WDPN32 PGTW 311500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (MIRINAE) WARNING NR 23// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 23W (MIRINAE)HAS CONTINUED TO MOVE WESTWARD UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO THE NORTH. THE SYSTEM HAS BEEN SLOW TO REACQUIRE DEEP CONVECTION, DESPITE INDICATIONS FROM 311058Z QUIKSCAT IMAGE THAT A WELL-DEFINED LOW LEVEL CIRCULATION CENTER OF AT LEAST 50 KNOTS REMAINS. CURRENT DVORAK INTENSITY ESTIMATES FROM PGTW, KNES, AND RJTD ALSO SUPPORT A 45 TO 55 KNOT SYSTEM. UPPER AIR SOUNDINGS ALONG SOUTHERN CHINA INDICATE THE MID TO UPPER LEVELS OF THE ATMOSPHERE HAVE BECOME INCREASINGLY LESS SATURATED, WHICH MAY BE INHIBITING THE DEVELOPMENT OF CONVECTIVE CLOUDS. 3. FORECAST REASONING. A. THE FORECAST REASONING HAS NOT CHANGED SIGNIFICANTLY SINCE THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TS 23W WILL CONTINUE TO TRACK ALMOST DUE WESTWARD THROUGHOUT THE FORECAST PERIOD AS IT TRACKS ALONG THE SOUTHERN PERIPHERY OF THE MID- LEVEL SUBTROPICAL RIDGE TO THE NORTH. A DEVELOPING COLD SURGE ASSOCIATED WITH A STRENGTHENING RIDGE CENTER OVER INTERIOR ASIA WILL INITIATE GRADUAL WEAKENING. BY TAU 24 (AS THE COLD SURGE STRENGTHENS), THE STORM WILL SIT IN LOWER OCEANIC HEAT, UNDER INCREASED VERTICAL WIND SHEAR, AND WITHIN A RELATIVELY MORE STABLE ENVIRONMENT. ALL OF THESE FACTORS WILL PROMOTE FURTHER DEGRADATION OF THE VERTICAL STRUCTURE OF THE STORM. THE STORM WILL BOTH WEAKEN AND DEFLECT SLIGHTLY SOUTH OF WEST DUE TO THE NORTHERLY FLOW ASSOCIATED WITH THE SURGE. THE STORM IS EXPECTED TO DISSIPATE OVER EASTERN CAMBODIA BY TAU 48.// NNNN