MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (WIPHA) WARNING NR 10// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 08W (WIPHA), LOCATED APPROXIMATELY 185 NM EAST OF HANOI, VIETNAM, HAS TRACKED SOUTHWESTWARD AT 01 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY CONTINUES TO SHOW A RELATIVELY UNIMPRESSIVE AND RAGGED SYSTEM WITH SOME INCREASED DEEP CONVECTION BEGINNING TO DEVELOP NEAR THE ASSESSED LOW LEVEL CENTER AS INDICATED BY OVERSHOOTING TOPS EVIDENT IN THE EARLY MORNING MULTISPECTRAL IMAGERY. WHILE NOT EVIDENT IN THE MULTISPECTRAL IMAGERY, LAND BASED RADAR COMPOSITES FROM CHINA INDICATE A VERY WELL-DEFINED EYE FEATURE ASSOCIATED WITH THIS SYSTEM, JUST OFFSHORE BEHAI, CHINA. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE RADAR LOOP AND NEARBY SURFACE OBSERVATIONS, INCLUDING THOSE FROM BEHAI. A 012318Z SSMIS 89 GHZ MICROWAVE IMAGE WITH A WEAK MICROWAVE EYE FEATURE LENDS SUPPORT TO THE INITIAL POSITION AND SHOWS A BROAD BAND OF DEEP CONVECTION OVER WATER TO THE SOUTH OF THE LLCC. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (15-20 KNOTS) VWS AND STRONG EQUATORWARD OUTFLOW. A WEAK POINT SOURCE APPEARS TO HAVE DEVELOPED OVER THE TOP OF TS 08W, WHICH IS PROVIDING SOME ADDITIONAL POLEWARD OUTFLOW ALONG THE WESTERN SIDE OF AN UPPER-LEVEL ANTICYCLONE TO THE EAST NEAR HONG KONG. SSTS IN THE AREA OF 30-31 DEGREES CELSIUS ARE SUPPORTIVE FOR INTENSIFICATION. AFTER REEMERGING INTO THE GULF OF TONKIN, FORWARD MOTION HAS SLOWED CONSIDERABLY, WITH THE SYSTEM NOW BECOMING QUASI-STATIONARY WHILE MOVING THROUGH A GENERALLY WEAK STEERING ENVIRONMENT BETWEEN A STR OVER EAST-CENTRAL CHINA AND NER CENTERED NEAR THE NORTHERN STRAIT OF MALACCA. 3. FORECAST REASONING. A. WHILE THE OVERALL FORECAST PHILOSOPHY HAS NOT CHANGED, DUE TO THE QUASI-STATIONARY MOTION IN THE NEAR-TERM, THE TRACK HAS BEEN ADJUSTED TO REMAIN OVER WATER THROUGH TAU 48 AND THE FORECAST EXTENDED TO TAU 72. B. OVER THE NEXT 24 HOURS, TS 08W WILL DRIFT SLOWLY SOUTHWESTWARD UNDER THE INFLUENCE OF A WEAK STEERING ENVIRONMENT. BY TAU 24, AN UPPER-LEVEL ANTICYCLONE WILL STRENGTHEN OVER SOUTHERN CHINA, ALLOWING TS 08W TO ACCELERATE SLIGHTLY WHILE MAINTAINING AND OVERALL SOUTHWESTWARD TRACK THROUGH TAU 48, PARALLEL TO THE VIETNAMESE COASTLINE. THE SYSTEM IS FORECAST TO MAKE LANDFALL SOUTH OF HANOI NEAR TAU 60. THE SYSTEM IS FORECAST TO INTENSIFY SLIGHTLY AS IT REMAINS OVER VERY WARM (30-31 DEGREES CELSIUS) AND MAINTAINS ROBUST EQUATORWARD AND WEAK POLEWARD OUTFLOW THROUGH TAU 24 WITH RELATIVELY LOW VWS. THEREAFTER THE SYSTEM WILL GRADUALLY WEAKEN, AS THE OUTFLOW GRADUALLY BECOMES LESS DIFFLUENT AND VWS INCREASES. DYNAMIC MODEL GUIDANCE IS IN MODERATE AGREEMENT ON THE TRACK OF TS 08W, WITH THE ECMWF SOLUTION TAKING THE SYSTEM INLAND MUCH SOONER AND CLOSER TO HANOI, WHILE THE AFUM AND NAVGEM KEEP THE SYSTEM OVER WATER AND FURTHER SOUTH. THE OFFICIAL JTWC FORECAST TRACK LIES JUST SOUTH OF THE MULTI-MODEL CONSENSUS, BUT IS MUCH SLOWER IN LIGHT OF THE NEAR- TERM QUASI-STATIONARY MOTION, LEADING TO A LONGER PERIOD OVER WATER IN WHICH THE SYSTEM COULD INTENSIFY. DUE TO THIS UNCERTAINTY, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN