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| #111731 (Received by flhurricane at: 4:49 AM 19.Sep.2006) TCDAT3 HURRICANE HELENE DISCUSSION NUMBER 28 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006 500 AM EDT TUE SEP 19 2006 AS NOTED IN THE PREVIOUS DISCUSSION...THE CLOUD PATTERN ASSOCIATED WITH HELENE HAS BECOME ELONGATED NORTH TO SOUTH. A 0449 UTC AQUA MICROWAVE OVERPASS SUGGESTED THAT THE EYEWALL WAS OPEN TO THE SOUTHWEST...BUT THERE HAS BEEN LITTLE OVERALL CHANGE IN THE SATELLITE APPEARANCE AROUND THE CORE OF THE HURRICANE. DVORAK INTENSITY T-NUMBERS REMAIN 5.5 FROM ALL AGENCIES AND THE INITIAL INTENSITY WILL REMAIN 100 KT. CONDITIONS APPEAR FAVORABLE FOR FURTHER STRENGTHENING AS SHEAR IS FORECAST TO REMAIN LIGHT AND SSTS WARM. THE OFFICIAL INTENSITY FORECAST IS A LITTLE HIGHER THAN THE AVAILABLE GUIDANCE AND IT IS POSSIBLE THAT HELENE COULD BECOME A CATEGORY 4 HURRICANE DURING THE NEXT DAY OR TWO. THE ANTICIPATED WESTWARD MOTION APPEARS TO HAVE STARTED AS INDICATED BY AN INITIAL MOTION OF 285/7. IN FACT...THE MOTION OVER THE PAST FEW HOURS HAS BEEN NEARLY DUE WEST. THE DYNAMICAL MODELS AGREE ON A GENERAL WESTWARD MOVEMENT DURING THE NEXT 24 HOURS AS A MID-TROPOSPHERIC RIDGE TEMPORARILY BUILDS NORTH OF HELENE AS HURRICANE GORDON CONTINUES TO MOVE EASTWARD. THE GFDL MODEL ACTUALLY FORECASTS A SLIGHTLY SOUTH OF DUE WEST MOTION TODAY. IN A COUPLE OF DAYS...THE RIDGE IS FORECAST TO SHIFT EASTWARD AS A LARGE MID- TO UPPER-LEVEL TROUGH APPROACHES THE EAST COAST OF THE UNITED STATES. THIS SHOULD ALLOW THE HURRICANE TO TURN NORTHWARD AND EVENTUALLY NORTHEASTWARD AHEAD OF THIS TROUGH. THE OFFICIAL FORECAST IS VERY CLOSE TO THE PREVIOUS ADVISORY THROUGH 36 HOURS...THEREAFTER IT IS ADJUSTED A LITTLE EASTWARD CLOSE TO THE MODEL CONSENSUS AND THE GFDL TRACK. AT DAYS 4 AND 5...THE NHC FORECAST IS A LITTLE FASTER THAN THE PREVIOUS ADVISORY AND IS CLOSE TO THE GFS ENSEMBLE MEAN...BUT IT IS NOT AS FAST AS THE OPERATIONAL GFS OR GFDL MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 19/0900Z 24.4N 52.1W 100 KT 12HR VT 19/1800Z 24.6N 53.4W 105 KT 24HR VT 20/0600Z 25.1N 55.0W 110 KT 36HR VT 20/1800Z 26.4N 56.3W 110 KT 48HR VT 21/0600Z 28.3N 57.1W 110 KT 72HR VT 22/0600Z 33.6N 56.1W 100 KT 96HR VT 23/0600Z 38.0N 52.0W 90 KT 120HR VT 24/0600Z 42.0N 45.0W 80 KT $$ FORECASTER BROWN/STEWART |
