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