WDPN32 PGTW 140300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (RAMMASUN) WARNING NR 15// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 09W (RAMMASUN), LOCATED APPROXIMATELY 583 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE DEEP CENTRALIZED CONVECTION HAS PERSISTED OVER THE PAST FEW HOURS WITH INCREASING OUTFLOW TO THE SOUTHWESTERN QUADRANT. THE CURRENT INTENSITY HAS BEEN INCREASED TO 50 KNOTS BASED ON THE BETTER OBSERVED ORGANIZATION IN MSI WITH DVORAK ESTIMATES FROM PGTW AND RJTD INCREASING IN THE PAST SIX HOURS. TS 09W HAS SLOWED SLIGHTLY AS THE SYSTEM HAS STARTED TO DEVELOP VERTICALLY WITH DECREASING VERTICAL WIND SHEAR (VWS) (5 TO 10 KNOTS). TS 09W REMAINS ON A WESTWARD TRACK ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) ANCHORED TO THE NORTH OF THE SYSTEM. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 09W IS FORECAST TO CONTINUE WESTWARD FOR THE NEXT 36 HOURS ALONG THE SOUTHERN PERIPHERY OF THE ENTRENCHED STR. IMPROVING UPPER LEVEL SUPPORT AND FAVORABLE SEA SURFACE TEMPERATURES (SST) WILL PROVIDE FOR FURTHER INTENSIFICATION THROUGH LANDFALL INTO THE CENTRAL PHILIPPINES SLIGHTLY AFTER TAU 24. AS THE SYSTEM TRACKS OVER LAND, A SLIGHT WEAKENING TREND IS ANTICIPATED THROUGH TAU 48. AS THE CIRCU- LATION CROSSES OVER SOUTHERN LUZON INTO THE SOUTH CHINA SEA, AN IMPROVING ENVIRONMENT IN THE LOW LEVEL FLOW, WITH IMPROVING UPPER LEVEL SUPPORT WILL CAUSE TS 09W TO START INTENSIFYING BY TAU 72. THE TRACK WILL SHIFT TO A MORE WEST-NORTHWESTWARD DIRECTION AS THE STR WEAKENS SLIGHTLY UNDER THE INFLUENCE OF A DIGGING MID-LATITUDE TROUGH OVER EASTERN CHINA. C. IN THE EXTENDED TAUS, TS RAMMASUN IS FORECAST TO TRACK WEST- NORTHWESTWARD ACROSS THE SOUTH CHINA SEA TOWARDS NORTHERN HAINAN ISLAND, MAKING LANDFALL AROUND TAU 108 INTO THE LUICHOW PENINSULA. WARM SSTS, DECREASED VWS, AND INCREASED OUTFLOW IN THE SOUTH CHINA SEA WILL ALLOW FOR INTENSIFICATION, REACHING A MAXIMUM OF 85 KNOTS PRIOR TO LANDFALL. MODEL GUIDANCE IS IN GOOD AGREEMENT WITH SOME DIFFERENCES IN TRACK SPEED BUT IS OTHERWISE TIGHTLY GROUPED. DUE TO THE LOW CONFIDENCE IN THE INITIAL POSITION AND THE UNCERTAINTY IN THE TRANSLATIONAL SPEED, THE CONFIDENCE IN THE FORECAST REMAINS LOW.// NNNN