MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MERBOK) WARNING NR 04// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 04W (MERBOK), LOCATED APPROXIMATELY 193 NM SOUTH-SOUTHEAST OF HONG KONG, HAS TRACKED NORTH-NORTHWESTWARD AT 14 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS THE SYSTEM HAS BECOME MORE COMPACT BUT MAINTAINED CONVECTIVE DEPTH AND WRAP. THE INITIAL POSITION IS BASED ON A TIGHT CLUSTER OF WARM PIXELS IN THE CENTRAL DENSE OVERCAST WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 35 KNOTS IS BASED ON THE HIGH END OF MULTI AGENCY DVORAK ESTIMATES RANGING FROM T2.0 TO T2.5. ENVIRONMENTAL ANALYSIS INDICATES CONTINUED FAVORABLE CONDITIONS FOR DEVELOPMENT WITH LOW VERTICAL WIND SHEAR (VWS), STRONG EQUATORWARD OUTFLOW, AND VERY WARM SEA SURFACE TEMPERATURES (30-31 C). TS 04W IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THE FORECAST HAS BEEN CUT DOWN TO TAU 48 TO REFLECT DISSIPATION OVER LAND. OTHERWISE, NO OTHER SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS MERBOK IS FORECAST TO MAKE LANDFALL AFTER TAU 12 TO THE EAST OF HONG KONG AND TRACK NORTHWARD THEN NORTHEASTWARD OVER LAND AS IT ROUNDS THE WESTERN EDGE OF THE STR. FAVORABLE CONDITIONS ALONG THE FORECAST TRACK PRIOR TO LANDFALL WILL FUEL FURTHER INTENSIFICATION TO A PEAK OF 40 KNOTS. AFTERWARD, INTERACTION WITH THE RUGGED TERRAIN OF EASTERN CHINA, IN ADDITION TO INCREASED VWS WILL CAUSE RAPID EROSION AND EVENTUAL DISSIPATION BY TAU 48. REMNANTS OF TS 04W WILL EXIT INTO THE YELLOW SEA. THE DYNAMIC MODEL GUIDANCE HAS COME INTO TIGHTER AGREEMENT IN THE NEAR AND MID TERM LENDING HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN