WDPN31 PGTW 241500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (SAUDEL) WARNING NR 023// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 19W (SAUDEL), LOCATED APPROXIMATELY 207 NM EAST-NORTHEAST OF DA NANG, VIETNAM, HAS TRACKED WESTWARD AT 10 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY REVEALS DEEP FLARING CONVECTION OVERHEAD THE LOW LEVEL CIRCULATION CENTER (LLCC). A BULLSEYE 241229Z ASCAT-A DEPICTS A SMALL SWATH OF 45-50 KTS WIND BARBS TO THE SOUTHEAST OF A SYMMETRIC LLCC AND WEAKER WINDS ELSEWHERE, LENDING GOOD CONFIDENCE TO THE INITIAL POSITION AND INTENSITY. THE INITIAL INTENSITY REMAINS AT 50 KTS, HEDGED SLIGHTLY UNDER MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T3.5 (55 KTS) BASED ON THE ASCAT DATA. ENVIRONMENTAL ANALYSIS SHOWS MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS), GOOD EQUATORWARD OUTFLOW AND WARM (27-28 CELSIUS) SEA SURFACE TEMPERATURES (SST) CONTRIBUTING TO AN OVERALL MARGINAL ENVIRONMENT. TS 19W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. UNDER THE STEERING INFLUENCE OF THE AFOREMENTIONED RIDGE, TS 19W WILL CONTINUE TO MOVE STEADILY WESTWARD THEN WEST-SOUTHWESTWARD THROUGHOUT THE FORECAST PERIOD. INCREASING VWS WILL CAUSE THE SYSTEM TO SLOWLY WEAKEN AS IT APPROACHES VIETNAM WITH LANDFALL ANTICIPATED PRIOR TO TAU 36. AFTERWARDS, THE SYSTEM WILL RAPIDLY WEAKEN AS IT TRANSITS ACROSS THE RUGGED TERRAIN WITH DISSIPATION EXPECTED BY TAU 48. NUMERICAL MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT WITH A SPREAD OF ONLY 54 NM PRIOR TO LANDFALL. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK WHICH LIES NEAR THE MULTI- MODEL CONSENSUS.// NNNN