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| #111871 (Received by flhurricane at: 4:55 PM 19.Sep.2006) TCDAT3 HURRICANE HELENE DISCUSSION NUMBER 30 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006 ISSUED BY THE HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 500 PM EDT TUE SEP 19 2006 A NOAA AIRCRAFT MADE A COUPLE OF PASSES THROUGH HURRICANE HELENE EARLY THIS AFTERNOON. THE ESTIMATED PRESSURE OF 960 MB THIS MORNING APPEARED CORRECT AS THE PLANE MEASURED 958 MB BEFORE DEEPENING ANOTHER 2 MB AN HOUR LATER. THE MAX FLIGHT LEVEL WIND WAS 98 KNOTS AT 850 MB IN THE NORTHWEST QUADRANT AND TWO EYE WALLS WERE PRESENT... 40NM AND 120NM OUT RESPECTIVELY. MICROWAVE SATELLITE DATA ALSO INDICATED THESE TWO EYEWALL FEATURES THIS MORNING. DESPITE THE PRESSURE LOWERING SLIGHTLY... THE 90 PERCENT REDUCTION RULE CONCERNING MAX FLIGHT LEVEL WINDS SUGGESTS A 95 KNOT HURRICANE. PLUS... THIS PRESENT EYEWALL CYCLE WOULD SUGGEST SLIGHT FILLING OF THE CYCLONE AND THE WINDS LIKELY BROADENING THROUGHOUT THE SYSTEM. OTHERWISE HELENE SHOWS TRUE SYMMETRY... A DEEP CENTRAL DENSE OVERCAST AND A WELL-DEFINED EYE FEATURE ALL INDICATIVE OF A MATURE HURRICANE UNDERGOING FLUCTUATIONS IN INTENSITY. THE INITIAL MOTION IS 300 DEGREES AT 8 KTS AND THIS MOTION SHOULD PERSIST INTO WEDNESDAY MORNING. THE TRACK FORECAST REMAINS VERY CONSISTENT... A QUICK RECURVATURE TO THE NORTH... EVENTUALLY OFF TO THE NORTHEAST AND PICKING UP FORWARD MOMENTUM. THE GLOBAL MODELS AND OBJECTIVE AIDS SUGGEST THIS AS THE UPPER LOW AND AMPLIFIED UPPER TROUGH UPSTREAM NEAR THE EAST COAST BREAKS DOWN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC. HELENE SHOULD BEGIN THIS NORTHWARD TREND DURING THE DAY ON WEDNESDAY AND BEFORE REACHING 60W LONGITUDE. HPC GENERALLY FOLLOWED THE TIGHTLY CLUSTERED OPERATIONAL RUNS OF THE GFS/GFDL AND UKMET ALONG WITH DYNAMICAL GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 19/2100Z 24.6N 54.1W 95 KT 12HR VT 20/0600Z 25.2N 55.2W 95 KT 24HR VT 20/1800Z 26.7N 56.5W 100 KT 36HR VT 21/0600Z 28.9N 56.8W 95 KT 48HR VT 21/1800Z 32.0N 56.3W 90 KT 72HR VT 22/1800Z 39.0N 51.5W 90 KT 96HR VT 23/1800Z 45.3N 41.0W 80 KT 120HR VT 24/1800Z 49.0N 30.5W 70 KT EXTRATROPICAL $$ FORECASTER MUSHER |
