MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (GONI) WARNING NR 04// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 16W (GONI), LOCATED APPROXIMATELY 205 NM SOUTHEAST OF SAIPAN, HAS TRACKED WEST-NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES A CONSOLIDATING SYSTEM WITH IMPROVED DEEP CONVECTIVE BANDING OVER THE WESTERN SEMI-CIRCLE OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 141552Z NOAA-19 89 GHZ IMAGE REFLECTS THE IMPROVED CONVECTIVE ORGANIZATION AND SHOWS THAT DEEP CONVECTION HAS BUILT OVER THE LLCC, ALTHOUGH THE LLCC REMAINS POSITIONED UNDER THE EASTERN EDGE OF THE DEEP CONVECTION DUE TO LOW TO MODERATE EASTERLY VERTICAL WIND SHEAR (VWS). OVERALL, THERE IS FAIR CONFIDENCE IN THE CURRENT POSITION BASED ON RECENT EIR AND PRELIMINARY RADAR IMAGERY, WHICH GENERALLY REFLECT A WESTWARD MOTION. THE CURRENT INTENSITY IS ASSESSED AT 35 KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF T2.5 (35 KNOTS) FROM PGTW AND KNES. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (10 TO 20 KNOT) VWS BEING OFFSET BY DIVERGENT FLOW. SEA SURFACE TEMPERATURES (SSTS) ABOVE 29 CELSIUS ARE CONDUCIVE FOR FURTHER DEVELOPMENT. TS 16W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE SUB-TROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE, HOWEVER, THE FORECAST TRACK AND TRACK SPEEDS HAVE BEEN ADJUSTED SIGNIFICANTLY BASED ON THE CONTINUED WESTWARD TRACK BIAS. B. AS TS 16W STRENGTHENS, IT IS FORECAST TO GRADUALLY TURN WEST- NORTHWESTWARD OVER THE NEXT 12 HOURS AS IT TRACKS UNDER THE STEERING INFLUENCE OF THE LOW- TO MID-LEVEL STR. THE STR REMAINS ENTRENCHED TO THE NORTH BASED ON RECENT UPPER-LEVEL ANALYSES AND DYNAMIC MODEL GUIDANCE CONTINUES TO TREND ON A MORE WESTWARD TO WEST-NORTHWESTWARD TRACK, THEREFORE, THE FORECAST TRACK HAS BEEN ADJUSTED ACCORDINGLY. THERE IS STILL A FAIR AMOUNT OF UNCERTAINTY IN THE EXACT TRACK WITH A 150-NM SPREAD IN SOLUTIONS AT TAU 24, NEAR THE NORTHERN MARIANAS. TS 16W IS FORECAST TO INTENSIFY TO APPROXIMATELY 50 TO 55 KNOTS AS IT CROSSES OVER THE NORTHERN MARIANAS AND IS EXPECTED TO RAPIDLY INTENSIFY (RI) AFTER TAU 36 AND SHOULD REACH A PEAK INTENSITY NEAR 120 KNOTS. C. IN THE EXTENDED FORECAST PERIOD, TS 16W WILL TRACK ON A WEST- NORTHWESTWARD TRAJECTORY UNDER THE DOMINANT STR. FAVORABLE CONDITIONS WILL REMAIN OPTIMAL TO CONTINUE RI THROUGH TAU 96. BEYOND TAU 96, DEGRADED UPPER-LEVEL CONDITIONS AND LOWER OHC VALUES WILL BEGIN TO WEAKEN THE SYSTEM. MODEL GUIDANCE IS OVERALL IN FAIR AGREEMENT, HOWEVER, DUE TO THE COMPLEX STEERING ENVIRONMENT AND SIGNIFICANT TRACK SPEED DIFFERENCES AMONG AVAILABLE TRACKERS IN THE SHORT TERM, THE JTWC TRACK FORECAST CONFIDENCE REMAINS LOW.// NNNN NNNN