MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (SARIKA) WARNING NR 10// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 24W (SARIKA), LOCATED APPROXIMATELY 245 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS SIGNIFICANT CONVECTIVE ORGANIZATION IN THE PAST SIX HOURS WITH TIGHTLY CURVED BANDING WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER (LLCC). RADAR IMAGERY FROM THE PHILIPPINES AND A 141842Z SSMI 37GHZ MICROWAVE IMAGE SHOW AN EYE JUST EAST OF PANAY ISLAND WHICH SUPPORTS THE CURRENT POSITION WITH HIGH CONFIDENCE. THE INTENSITY HAS BEEN INCREASED TO 65 KNOTS BASED ON THE IMPROVED STRUCTURE OF THE CYCLONE AND IS SUPPORTED BY A DVORAK INTENSITY ESTIMATE OF T4.0 (65 KNOTS) FROM PGTW. ENVIRONMENTAL ANALYSIS INDICATES A VERY FAVORABLE ENVIRONMENT WITH A POINT SOURCE ANTICYCLONE PROVIDING RADIAL OUTFLOW AND LOW (5-10 KNOT) VERTICAL WIND SHEAR. SEA SURFACE TEMPERATURES AND OCEAN HEAT CONTENT ARE ALSO VERY FAVORABLE. TY SARIKA HAS STARTED TO MOVE ON A MORE WEST- NORTHWESTWARD TRACK UNDER THE INFLUENCE OF A SUB-TROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TY SARIKA WILL CONTINUE TO TRACK WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STEERING STR TO THE NORTH. VERY FAVORABLE ENVIRONMENTAL CONDITIONS WILL SUPPORT INTENSIFICATION TO 90 KNOTS OVER THE NEXT 12 HOURS. EXPECT CONTINUED INTENSIFICATION PRIOR TO LANDFALL OVER LUZON IN ABOUT 20 HOURS. THERE WILL BE A SHORT WEAKENING PHASE AS THE CYCLONE TRACKS OVER THE RUGGED LUZON TERRAIN BEFORE EMERGING OVER THE SOUTH CHINA SEA (SCS) JUST BEFORE TAU 36. ENVIRONMENTAL CONDITIONS IN THE SCS WILL REMAIN FAVORABLE WHICH WILL BEGIN A SECOND INTENSIFICATION PHASE. THE STEERING STR WILL STRENGTHEN, FORCING THE CYCLONE ON A MORE WESTWARD TRACK TOWARDS HAINAN. C. IN THE EXTENDED FORECAST, TY SARIKA WILL TURN NORTHWESTWARD TOWARDS A BREAK IN THE STEERING STR. THE SYSTEM WILL SKIRT THE SOUTHERN PORTION OF HAINAN BEFORE MAKING LANDFALL NEAR HANOI, VIETNAM. THE INTENSITY IN THE EXTENDED FORECAST BECOMES MORE COMPLEX AS ENVIRONMENTAL CONDITIONS WOULD SUPPORT FURTHER INTENSIFICATION; HOWEVER, INCREASED LAND INTERACTION WITH HAINAN WILL OFFSET THE FAVORABLE ENVIRONMENT. THE INTENSITY AT LANDFALL OVER VIETNAM WILL ULTIMATELY BE TIED TO THE TRACK OF THE TYPHOON AS IT PASSES HAINAN. DYNAMIC MODEL GUIDANCE HAS BEEN FAIRLY STABLE OVER THE PAST FOUR HOURS; HOWEVER, THE GUIDANCE CONTINUES TO FAN OUT ONCE THE SYSTEM EMERGES IN THE SCS. DO TO THE MODEL SPREAD IN THE EXTENDED FORECAST, THERE REMAINS LOW CONFIDENCE IN THE FORECAST.// NNNN NNNN