MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 30W (HAIKUI) WARNING NR 04// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 30W (HAIKUI), LOCATED APPROXIMATELY 44 NM WEST-SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WEST- NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A SYSTEM THAT HAS HELD TOGETHER WELL OVER THE LAST SIX HOURS AS IT TRACKED ACROSS THE PHILIPPINES AND JUST NOW EMERGING OVER THE SOUTH CHINA SEA. SATELLITE IMAGERY ALSO DEPICTS FORMATIVE BANDING OF DEEP CONVECTION WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER (LLCC) BUT CLOUD TOPS ARE BEGINNING TO WARM SLIGHTLY. ANIMATED RADAR IMAGERY FROM PAGASA SHOWS MODERATE PRECIPITATION WITH GENERAL ROTATION AROUND THE LLCC, AND COMBINED WITH SATELLITE FIXES IS THE BASIS FOR THE INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 30 KNOTS AND IS BASED SUBJECTIVE DVORAK ESTIMATES FROM ALL AGENCIES REPORTING T2.0 (30 KNOTS). UPPER-LEVEL ANALYSIS SHOWS A FAVORABLE TO MARGINAL ENVIRONMENT WITH LOW VERTICAL WIND SHEAR, SIGNIFICANT DIFFLUENCE ON THE WESTERN PERIPHERY WITH A PRONOUNCED POLEWARD OUTFLOW CHANNEL TAPING INTO THE MIDLATITUDE WESTERLY JET, AND VERY WARM (30 CELSIUS) SSTS. CONDITIONS HAVE DETERIORATED SLIGHTLY AS THE UPPER-LEVEL POINT SOURCE PREVIOUSLY LOCATED OVER THE SYSTEM CENTER IS NOW DISPLACED NORTHEAST OF THE LLCC, OVER THE PHILIPPINE SEA, AND BEGINNING TO RESTRICT OUTFLOW ON THE EASTERN PERIPHERY. CURRENTLY TD 30W IS TRACKING WEST-NORTHWEST ALONG THE SOUTHERN BOUNDARY OF A DEEP- LAYERED SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH. A. THE FORECAST PHILOSOPHY HAS CHANGED TO REFLECT A WEST- SOUTHWEST FORECAST TRACK IN THE EXTENDED TAUS. B. TD 30W WILL CONTINUE TRACKING NORTHWESTWARD OVER THE NEXT 48 HOURS ALONG THE CURRENT STEERING RIDGE. ENVIRONMENTAL CONDITIONS ARE FORECAST TO REMAIN OVERALL FAVORABLE WITH A PERSISTENT POLEWARD OUTFLOW CHANNEL FEEDING INTO THE WESTERLY JET, ACCOMPANIED BY VERY WARM SSTS. THE UPPER-LEVEL ANTICYCLONE WILL REMAIN WELL EAST OF TD 30W LIMITING OUTFLOW ON THE EASTERN EDGE, BUT NOT ENOUGH TO STIFLE DEVELOPMENT. TD 30W IS FORECAST TO INTENSIFY INTO A SMALL AND FAIRLY COMPACT TYPHOON BY TAU 48, BUT THE SYSTEM WILL TRACK INTO COOLER WATERS AND ENCOUNTER INCREASING WIND SHEAR MITIGATING FURTHER DEVELOPMENT BEYOND TAU 48. SHORTLY THEREAFTER, TD 30W TRACK WILL BEGIN TO SLOW AS IT ENCOUNTERS A DEVELOPING RIDGE TO THE WEST SHIFTING THE TRACK WESTWARD TO WEST-SOUTHWESTWARD. C. IN THE EXTENDED PERIOD, STEERING WILL TRANSITION FROM THE NORTHEAST STR TO THE DEVELOPING NORTHWEST STR, SHIFTING THE TRACK SOUTHWESTWARD. THIS MARKS A SIGNIFICANT CHANGE FROM THE PREVIOUS FORECAST PHILOSOPHY WHICH FAVORED A WEAKENING NORTHEAST STR AND A RECURVE SCENARIO. ENVIRONMENTAL CONDITIONS WILL GRADUALLY DETERIORATE RESULTING IN A SIMILAR WEAKENING TREND. DYNAMIC MODEL GUIDANCE SHOWS GENERALLY GOOD AGREEMENT WITH THE NEW FORECAST PHILOSOPHY WITH ONLY COAMPS STILL FAVORING THE RECURVE SCENARIO. SOME UNCERTAINTY STILL EXISTS IN THE LATER TAUS AS STEERING TRANSITIONS TO THE WESTERN RIDGE, WHICH LENDS OVERALL LOW CONFIDENCE IN THE FORECAST TRACK.// NNNN NNNN