WDPN31 PGTW 111500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING NR 028// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED APPROXIMATELY 263 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED SOUTHEASTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY REVEALS AN EXPOSED, DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) WITH WEAKENING DEEP CONVECTION DISPLACED TO THE NORTHEAST. AN 111134Z MHS 89GHZ MICROWAVE IMAGE DEPICTS SHALLOW BANDING WRAPPING INTO A WEAKLY-DEFINED LLCC WITH ISOLATED, DISORGANIZED DEEP CONVECTION OVER THE EASTERN SEMICIRCLE. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON AN 111021Z ASCAT-A IMAGE SHOWING NUMEROUS 30-35 KNOT WINDS SURROUNDING A DEFINED CENTER. TS 16W IS LOCATED WITHIN A MARGINAL ENVIRONMENT AND IS TRACKING EQUATORWARD UNDER THE BACK EDGE OF AN UPPER-LEVEL SHORTWAVE TROUGH WITH STRONG (30-35 KNOTS) VERTICAL WIND SHEAR (VWS). ADDITIONALLY, THERE IS SIGNIFICANT DRY AIR ENTRAINING INTO THE SYSTEM. TS 16W APPEARS TO BE A HYBRID/SUBTROPICAL SYSTEM WITH AN ASYMMETRIC APPEARANCE IN THE TOTAL PRECIPITABLE WATER IMAGERY AND MODERATE BAROCLINICITY. THE SYSTEM IS TRACKING ALONG THE NORTHEASTERN PERIPHERY OF A LOW-LEVEL SUBTROPICAL RIDGE POSITIONED TO THE SOUTHWEST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 16W IS EXPECTED TO TURN SOUTH-SOUTHEASTWARD AS IT TRACKS ALONG THE EASTERN PERIPHERY OF THE LOW-LEVEL STR THROUGH THE FORECAST PERIOD. TS 16W WILL WEAKEN STEADILY DUE TO MODERATE TO STRONG (20-30 KT) VWS AND CONTINUED DRY AIR ENTRAINMENT WITH DISSIPATION ANTICIPATED BY TAU 36. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 36 BUT DIVERGES AFTER TAU 36. OVERALL, THERE IS FAIR CONFIDENCE IN THE JTWC FORECAST TRACK. AFTER TAU 72, AS THE SYSTEM TRACKS OVER WARM SST (28-29C) AND UNDER DECREASING VWS (<20 KNOTS), THERE IS SOME POTENTIAL FOR IT TO SLOWLY REGENERATE AS A WARM-CORE TROPICAL SYSTEM.// NNNN