MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (WIPHA) WARNING NR 06// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 08W (WIPHA), LOCATED APPROXIMATELY 281 NM EAST OF HANOI, VIETNAM, HAS TRACKED NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED IMAGERY SHOWS A LARGE AREA OF FRAGMENTED, FLARING, AND POORLY ORGANIZED DEEP CONVECTION WITH MONSOON DEPRESSION CHARACTERISTICS. THE MAIN BANDS ARE FEEDING IN FROM THE SOUTH INTO A BROAD, ELONGATED AND ASYMMETRICAL LOW LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS FROM AN LLC FEATURE IN THE 312212Z SSMIS IMAGE AND TRIANGULATED FROM MULTIPLE SURFACE OBSERVATIONS INCLUDING HAIKOU, HAINAN. THE INITIAL INTENSITY OF 30 KNOTS IS AVERAGED FROM AGENCY DVORAK ESTIMATES AND SUPPORTED BY NEARBY SURFACE OBSERVATIONS. UPPER LEVEL ANALYSIS INDICATES AN EASTWARD OUTFLOW CHANNEL TOWARD A TUTT CELL ANCHORED OVER OKINAWA THAT IS PROVIDING VENTILATION TO THE FLARING CONVECTION. HOWEVER, THIS IS OFFSET BY A MODERATE (15-20 KNOT) EASTERLY VERTICAL WIND SHEAR (VWS). TD 08W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 08W IS EXPECTED TO REMAIN ON ITS CURRENT TRACK THROUGHOUT THE FORECAST, MAKING LANDFALL OVER THE LEIZHOU PENINSULA SHORTLY AFTER TAU 06. AFTERWARD, IT WILL CROSS THE GULF OF TONKIN MOMENTARILY BEFORE MAKING A FINAL LANDFALL IN SOUTH CHINA NEAR BEIHAI. LAND INTERACTION, IN ADDITION TO THE MODERATE VWS, OFFSET BY THE MOMENTARY DRIFT OVER WATER, WILL GRADUALLY ERODE THE SYSTEM, LEADING TO DISSIPATION BY TAU 36. AVAILABLE NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH NAVGEM AS THE LEFT OF TRACK OUTLIER. THERE IS A SMALL PROBABILITY THAT TD 08W WILL TRACK MORE WESTWARD, AS PROPOSED BY NAVGEM, RESULTING IN A LONGER DRIFT OVER THE GULF OF TONKIN, HENCE, A LONGER LIFESPAN. THERE IS OVERALL FAIR CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID CLOSE TO CONSENSUS.// NNNN NNNN