WTPA42 PHFO 101502 TCDCP2 TROPICAL STORM FELICIA DISCUSSION NUMBER 28 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP082009 500 AM HST MON AUG 10 2009 DESPITE THE FACT THAT THERE IS STILL DEEP CONVECTION ASSOCIATED WITH TROPICAL STORM FELICIA...THE REMAINING CLUSTER OF THUNDERSTORMS IS ALMOST 100 NM NORTHEAST OF THE EXPOSED LOW-LEVEL CIRCULATION CENTER...OR LLCC. THEREFORE...THE LLCC APPEARS TO BE DECOUPLED FROM THE REMAINING DEEP CONVECTION DUE TO THE STRONG WESTERLY VERTICAL WIND SHEAR IN EXCESS OF 30 KT ACCORDING TO THE 1200 UTC UW/CIMSS ESTIMATE. THE LATEST U.S. AIR FORCE RESERVES RECONNAISSANCE AIRCRAFT FLIGHT DATA...IN ADDITION TO DATA FROM QUIKSCAT AND ASCAT PASSES FROM LAST EVENING...INDICATE TROPICAL STORM FORCE WINDS CONTINUED OVER A BROAD AREA IN THE NORTHERN SEMICIRCLE OF FELICIA. THE LAST AIRCRAFT FIX IN THE SYSTEM AT 1103 UTC INDICATED THE CENTRAL PRESSURE WAS AROUND 1005 MB BASED ON A DROPSONDE. EVEN THOUGH A MAXIMUM FLIGHT-LEVEL WIND OF 59 KT AT 850 MB WAS OBSERVED EARLIER IN THE FLIGHT AROUND 0854 UTC...THIS OBSERVATION WAS MADE IN THE NORTHEAST QUADRANT IN THE DEEP CONVECTION. THIS INCREASING SEPARATION OF THESE THUNDERSTORMS FROM THE LLCC MAKE IT DIFFICULT TO BELIEVE FELICIA STILL HAS THESE STRONG WINDS. BASED ON THESE EARLIER AIRCRAFT MEASUREMENTS AND DVORAK CI NUMBERS FROM PHFO...JTWC AND SAB RANGING FROM 2.0 TO 2.5...THE INITIAL INTENSITY IS REDUCED TO 40 KT FOR THIS FORECAST PACKAGE. THE AIRCRAFT FIXES BETWEEN 0500 AND 1100 UTC...ALONG WITH LOOPS OF INFRARED SATELLITE IMAGERY SUPPORT THE CURRENT MOTION OF 260 DEG AT 10 KT. SINCE THE TROPICAL STORM IS A SHEARED SYSTEM...ITS MOTION WILL PRIMARILY BE CONTROLLED BY THE LOW-LEVEL EASTERLY FLOW SOUTH OF THE SUBTROPICAL RIDGE TO THE NORTH. THE LATEST TRACK FORECAST CONTINUES TO BRING FELICIA ACROSS THE MID-SECTION OF THE STATE. WITH AN INITIAL MOTION JUST SOUTH OF DUE WEST...THE TRACK WAS SHIFTED TO THE LEFT OF THE PREVIOUS FORECAST...WITH LITTLE VARIATION IN THE ALONG TRACK MOTION THROUGH 48 HOURS. THIS SHIFT FOLLOWS CLOSELY THE GFDL...HWRF AND TRACK CONSENSUS MODELS...WHICH ALSO SHOWED A SHIFT TO THE LEFT THROUGH THE 36 TO 48 HOUR PERIOD. NOTE THAT THERE IS STILL A POSSIBILITY THAT THE DECOUPLED LLCC MAY CONTINUE TO STEER MORE TOWARD THE WEST SOUTHWEST THAN IS ANTICIPATED. IF SO...FELICIA MAY BE STEERED DIRECTLY INTO THE BIG ISLAND. THE GFS MODEL...AND THEREFORE THE BAMS AND BAMM MODELS...CONTINUE TO BRING FELICIA NORTH OF THE HAWAIIAN ISLANDS. THIS SEEMS DIFFICULT TO BELIEVE AT THIS POINT... BUT IT DOES KEEP THE CURRENT FORECAST IN THE MIDDLE OF THE GUIDANCE AT THIS TIME. FELICIA IS BEGINNING TO MOVE WESTWARD AWAY FROM THE THE UPPER LEVEL DIFFLUENCE. THEREFORE...THE SUPPORT FOR THE DEEP CONVECTION NORTHEAST OF THE LLCC APPEARS TO BE DECREASING. AS FELICIA MOVES EVEN FARTHER WEST...IT WILL NO LONGER BE IN THIS AREA OF DIFFLUENCE ALOFT. THEREFORE...THE UPPER LEVEL WESTERLY WINDS WILL CONTINUE TO PRODUCE INCREASINGLY STRONGER ENVIRONMENTAL VERTICAL WIND SHEAR. THE PRESENCE OF THIS VERY STRONG SHEAR WILL LIKELY CAUSE ADDITIONAL WEAKENING OF FELICIA DESPITE SLIGHTLY WARMER SSTS AND IMPROVED OCEAN HEAT CONTENT BEYOND 48 HOURS ALONG THE FORECAST TRACK. THE CURRENT INTENSITY FORECAST INDICATES THAT FELICIA WILL ONLY REMAIN TROPICAL STORM INTENSITY THROUGH 12 HOURS. BASED ON THE LATEST FORECAST FOR WEAKENING OF FELICIA TO A TROPICAL DEPRESSION LATER TODAY OR TONIGHT...TROPICAL STORMS WARNINGS WERE NOT ISSUED FOR ANY PARTS OF THE MAIN HAWAIIAN ISLANDS YET. IF THE ANTICIPATED WEAKENING TO A TROPICAL DEPRESSION DOES NOT TAKE PLACE LATER TODAY...WARNINGS MAY BE REQUIRED FOR PORTIONS OF THE AREA UNDER THE WATCH LATER TODAY. REGARDLESS OF THE INTENSITY OF FELICIA WHEN IT REACHES THE HAWAIIAN ISLANDS...LOCALLY HEAVY RAINFALL IS STILL EXPECTED TO OCCUR AND FLASH FLOODING REMAINS A POSSIBILITY. FORECAST POSITIONS AND MAX WINDS INITIAL 10/1500Z 20.5N 150.2W 40 KT 12HR VT 11/0000Z 20.3N 151.9W 35 KT 24HR VT 11/1200Z 20.3N 153.8W 30 KT 36HR VT 12/0000Z 20.4N 155.8W 30 KT 48HR VT 12/1200Z 20.5N 158.0W 30 KT 72HR VT 13/1200Z 21.4N 162.1W 25 KT...DISSIPATING 96HR VT 14/1200Z 22.5N 165.9W 20 KT...REMNANT LOW 120HR VT 15/1200Z 24.8N 169.0W 20 KT...REMNANT LOW $$ FORECASTER HOUSTON