778 
 WTPA42 PHFO 090258
 TCDCP2
 
 HURRICANE FELICIA DISCUSSION NUMBER  22
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP082009
 500 PM HST SAT AUG 08 2009
 
 THE SATELLITE PRESENTATION OF FELICIA HAS NOT CHANGED APPRECIABLY
 SINCE THE LAST AIR FORCE RECONNAISSANCE FIX AT ABOUT 2330 UTC...
 WHEN THE CENTRAL PRESSURE WAS MEASURED AT 982 MB.  THE EARLIER
 FLIGHT-LEVEL WINDS OF 85 KT AT 700 MB AROUND 2000 UTC...
 CORRESPONDING TO ABOUT 76 KT AT THE SURFACE...ALONG WITH DVORAK CI
 NUMBERS OF 4.5...PROVIDE THE BASIS FOR MAINTAINING THE ADVISORY
 INTENSITY AT 75 KT.  UPPER-LEVEL OUTFLOW APPEARS SLIGHTLY
 RESTRICTED IN THE SOUTHWESTERN SEMICIRCLE...BUT NOT ENOUGH TO
 SUGGEST THAT WIND SHEAR IS HAVING ANY EFFECT ON THE CYCLONE YET.
 
 THE LONG-TERM HEADING OVER A 12-HOUR PERIOD IS ABOUT 285-290
 DEGREES...BUT THE LAST COUPLE OF AIRCRAFT FIXES AND RECENT GOES
 SATELLITE IMAGERY SUGGEST AN INITIAL MOTION THAT IS JUST NORTH OF
 DUE WEST AT ABOUT 13 KT.  SOME OF THE MODELS...SUCH AS THE GFS AND
 HWRF...FORECAST FELICIA TO GAIN A LITTLE MORE LATITUDE BEFORE
 TURNING DUE WEST...WHILE MOST OF THE OTHERS CALL FOR THE HURRICANE
 TO MOVE AT 270 DEGREES WITHIN THE NEXT FEW HOURS.  BEYOND 24 HOURS
 OR SO...ALL OF THE GUIDANCE AGREES ON A DUE WESTWARD HEADING ALONG
 THE SOUTHERN PERIPHERY OF A LOW- TO MID-LEVEL RIDGE...WITH TRACKS
 CROSSING HAWAII AT SLIGHTLY DIFFERENT LATITUDES.  THE NEW OFFICIAL
 TRACK FORECAST GOES DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE AND
 REPRESENTS A SLIGHT NORTHWARD ADJUSTMENT FROM THE PREVIOUS
 ADVISORY.  SINCE THERE ARE RELIABLE MODELS ON EITHER SIDE OF THE
 OFFICIAL FORECAST...THE CENTER OF FELICIA COULD PASS OVER ANY
 PORTION OF THE MAIN HAWAIIAN ISLANDS DURING THE NEXT 2-3 DAYS.
 
 FELICIA IS TAKING ITS TIME TO EMBARK UPON A SERIOUS WEAKENING TREND. 
 THE UNDERLYING SEA-SURFACE TEMPERATURES ARE CURRENTLY ABOUT 25
 CELSIUS AND WILL GRADUALLY WARM ALONG THE FORECAST TRACK THROUGHOUT
 THE FIVE-DAY FORECAST PERIOD.  MEANWHILE...WESTERLY SHEAR IS
 FORECAST TO SLOWLY INCREASE AND MAXIMIZE IN ABOUT 48 HOURS...ABOUT
 THE TIME FELICIA IS ON THE DOORSTEP OF THE HAWAIIAN ISLANDS.  THE
 INTENSITY GUIDANCE MODELS RESPOND TO THESE FACTORS BY FORECASTING
 GRADUAL WEAKENING...BUT ALL OF THEM HOLD ON TO A TROPICAL STORM
 THROUGH 48 HOURS...AND SOME EVEN TO 72 HOURS.  THE NEW OFFICIAL
 FORECAST IS ADJUSTED SLIGHTLY UPWARD FROM THE PREVIOUS ONE TO BE
 CONSISTENT WITH THE INTENSITY CONSENSUS...ICON.
 
 GIVEN THE UNCERTAINTIES WITH INTENSITY FORECASTING...IT IS IMPORTANT
 TO POINT OUT THE INTENSITY PROBABILITIES ACCOMPANYING THIS ADVISORY
 PACKAGE.  THAT PRODUCT INDICATES THAT THERE IS ABOUT A 60 PERCENT
 CHANCE OF FELICIA BEING A TROPICAL STORM IN 48 HOURS WHEN IT IS
 VERY NEAR THE HAWAIIAN ISLANDS...WITH ABOUT A 25 PERCENT CHANCE OF
 IT BEING A TROPICAL DEPRESSION...AND A 10 PERCENT CHANCE OF IT
 BEING A HURRICANE.
 
 THE NEW FORECAST NECESSITATES THE ISSUANCE OF A TROPICAL STORM WATCH
 FOR PORTIONS OF THE HAWAIIAN ISLANDS...SINCE THE LEAD TIME FOR
 WATCHES IN THE CENTRAL PACIFIC BASIN IS 48 HOURS.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      09/0300Z 20.1N 143.4W    75 KT
  12HR VT     09/1200Z 20.4N 145.4W    65 KT
  24HR VT     10/0000Z 20.5N 148.2W    60 KT
  36HR VT     10/1200Z 20.5N 151.0W    55 KT
  48HR VT     11/0000Z 20.5N 153.7W    45 KT
  72HR VT     12/0000Z 20.5N 159.0W    35 KT
  96HR VT     13/0000Z 21.0N 164.5W    30 KT
 120HR VT     14/0000Z 22.0N 170.0W    30 KT
  
 $$
 FORECASTER KNABB/R BALLARD