WDPN31 PGTW 100300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING NR 022// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED APPROXIMATELY 281 NM SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHEASTWARD AT 10 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS A FULLY-EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH THE ASSOCIATED CONVECTION SHEARED TO THE NORTHEAST. A 092325Z ASCAT-A IMAGE SHOWS AN ASYMMETRIC WIND FIELD WITH A SWATH OF 50-54 KT WINDS IN THE NORTHWEST QUADRANT. BASED ON THE ASCAT IMAGE AND FULLY-EXPOSED NATURE, THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION OF TS 16W. THE INITIAL INTENSITY IS SET AT 50 KTS WITH GOOD CONFIDENCE AND IS HEDGED SLIGHTLY HIGHER THAN AN ADVANCED DVORAK TECHNIQUE ESTIMATE OF T2.7 (39 KTS) AND A 092112Z SATCON ESTIMATE OF 44 KTS BASED ON THE AFOREMENTIONED ASCAT DATA. UPPER LEVEL ANALYSIS REVEALS A ROBUST POLEWARD OUTFLOW CHANNEL ASSOCIATED WITH THE JET BEING OFFSET BY HIGH (>30 KT) VERTICAL WIND SHEAR (VWS) VALUES. SEA SURFACE TEMPERATURES (SST) REMAIN CONDUCIVE AT 26-27 CELSIUS. OVERALL, TS 16W IS TRACKING THROUGH AN UNFAVORABLE ENVIRONMENT FOR CONTINUED DEVELOPMENT AS IT TRANSITS ALONG THE NORTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTH. THE SYSTEM IS TRACKING ALONG THE BAROCLINIC ZONE AND HAS BEGUN SUBTROPICAL TRANSITION (STT) AS IT IS BEGINNING TO EXHIBIT A COMBINATION OF TROPICAL AND EXTRATROPICAL CHARACTERISTICS. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. THROUGH TAU 24, TS 16W WILL TRACK GENERALLY EASTWARD AS IT CONTINUES STT, INTERACTING WITH THE BAROCLINIC ZONE TO THE NORTH. PERSISTENT HIGH VWS WILL LEAD TO STEADY WEAKENING TO 40 KTS BY TAU 24. AFTER THIS, THE STR WILL REORIENT, CAUSING THE SYSTEM TO TURN TO A SOUTHEASTWARD TRACK AS A BREAK APPEARS WITHIN THE STR. HIGH VWS VALUES AND DRY AIR ENTRAINMENT WILL RAPIDLY WEAKEN TS 16W ALONG THIS TRACK, LEADING TO DISSIPATION BY TAU 48. THROUGHOUT THE FORECAST PERIOD, NUMERICAL MODEL GUIDANCE DIVERGES WITH GFS AND GFS ENSEMBLE SOLUTION DEPICTING THE TIGHTEST TURN TO THE SOUTH WHILE THE NAVGEM SOLUTION SHOWS THE SYSTEM TRACKING FURTHER EAST PRIOR TO TURNING SOUTHEASTWARD. NUMERICAL MODEL SPREAD AT TAU 48 IS 167 NM. DUE TO THE DIVERGENCE IN TRACK GUIDANCE, THERE IS OVERALL FAIR CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH IS PLACED NEAR THE MULTI-MODEL CONSENSUS AND THE ECMWF TRACK SOLUTION.// NNNN