MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (HALONG) WARNING NR 10// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 11W (HALONG), LOCATED APPROXIMATELY 122 NM NORTHWEST OF NAVSTA GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS STRONG UPPER LEVEL ANTICYCLONIC FLOW TO THE NORTH- NORTHWEST OF THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS CREATED HIGH LEVELS (30 PLUS KNOTS) OF VERTICAL WIND SHEAR (VWS). DEEP CONVECTION HAS BEEN DIMINISHING WITH A FULLY EXPOSED LLCC BECOMING VISIBLE OVER THE PAST FEW HOURS. THE CURRENT POSITIONING OF THE LLCC IS BASED ON THE EIR LOOP WITH GOOD CONFIDENCE. INTENSITY HAS BEEN DECREASED AS THE DVORAK ESTIMATES REFLECT A WEAKER SYSTEM OVER THE PAST SIX HOURS. THE TRACK HAS BEEN SHIFTED SLIGHTLY SOUTHWARD OF THE PREVIOUS FORECAST TO ACCOUNT FOR THE STEERING LEVEL CHANGE. TS 11W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 11W IS EXPECTED TO TRACK NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR THROUGH TAU 48. RECENT GUIDANCE SHOWS THE STR WILL BUILD WESTWARD AS THE MONSOON DEPRESSION (INVEST 96W) TRACKS TOWARD SOUTH KOREA. AFTER TAU 48, THE MONSOON DEPRESSION WILL BEGIN TO INTERACT WITH THE MID-LATITUDE FLOW, EVENTUALLY BEING ABSORBED WITHIN THE WESTERLY JET AND TRACKING OVER THE SEA OF JAPAN. THIS WILL CAUSE THE STR TO SHIFT, ALLOWING FOR A MORE NORTHWESTWARD TRACK PAST TAU 72. THE HIGH LEVELS OF VWS WILL PREVENT A QUICK INTENSIFICATION THROUGH TAU 48. CURRENT INDICATIONS ARE THAT AS THE SYSTEM MOVES TO THE WEST, THE UPPER LEVEL ENVIRONMENT WILL SEE MARGINAL IMPROVEMENTS, ALLOWING A DECREASE IN VWS AND A PERIOD OF QUICKER INTENSIFICATION THROUGH TAU 72. C. TS HALONG IS EXPECTED TO TRACK SLOWLY NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE STR IN THE EXTENDED TAUS. WITH THE EXCEPTION OF GFDN, COTC, AND UKMO, THE MODEL GUIDANCE SUPPORTS THE JTWC FORECAST TRACK. TS 11W IS FORECAST TO WEAKEN AS IT TRACKS INTO NORTHERLY UPPER-LEVEL FLOW AND INCREASING VWS ASSOCIATED WITH A BROAD UPPER-LEVEL HIGH TO THE NORTHWEST. DUE TO THE UNCERTAINTY IN THE TRACK SPEEDS AND INTENSITY FORECAST, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST.// NNNN NNNN