WDPN31 PGTW 221500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W WARNING NR 10// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 04W (SONGDA), LOCATED APPROXIMATELY 190 NM NORTH-NORTHEAST OF PALAU, HAS TRACKED WEST-NORTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY AND RECENT MICROWAVE IMAGERY (221014Z TRMM AND 221102Z SSMIS) DEPICT TIGHTLY CURVED BANDING WRAPPING INTO A FORMATIVE EYE FEATURE WITH DEEP CENTRAL CONVECTION BUILDING OVER THE LOW LEVEL CIRCULATION CENTER. THERE IS FAIR CONFIDENCE IN THE CURRENT POSITION BASED ON THE FORMATIVE EYE FEATURE IN THE AFOREMENTIONED MICROWAVE IMAGERY. THE CURRENT INTENSITY IS BASED ON DVORAK INTENSITY ESTIMATES FROM KNES AND PGTW OF 55 KNOTS. UPPER LEVEL ANALYSIS INDICATES THAT THE SYSTEM REMAINS IN AN AREA OF LOW (10-15 KNOT) VERTICAL WIND SHEAR (VWS). DEVELOPMENT OF AN ANTICYCLONE DIRECTLY ABOVE THE SYSTEM IS PROVIDING STRONG DIFFLUENT FLOW ALOFT. OVER THE PAST 06 HOURS, ANIMATED WATER VAPOR IMAGERY HAS SHOWN STEADY EQUATORWARD OUTFLOW AND IMPROVED POLEWARD OUTFLOW AHEAD OF AN APPROACHING SHORTWAVE TROUGH. 3. FORECAST REASONING. A. NO CHANGE IN FORECAST PHILOSOPHY. B. TS 04W HAS TRACKED SLOWLY WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE MID-LEVEL SUBTROPICAL RIDGE (STR) AND IS FORECAST TO CONTINUE TRACKING GENERALLY WEST-NORTHWESTWARD THROUGH TAU 48. NUMERICAL MODEL GUIDANCE IS IN EXCELLENT AGREEMENT IN THE EARLY TAUS, WITH THE EXCEPTION OF GFDN, WHICH DEPICTS A SLIGHTLY MORE WESTWARD TRACK. TS SONGDA IS EXPECTED TO INTENSIFY THROUGHOUT THE FORECAST PERIOD AS IT CONTINUES TO TRACK OVER FAVORABLE SEA SURFACE TEMPERATURES AND WITHIN AN IMPROVING UPPER LEVEL ENVIRONMENT. C. IN THE EXTENDED TAUS, THE SYSTEM IS FORECAST TO TRACK NORTHWESTWARD AND THEN POLEWARD AS IT ROUNDS THE SOUTHWEST PERIPHERY OF THE STR. AN APPROACHING MID-LATITUDE TROUGH WILL WEAKEN THE WESTERN EXTENT OF THE STR AND ALLOW THE SYSTEM TO RE-CURVE AFTER THE FORECAST PERIOD. WITH THE EXCEPTION OF GFDN, WHICH TRACKS THE SYSTEM INTO NORTHERN LUZON, NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT. GFS HAS CONTINUED TO TREND SOUTHWARD BUT REMAINS THE EASTERN OUTLIER WITHIN THE AIDS ENVELOPE. THE OFFICIAL JTWC FORECAST IS CONSISTENT WITH THE PREVIOUS FORECAST AND REMAINS CLOSE TO MODEL CONSENSUS, EGRR, ECMWF, AND NOGAPS.// NNNN