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| #111096 (Received by flhurricane at: 11:03 PM 15.Sep.2006) TCDAT3 TROPICAL STORM HELENE DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006 1100 PM EDT FRI SEP 15 2006 THE INITIAL MOTION ESTIMATE IS 300/12. HELENE APPEARS TO BE ON TRACK BASED ON A PLETHORA OF MICROWAVE SATELLITE DATA. THE INITIAL POSITION...HOWEVER...IS SOUTH OF THE CONVENTIONAL SATELLITE FIXES WHICH APPEAR TO BE A REFLECTION OF A MID-LEVEL CIRCULATION CENTER. MICROWAVE DATA SUGGESTS THAT THE ADVISORY MAY BE A LITTLE TOO FAR TO THE NORTH...BUT CONTINUITY WITH THE PREVIOUS FORECAST TRACK WAS FOLLOWED GIVEN THAT HELENE STILL HAS A BROAD LOW-LEVEL CIRCULATION AND REDEVELOPMENT OF THE CENTER FARTHER NORTH IS STILL POSSIBLE. OTHERWISE...THERE REMAINS LITTLE CHANGE TO THE PREVIOUS SEVERAL FORECAST TRACKS AND REASONINGS. THE MODELS REMAIN IN EXCELLENT AGREEMENT ON A STEADY WEST-NORTHWESTWARD MOTION FOR THE NEXT 72 HOURS. AFTER THAT...THE MODELS DIVERGE QUITE SIGNIFICANTLY WITH THE GFDL TAKING HELENE MORE NORTHWARD...WHILE THE NOGAPS MODEL TAKES THE CYCLONE MORE WESTWARD. THE REST OF THE MODELS ARE SPREAD OUT EVENLY BETWEEN THOSE TWO EXTREMES. HOWEVER...ALL THE MODELS AGREE THAT A STRONG SHORTWAVE TROUGH CURRENTLY OVER THE NORTHEASTERN U.S. WILL MOVE SOUTHEAST AND THEN EASTWARD AND WEAKEN THE STEERING FLOW AHEAD OF HELENE BY 96 AND 120 HOURS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK AND THE NHC MODEL CONSENSUS. THE OUTFLOW PATTERN REMAINS GOOD IN ALL QUADRANTS...WHICH USUALLY FAVORS STEADY INTENSIFICATION. HOWEVER...DRY AIR IS STILL BEING ENTRAINED INTO THE CENTER OF THE CYCLONE AS NOTED IN MICROWAVE IMAGERY...SO ONLY SLOW INTENSIFICATION IS EXPECTED FOR THE NEXT 24 HOURS. AFTER THAT...DECREASING VERTICALLY SHEAR AND INCREASING SSTS SHOULD LEAD TO MORE SIGNIFICANT INTENSIFICATION AND HELENE COULD BECOME A MAJOR HURRICANE BY 72 HOURS...AND POSSIBLY THROUGH 120H. FORECAST POSITIONS AND MAX WINDS INITIAL 16/0300Z 17.2N 43.7W 60 KT 12HR VT 16/1200Z 17.9N 45.1W 65 KT 24HR VT 17/0000Z 18.9N 46.7W 70 KT 36HR VT 17/1200Z 19.8N 48.1W 75 KT 48HR VT 18/0000Z 20.7N 49.4W 90 KT 72HR VT 19/0000Z 22.4N 51.8W 100 KT 96HR VT 20/0000Z 24.0N 54.6W 100 KT 120HR VT 21/0000Z 26.0N 57.0W 95 KT $$ FORECASTER STEWART |
