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| #111377 (Received by flhurricane at: 10:37 AM 17.Sep.2006) TCDAT3 HURRICANE HELENE DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006 1100 AM EDT SUN SEP 17 2006 VISIBLE SATELLITE IMAGES SHOW THAT HELENE HAS DEVELOPED A LARGE RAGGED EYE SURROUNDED BY A RING OF DEEP CONVECTION. SATELLITE INTENSITY ESTIMATES FROM ALL AGENCIES HAVE INCREASED TO 5.0 ON THE DVORAK SCALE. THE 3-HOUR AVERAGE ADVANCED OBJECTIVE TECHNIQUE FROM THE UNIVERSITY OF WISCONSIN IS 5.6. ON THIS BASIS...THE INITIAL INTENSITY HAS BEEN INCREASED TO 90 KNOTS. THERE IS A CHANCE FOR AN ADDITIONAL STRENGTHENING DURING THE NEXT DAY OR TWO BEFORE THE SHEAR INCREASES AS SUGGESTED BY SHIPS MODEL. THE OCEAN IS EXPECTED TO REMAIN WARM ALONG THE FORECAST TRACK. HELENE IS MOVING TOWARD THE NORTHWEST OR 305 DEGREES AT 9 KNOTS. THE FORECAST SCENARIO COULD BE DESCRIBED AS SUCH...HELENE CURRENTLY LOCATED ON THE SOUTHWESTERN EDGE A SUBTROPICAL RIDGE AND MOVING TOWARD A WEAKNESS CAUSED BY A SHARP MID-LEVEL SHORT WAVE JUST EAST OF THE UNITED STATES CAST. THEN...AS THE SHORT WAVE MOVES OUT THE AREA...THE RIDGE WILL LIKELY BUILD WESTWARD FORCING HELENE TO TEMPORARILY TURN MORE TO THE WEST-NORTHWEST. AFTER 3 DAYS...A LARGER TROUGH IS EXPECTED TO MOVE EASTWARD AND FINALLY PICK UP HELENE. THE DILEMMA IS HOW FAR WEST WILL HELENE GO SINCE TWO GOOD MODELS DIVERGE...PUTTING ME BETWEEN A ROCK AND HARD PLACE. THE GOOD GFS AND THE GFS ENSEMBLE MEAN HAVE THE WESTERNMOST SOLUTIONS WHILE THE OUTSTANDING AND HARD TO BEAT GFDL HAS HELENE TURNING NORTHWARD FARTHER EAST. SINCE THE REST OF THE GUIDANCE IS IN BETWEEN THESE TWO EXTREME OPTIONS...THE OFFICIAL FORECAST DOES IT AS WELL. FORECAST POSITIONS AND MAX WINDS INITIAL 17/1500Z 20.5N 49.0W 90 KT 12HR VT 18/0000Z 21.3N 50.1W 95 KT 24HR VT 18/1200Z 22.5N 51.5W 100 KT 36HR VT 19/0000Z 23.0N 53.0W 100 KT 48HR VT 19/1200Z 23.5N 54.5W 95 KT 72HR VT 20/1200Z 24.5N 57.0W 90 KT 96HR VT 21/1200Z 27.0N 59.0W 85 KT 120HR VT 22/1200Z 30.0N 59.5W 80 KT $$ FORECASTER AVILA |
