WTPA42 PHFO 091509
TCDCP2

TROPICAL STORM FELICIA DISCUSSION NUMBER  24
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP082009
500 AM HST SUN AUG 09 2009

HURRICANE FELICIA HAS SUFFERED SEVERE PROBLEMS WITH INCREASING 
VERTICAL WIND SHEAR DURING PAST SEVERAL HOURS. THE LATEST UW/CIMSS 
WIND SHEAR ANALYSIS INDICATES VALUES OF 257 DEG/21 KT. THE LATEST 
INFRARED SATELLITE IMAGERY AND HURRICANE RECONNAISSANCE AIRCRAFT 
DATA SHOW THE NEGATIVE AFFECTS OF THIS SHEAR. FOR EXAMPLE...THE LAST 
AIRCRAFT FIX AT 1115 UTC INDICATED THE CENTRAL PRESSURE HAD FILLED 
TO 994 MB...AND THE SURFACE CENTER WAS NO LONGER COLOCATED WITH THE 
FLIGHT-LEVEL CENTER BEFORE THEY DEPARTED THE WEAKENING TROPICAL 
CYCLONE. EARLIER...THEY FOUND THE HIGHEST FLIGHT-LEVEL WINDS WERE 72 
KT IN THE NORTHEAST QUADRANT AT 700 MB AROUND 0910 UTC. THESE 
AIRCRAFT DATA...ALONG WITH DVORAK CI NUMBERS OF 3.5 TO 4.0...AND AN 
ADT CI OF 3.1 AT 1200 UTC...INDICATE THAT FELICIA HAS WEAKENED TO A 
TROPICAL STORM WITH SUSTAINED WINDS OF 60 KT FOR THIS ADVISORY. NOT 
ONLY HAVE THE CLOUD TOPS OF FELICIA WARMED AND DECREASED IN 
COVERAGE...A PARTIALLY EXPOSED LOW- TO MID-LEVEL CIRCULATION CENTER 
HAS BECOME EVIDENT WEST OF THE REMAINING DEEP CONVECTION IN THE PAST 
COUPLE OF HOURS.
 
THE CURRENT MOTION OF FELICIA REMAINS 280/13...WHICH IS CLOSE TO THE 
PREVIOUS 18 HOUR MOTION. THE LATEST TRACK FORECAST HAS BEEN MODIFIED 
SLIGHTLY THROUGH 48 HOURS FROM THE PREVIOUS FORECAST TO SLOW THE 
FORWARD MOTION AND SHIFT THE TRACK SLIGHTLY TO THE LEFT FOLLOWING 
CLOSELY THE LATEST GFDI AND EDGING CLOSER TO MOST OF THE CONSENSUS 
MODELS. LITTLE SIGNIFICANT CHANGE WAS MADE IN THE TRACK FORECAST 
DURING 72-120 HOURS. THE LATEST OFFICIAL TRACK FORECAST CONTINUES 
DOWN THE CENTER OF THE GUIDANCE ENVELOPE...BUT REMAINS TO THE RIGHT 
OF THE CONSENSUS. NOTE...WITH THE TYPICAL 48 HOUR TRACK ERRORS...THE 
CENTER OF FELICIA COULD PASS OVER ANY PORTION OF THE MAIN HAWAIIAN 
ISLANDS DURING THE NEXT 2-3 DAYS.
 
FELICIA HAS BEGUN THE EXPECTED WEAKENING TREND. THE UNDERLYING
SEA-SURFACE TEMPERATURES REMAIN NEAR ABOUT 25 CELSIUS...BUT THESE
VALUES WILL GRADUALLY WARM ALONG THE FORECAST TRACK THROUGHOUT THE
FIVE-DAY FORECAST PERIOD. HOWEVER...WITH THE STRONG WESTERLY
VERTICAL WIND SHEAR CONTINUING...FELICIA SHOULD CONTINUE TO
WEAKEN. THE INTENSITY GUIDANCE MODELS RESPOND TO THESE FACTORS BY
FORECASTING STEADY WEAKENING...WITH SOME OF THEM BRINGING FELICIA
TO A TROPICAL DEPRESSION WITHIN 36 HOURS. THIS FORECAST HAS A
TROPICAL STORM THROUGH 48 HOURS...WHICH FOLLOWS THE GFDI.
 
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 40 PERCENT
CHANCE OF FELICIA BEING A TROPICAL STORM IN 48 HOURS WHEN IT IS
VERY NEAR THE HAWAIIAN ISLANDS...WITH ABOUT A 40 PERCENT CHANCE OF
IT BEING A TROPICAL DEPRESSION.
 
THERE IS A CHANCE THAT A TROPICAL STORM WARNING MAY BE NEEDED FOR
PARTS OF THE WATCH AREA LATER TODAY...SINCE THE LEAD TIME FOR
WATCHES IN THE CENTRAL PACIFIC BASIN IS 36 HOURS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/1500Z 20.6N 146.0W    60 KT
 12HR VT     10/0000Z 20.7N 148.0W    55 KT
 24HR VT     10/1200Z 20.8N 150.6W    45 KT
 36HR VT     11/0000Z 20.7N 153.0W    40 KT
 48HR VT     11/1200Z 20.5N 155.5W    35 KT
 72HR VT     12/1200Z 20.7N 160.3W    30 KT
 96HR VT     13/1200Z 21.5N 165.4W    25 KT...DISSIPATING
120HR VT     14/1200Z 22.3N 169.9W    20 KT...REMNANT LOW
 
$$
FORECASTER HOUSTON/WROE