704 
 WTNT43 KNHC 230230
 TCDAT3
 TROPICAL STORM HELENE DISCUSSION NUMBER  43
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
 1100 PM EDT FRI SEP 22 2006
  
 HELENE IS LOOKING SOMEWHAT LESS TROPICAL IN SATELLITE IMAGERY THIS
 EVENING.  ONLY LIMITED DEEP CONVECTION REMAINS NEAR THE CENTER...
 WITH THE BULK OF THE COLDER TOPS NOW WELL TO THE NORTH AND
 NORTHWEST OF THE CENTER.  SATELLITE INTENSITY ESTIMATES ARE 65 KT
 FROM TAFB...55 KT FROM AFWA...AND EXTRATROPICAL FROM SAB.  QUIKSCAT
 DATA FROM 22Z SHOWED 50-60 KT WINDS SOUTHEAST OF THE CENTER...WITH
 ONE QUESTIONABLE-LOOKING 65 KT VECTOR IN THE SOUTHWEST QUADRANT. 
 BASED ON THE AVAILABLE DATA...HELENE IS DOWNGRADED TO A 60-KT
 TROPICAL STORM.  THE INITIAL AND FORECAST WIND RADII HAVE BEEN
 EXPANDED CONSIDERABLY BASED ON THE QUIKSCAT DATA.
 
 HELENE TURNED TO THE RIGHT BETWEEN 18Z AND 00Z...BUT SINCE THEN
 LOOKS LIKE IT MAY BE TURNING BACK TO THE LEFT.  THE INITIAL MOTION
 IS A SOMEWHAT UNCERTAIN 070/20.  HELENE SHOULD CONTINUE GENERALLY
 EAST-NORTHEASTWARD TO NORTHEASTWARD FOR 72 HR IN DEEP SOUTHWESTERLY
 FLOW.  AFTER THAT TIME...THERE IS SERIOUS DIVERGENCE IN THE MODEL
 FORECASTS.  THE 12Z ECMWF...THE 18Z GFS...AND THE 18Z NOGAPS ALL
 TURN HELENE SOUTHWARD AND PASS NEAR OR OVER THE AZORES.  ON THE
 OTHER HAND...THE 12Z UKMET...THE 18Z GFDL...AND THE 18Z GFS
 ENSEMBLE-MEAN ALL FORECAST HELENE TO CONTINUE NORTHEASTWARD.  SINCE
 THE 18Z GFS AND NOGAPS RUNS SHOW MAJOR CHANGES FROM THEIR PREVIOUS
 RUNS THAT TOOK HELENE NORTHEASTWARD...IT IS TOO SOON TO MAKE MAJOR
 CHANGES TO THE FORECAST TRACK.  THUS...THE NEW TRACK CALLS FOR A
 CONTINUED NORTHEASTWARD MOTION AFTER 72 HR.  THE NEW TRACK IS SOUTH
 OF THE PREVIOUS TRACK AND IN BEST AGREEMENT WITH THE UKMET.
 
 SATELLITE IMAGERY SHOWS COLD AIR STRATOCUMULUS CLOUDS WEST OF THE
 CENTER...SUGGESTING THE THE COLD FRONT THAT THE LARGE-SCALE MODELS
 HAVE BEEN FORECASTING TO INTERACT WITH THE STORM MAY BE A LITTLE
 STRONGER THAN PREVIOUSLY EXPECTED.  THIS HAS LED TO AN EARLIER
 EXTRATROPICAL TRANSITION THAN FORECAST 24-48 HR AGO.  ALTHOUGH THE
 LARGE-SCALE MODEL GUIDANCE SUGGESTS THAT HELENE MAY KEEP A WARM
 CORE OF SOME TYPE FOR THE NEXT 3-4 DAYS...IT IS EXPECTED THAT
 ENOUGH COLD AIR WILL ENTRAIN INTO THE STORM TO COMPLETE
 EXTRATROPICAL TRANSITION IN 12-24 HR.  HELENE WILL LIKELY
 STRENGTHEN SOME AS AN EXTRATROPICAL LOW THROUGH 36 HR...THEN
 GRADUALLY WEAKEN THEREAFTER.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      23/0300Z 36.0N  50.6W    60 KT
  12HR VT     23/1200Z 37.0N  47.1W    60 KT...BECOMING EXTRATROPICAL
  24HR VT     24/0000Z 38.5N  42.6W    65 KT...EXTRATROPICAL
  36HR VT     24/1200Z 40.0N  38.0W    65 KT...EXTRATROPICAL
  48HR VT     25/0000Z 42.1N  33.7W    60 KT...EXTRATROPICAL
  72HR VT     26/0000Z 45.5N  26.0W    55 KT...EXTRATROPICAL
  96HR VT     27/0000Z 49.0N  18.0W    45 KT...EXTRATROPICAL
 120HR VT     28/0000Z 53.0N  12.0W    40 KT...EXTRATROPICAL
  
 $$
 FORECASTER BEVEN