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TROPICAL STORM MICHELLE DISCUSSION NUMBER 10
NATIONAL WEATHER SERVICE MIAMI FL
10 PM EST WED OCT 31 2001
AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT FOUND 1500 FT
FLIGHT-LEVEL WINDS OF 42 KT LOCATED NORTHWEST AND SOUTHEAST OF THE
CENTER OF THE BROAD CIRCULATION. THIS EQUATES TO ABOUT 36 KT AT THE
SURFACE...SO TROPICAL DEPRESSION FIFTEEN HAS BEEN UPGRADED TO
TROPICAL STORM MICHELLE. THE LOW-LEVEL CENTER IS LOCATED ALONG THE
SOUTHERN EDGE OF THE DEEP CONVECTION OWING TO THE SOUTHERLY
UPPER-LEVEL SHEAR. HOWEVER...THE CENTRAL DEEP CONVECTION AND
ASSOCIATED BANDING FEATURES HAVE CONTINUED TO IMPROVE OVER THE PAST
4 HOURS SINCE THE LAST RECON FLIGHT. UPPER-LEVEL OUTFLOW REMAINS
QUITE IMPRESSIVE IN THE NORTHERN SEMICIRCLE AND IS ALSO SHOWING
SIGNS OF BECOMING LESS RESTRICTED TO THE SOUTH.
THE INITIAL MOTION ESTIMATE IS 350/5. THE APPARENT NORTHWARD JUMP
IN THE CENTER POSITION IS PRIMARILY DUE TO REFORMATION FARTHER NORTH
NEAR THE DEEP CONVECTION...WHICH HAS BEEN THE HISTORY OF THIS
CYCLONE DURING THE PAST 48 HOURS. HOWEVER...DROPSONDE DATA FROM THE
GULFSTREAM-IV AIRCRAFT INDICATES THAT THERE IS A NARROW BREAK IN THE
SUBTROPICAL RIDGE...BASED ON A TROUGH AXIS THAT EXTENDS FROM
MICHELLE NORTH-NORTHWESTWARD TO WESTERN CUBA. ONLY THE 18Z AVN
MODEL PICKED UP ON THIS SUBTLE FEATURE. THE CURRENT POSITION AND
STRENGTH OF THE RIDGE TO THE EAST OF THE CYCLONE IS FORECAST TO
REMAIN STEADY THROUGHOUT THE PERIOD. THEREFORE...MICHELLE IS
EXPECTED TO TRACK SLOWLY UP THE TROUGH IN A NORTHWARD OR
NORTH-NORTHWESTWARD DIRECTION TOWARD WESTERN CUBA. THE OFFICIAL
FORECAST IS A LITTLE TO THE RIGHT OF THE PREVIOUS FORECAST
TRACK...BUT ONLY DUE TO THE MORE EASTWARD POSITION OF THE CENTER
BASED ON THE RECON DATA. THIS SCENARIO IS ALSO CONSISTENT WITH THE
18Z AVN MODEL. THE UKMET AND NOGAPS MODEL SOLUTIONS OF TAKING
MICHELLE WEST-NORTHWESTWARD INTO THE YUCATAN PENINSULA WERE NOT
CONSIDERED SINCE THEY KEEP THE CYCLONE VERY WEAK...WHICH ALLOWS THE
LOW-LEVEL STEERING FLOW TO DRIVE THE STORM MORE WESTWARD.
NOW THAT THE CENTER OF MICHELLE IS FINALLY OVER WARM WATER...STEADY
INTENSIFICATION SHOULD OCCUR IN SPITE OF THE SOUTHERLY SHEAR ON THE
SYSTEM. THE SHIPS INTENSITY MODEL WAS FOLLOWED CLOSELY...WHICH
BRINGS MICHELLE TO HURRICANE STRENGTH IN 48 HOURS. HOWEVER...MY
BIGGEST CONCERN IS THAT THE LOW-LEVEL CENTER MAY TUCK IN UNDERNEATH
THE DEEP CONVECTION SOONER THAN EXPECTED...WHICH IS WHAT THE LATEST
SATELLITE DATA SUGGESTS MAY BE HAPPENING. THIS WOULD ALLOW FOR MORE
STRENGTHENING THAN IS CURRENTLY INDICATED. RAPID INTENSIFICATION IS
ALSO A DISTINCT POSSIBILITY GIVEN THE FAVORABLE UPPER-LEVEL OUTFLOW
PATTERN AND VERY WARM SSTS CURRENTLY EXISTING ACROSS THE NORTHWEST
CARIBBEAN SEA. RECENT HISTORY INDICATES THAT THIS IS THE SAME
PATTERN THAT PRODUCED HURRICANES MITCH AND LENNY IN THIS SAME AREA.
THERE CONTINUES TO BE A MAJOR DISAGREEMENT BETWEEN MODEL TRACK
FORECASTS AFTER 72 HR...THEREFORE IT IS TOO EARLY TO SPECULATE IF
ANY PORTION OF THE UNITED STATES WILL BE THREATENED BY THIS SYSTEM.
STAY TUNED. HOWEVER...IF MICHELLE TRACKS SLIGHTLY FASTER THAN
FORECAST...THEN IT COULD REACH THE SOUTHEAST GULF OF MEXICO BEFORE
THE NEXT BLOCKING SURFACE HIGH PRESSURE SYSTEM CAN TURN TO THE EAST
LIKE THE AVN MODEL IS INDICATING BY AROUND 72 HOURS.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 01/0300Z 16.1N 83.2W 35 KTS
12HR VT 01/1200Z 16.8N 83.4W 40 KTS
24HR VT 02/0000Z 18.0N 83.8W 45 KTS
36HR VT 02/1200Z 18.9N 84.1W 55 KTS
48HR VT 03/0000Z 20.0N 84.4W 65 KTS
72HR VT 04/0000Z 22.0N 84.5W 75 KTS
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