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TROPICAL STORM ALLISON DISCUSSION NUMBER 2
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT TUE JUN 05 2001
REPORTS THIS AFTERNOON FROM AN AIR FORCE RESERVE RECONNAISSANCE
AIRCRAFT INDICATE THE BROAD CIRCULATION OF ALLISON HAS MOVED LITTLE.
ALSO...SATELLITE AND SURFACE OBSERVATIONS INDICATE SEVERAL SMALLER
VORTICES HAVE MOVED OUT FROM UNDER THE DEEP CONVECTION TOWARD THE
TEXAS COAST SOUTH OF GALVESTON...WHICH HAS COMPLICATED THE LOCATION
ESTIMATE PROCESS. THE ADVISORY POSITION HAS BEEN ADJUSTED WEST OF
THE PREVIOUS LOCATION...BUT JUST EAST OF THE RECON POSITIONS BASED
ON SYNOPTIC ANALYSES OF THE BROADER LOW-LEVEL CIRCULATION.
INITIAL MOTION ESTIMATE IS 360/10. THERE IS NO SIGNIFICANT CHANGE
TO PREVIOUS TRACK PHILOSOPHY OTHER THAN TO SHIFT THE TRACK A LITTLE
TO THE LEFT BASED ON THE WESTWARD REPOSITIONING OF THE BROAD
LOW-LEVEL CIRCULATION CENTER. TROPICAL STORM ALLISON IS EXPECTED TO
CONTINUE MOVING NORTHWARD AROUND THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE...WHICH IS FORECAST TO REMAIN ORIENTED EAST-WEST
ACROSS THE SOUTHERN U.S. FROM GEORGIA TO LOUISIANA THROUGH THE
FORECAST PERIOD. THE BROAD CENTER SHOULD MOVE INLAND OVER EXTREME
SOUTHEAST TEXAS OR SOUTHWEST LOUISIANA LATER TONIGHT AND THEN TURN
MORE TOWARD THE NORTHEAST AS A SHORTWAVE TROUGH OVER THE SOUTHERN
PLAINS GRADUALLY PICKS UP THE SYSTEM. THIS SCENARIO IS CONSISTENT
WITH MOST OF THE GLOBAL MODELS.
SOME SLIGHT STRENGTHENING IS POSSIBLE BEFORE LANDFALL EVEN THOUGH
ALLISON IS A HYBRID SYSTEM. HOWEVER...IT IS UNLIKELY THAT THE
CYCLONE WOULD GET ABOVE 55 KT DUE TO THE COOL OFFSHORE SEA SURFACE
TEMPERATURES. THE INTENSITY WAS HELD UP SLIGHTLY AT 12 HOURS EVEN
THOUGH THE SYSTEM CENTER IS EXPECTED TO BE INLAND. THIS IS DUE TO
THE LONG FETCH OF SOUTHEASTERLY TROPICAL STORM FORCE WINDS TO STILL
BE SPREADING ONSHORE THE LOUISIANA COAST AT THAT TIME.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 05/2100Z 28.8N 95.1W 50 KTS
12HR VT 06/0600Z 30.4N 95.1W 45 KTS...INLAND
24HR VT 06/1800Z 32.2N 94.8W 30 KTS...INLAND DISSIPATING
36HR VT 07/0600Z 33.6N 93.9W 25 KTS...INLAND DISSIPATING
48HR VT 07/1800Z 34.5N 92.6W 20 KTS...INLAND DISSIPATING
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