WDPN31 PGTW 040300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (SONAMU) WARNING NR 03// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 01W (SONAMU), LOCATED APPROXIMATELY 595 NM EAST-SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY INDICATES THAT SYSTEM HAS CONTINUED TO CONSOLIDATE OVER THE PAST SIX HOURS WITH A CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). CONSEQUENTLY, DVORAK INTENSITY ESTIMATES HAVE INCREASED TO 35 KNOTS AND THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS. THE IMPROVED ORGANIZATION IS EVIDENT IN A 032207Z CORIOLIS 37 GHZ IMAGE, WHICH SHOWS TIGHTLY-CURVED CONVECTIVE BANDING WRAPPING INTO A WELL-DEFINED CENTER LOCATED JUST WEST OF THE SOUTHERN TIP OF PALAWAN ISLAND, THEREFORE, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. TD 01W IS SITUATED WITHIN A MARGINAL UPPER- LEVEL ENVIRONMENT WITH MODERATE TO STRONG (20 TO 30 KNOTS) EASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY STRONG DIFFLUENCE AND GOOD POLEWARD OUTFLOW INTO THE UPPER-LEVEL WESTERLIES. TD O1W IS CURRENTLY TRACKING WESTWARD UNDER THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) THAT IS ENTRENCHED OVER THE WESTERN PACIFIC AND SOUTH CHINA SEA. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 01W WILL CONTINUE TO TRACK WESTWARD THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE LOW- TO MID-LEVEL STR POSITIONED OVER THE NORTHERN SOUTH CHINA SEA. DYNAMIC MODEL GUIDANCE IS IN FAIR AGREEMENT WITH SOLUTIONS VARYING FROM A WESTWARD TRACK TO A WEST- SOUTHWESTWARD TRACK. THE DIFFERENCES ARE LIKELY DUE TO HOW THE MODELS ARE HANDLING THE INTERACTION WITH THE NORTHEAST SURGE FLOW. THE JTWC FORECAST IS POSITIONED CLOSE TO THE MODEL CONSENSUS, FAVORING THE ECMWF AND GFS SOLUTIONS. TD 01W IS FORECAST TO INTENSIFY TO A PEAK OF 45 KNOTS BY TAU 24. AFTER TAU 24, TD 01W IS EXPECTED TO ENCOUNTER INCREASING VWS ASSOCIATED WITH A RENEWED NORTHEAST SURGE, WHICH WILL SERVE TO WEAKEN THE SYSTEM. C. IN THE EXTENDED TAUS, TD 01W IS FORECAST TO DISSIPATE AND TURN SOUTHWESTWARD AS IT TRANSITIONS TO THE STEERING INFLUENCE OF THE NEAR-EQUATORIAL RIDGE FORECAST TO STRENGTHEN TO THE SOUTHWEST OVER INDONESIA. THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK THROUGH TAU 72. IN THE EXTENDED TAUS, DUE TO UNCERTAINTIES IN THE INTENSITY FORECAST AND DIFFERENCES IN THE MODEL TRACK SOLUTIONS, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN