MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (SINLAKU) WARNING NR 004// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 04W (SINLAKU), LOCATED APPROXIMATELY 121 NM SOUTH OF HANOI, VIETNAM, HAS TRACKED WESTWARD AT 07 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A BROAD LOW LEVEL CIRCULATION CENTER (LLCC) WITH FRAGMENTED DEEP CONVECTIVE BANDING OVER THE WESTERN SEMICIRCLE. BASED ON THE MSI AND AN EXTRAPOLATION OF A 012036Z GMI 89 GHZ MICROWAVE IMAGE SHOWING A BROAD LLCC, THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS SET AT 35 KTS, SLIGHTLY HIGHER THAN A DVORAK CURRENT INTENSITY ESTIMATE OF T2.0 (30 KTS) BY RJTD AND LOWER THAN A SUBJECTIVE DVORAK INTENSITY ESTIMATE OF T2.9 (43 KTS). THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE WITH HIGH (>25 KTS) NORTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSETTING THE WARM (>30 CELSIUS) SEA SURFACE TEMPERATURES AND GOOD UPPER LEVEL OUTFLOW. TS 04W IS CURRENTLY TRACKING WESTWARD ALONG THE PERIPHERY OF THE LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE IN FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 04W IS EXPECTED TO TRACK WEST-NORTHWESTWARD THROUGHOUT THE FORECAST PERIOD, MAKING LANDFALL OVER VIETNAM PRIOR TO TAU 12. AS THE SYSTEM TRANSITS OVER THE WARM WATERS OF THE GULF OF TONKIN, TS 04W IS FORECAST TO WEAKEN DUE TO THE PERSISTENT NORTHEASTERLY VWS (25-30 KTS) AND LAND INTERACTION. UPON LANDFALL, THE SYSTEM WILL STEADILY WEAKEN AS IT TRACKS INLAND OVER MOUNTAINOUS TERRAIN. DISSIPATION IS ANTICIPATED BY TAU 36, IF NOT SOONER. THERE IS GOOD CONFIDENCE IN THE JTWC TRACK FORECAST WHICH IS PLACED NEAR THE MULTI-MODEL CONSENSUS.// NNNN NNNN