417 
 WTNT43 KNHC 192051
 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