WDPN31 PGTW 151500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (KAI-TAK) WARNING NR 13// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 14W (KAI-TAK), LOCATED APPROXIMATELY 320 NM EAST-SOUTHEAST OF HONG KONG, HAS TRACKED WEST-NORTHWESTWARD AT 17 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE ORGANIZATION NEAR THE CENTER OF THE TIGHTLY WRAPPED LOW LEVEL CIRCULATION CENTER SUFFERED SOME MINOR DEGRADATION OVER THE PAST SIX HOUR AS THE SYSTEM HAS TRACKED FURTHER INTO THE SOUTH CHINA SEA. CURRENT INDICATIONS SUGGEST THE DEEP LAYERED SUBTROPICAL RIDGE (STR) HAS BEEN BUILDING MORE QUICKLY THAN PREVIOUSLY INDICATED BY MODEL GUIDANCE AND HAS LED TO A FLATTENING OF THE TRACK AND A SMALL INCREASE IN TRACK SPEED. DUE TO THE FLATTENING OF THE TRACK, THE CURRENT FORECAST HAS SHIFTED FROM SLIGHTLY EAST OF HONG KONG TO SLIGHTLY WEST OF HONG KONG. THERE HAS BEEN A NOTICEABLE FLARE OF DEEP CONVECTION WITHIN THE FEEDER BANDS LOCATED ALONG THE SOUTHERN HALF OF THE SYSTEM, AND IS BEING ADVECTED TO THE SOUTHWEST UNDER THE INFLUENCE OF MODERATE VERTICAL WIND SHEAR (VWS); HOWEVER THERE REMAINS A LACK OF CONVECTION ALONG THE NORTHERN HALF OF THE SYSTEM. THE TROPICAL UPPER TROPOSPHERIC TROUGH OVER EASTERN CHINA HAS BEEN RAPIDLY TRACKING WESTWARD AND APPEARS TO BE NO LONGER SUPPORTING ANY POLEWARD OUTFLOW. THE CURRENT INTENSITY HAS BEEN MAINTAINED AT 55 KNOTS BASED ON THE 3.5/3.5 DVORAK INTENSITY ESTIMATE FROM PGTW AND A 3.0/3.5 DVORAK FROM KNES. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 14W IS FORECAST TO MAINTAIN A WEST-NORTHWESTWARD TRACK THROUGH TAU 72 UNDER THE INFLUENCE OF THE STR. NUMERICAL MODEL GUIDANCE HAS SHOWN A SLIGHT INCREASE IN TRACK SPEED WHICH IS SUPPORTED BY THE RECENT SPEED INCREASES NOTED OVER THE PAST 12 HOURS, WITH LANDFALL EXPECTED BY 161200Z. TS 14W IS FORECAST TO INTENSIFY THROUGH LANDFALL AS THE SEA SURFACE TEMPERATURES REMAIN VERY FAVORABLE (29 TO 30 CELSIUS) WITH A NOTABLE WARM POOL LOCATED ALONG COASTAL CHINA. VWS IS EXPECTED TO REMAIN AT MODERATE LEVELS THROUGH LANDFALL, WHICH SHOULD PROVIDE THE AMPLE EQUATORWARD OUTFLOW CURRENTLY OBSERVED, BUT IS EXPECTED TO INCREASE TO HIGH LEVELS (30 KNOTS) BY TAU 36. BEYOND TAU 24, THE FRICTIONAL IMPACTS ASSOCIATED WITH LANDFALL AND INCREASING VWS WILL QUICKLY BEGIN TO DISSIPATE THE SYSTEM WITH COMPLETE DISSIPATION EXPECTED BY TAU 72. NUMERICAL MODEL GUIDANCE HAS COME INTO GOOD AGREEMENT LEADING TO HIGH CONFIDENCE IN THE TRACK FORECAST.// NNNN