z 29.6N 63.6W 60 KTS...EXTRATROPICAL
36HR VT 07/1800Z 31.9N 58.7W 55 KTS...EXTRATROPICAL
48HR VT 08/0600Z 34.5N 54.2W 50 KTS...EXTRATROPICAL
72HR VT 09/0600Z 40.0N 44.0W 50 KTS...EXTRATROPICAL
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