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TROPICAL STORM HELENE DISCUSSION NUMBER 17
NATIONAL WEATHER SERVICE MIAMI FL
10 AM CDT FRI SEP 22 2000
THE CENTER OF HELENE MADE LANDFALL NEAR FT. WALTON BEACH FLORIDA
NEAR 12Z AND IS NOW MOVING 030/11 ACROSS THE WESTERN PANHANDLE. A
RECENT BURST OF STRONG CONVECTION NEAR THE CENTER SHOWED A VERY
IMPRESSIVE VELOCITY SIGNATURE ON THE EGLIN AFB WSR-88D...AND OTHER
MESOCYCLONES HAVE BEEN SEEN IN STRONG BANDS FURTHER TO THE EAST.
THE VELOCITY DISPLAYS FROM THE EGLIN AND TALLAHASSEE WSR-88DS
INDICATE WINDS OF 45-50 KT ALOFT IN THE CONVECTIVE BANDS...SO HELENE
REMAINS A 35 KT STORM FOR THIS PACKAGE.
THERE ARE NO SURPRISES IN THE TRACK FORECAST OR TRACK GUIDANCE.
HELENE IS RECURVING INTO THE WESTERLIES AND SHOULD GRADUALLY
ACCELERATE TO THE EAST-NORTHEAST OVER THE NEXT 72 HR. GUIDANCE
AGREES WITH THIS SCENARIO...EXCEPT FOR THE UKMET WHICH TAKES HELENE
NORTH AND DISSIPATES IT.
HELENE SHOULD WEAKEN FOR THE NEXT 24 TO 36 HR WHILE OVER LAND. IF
IT SURVIVES PAST THAT...SOME OF THE LARGE-SCALE GUIDANCE SUGGESTS
THE POSSIBILITY OF RE-INTENSIFICATION AS A EXTRATROPICAL SYSTEM AS
IT MOVES INTO THE ATLANTIC. GIVEN THE LACK OF ANY OBVIOUS
BAROCLINIC FORCING IN THE MODELS THIS LOOKS A LITTLE DUBIOUS.
HOWEVER...THE INTENSITY FORECAST WILL CALL FOR SOME STRENGTHENING AT
THAT TIME IN COORDINATION WITH THE MARINE PREDICTION CENTER.
EVEN THOUGH HELENE WILL WEAKEN OVER LAND...A COMBINATION OF THE
CYCLONE AND AN OLD FRONTAL BOUNDARY TO THE NORTH SHOULD CONTINUE
SPREADING HEAVY RAINS ACROSS THE SOUTHEASTERN UNITED STATES FOR THE
NEXT 48 HR OR SO.
FORECASTER BEVEN
FORECAST POSITIONS AND MAX WINDS
INITIAL 22/1500Z 30.9N 86.1W 35 KTS...INLAND
12HR VT 23/0000Z 32.6N 84.6W 30 KTS...INLAND
24HR VT 23/1200Z 34.6N 81.3W 25 KTS...INLAND
36HR VT 24/0000Z 36.4N 77.1W 25 KTS...INLAND
48HR VT 24/1200Z 38.5N 72.0W 35 KTS...EXTRATROPICAL
72HR VT 25/1200Z 44.0N 60.0W 35 KTS...EXTRATROPICAL
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