WDPN31 PGTW 271500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (FOUR) WARNING NR 03// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 04W (FOUR), LOCATED APPROXIMATELY 100 NM WEST- NORTHWEST OF POHNPEI, HAS TRACKED WEST-NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY CONTINUES TO DEPICT DEEPENED CENTRAL CONVECTION WITH FORMATIVE BANDS WRAPPING INTO A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC). A 271126Z METOP-B MICROWAVE IMAGE REVEALS CONVECTIVE BANDING OVER THE NORTHERN SEMI-CIRCLE WRAPPING INTO THE LLCC. ADDITIONALLY, A 271127Z ASCAT PASS SHOWS 30 TO 35 KNOT WINDS ON THE NORTHERN SEMI-CIRCLE WITH WEAKER 20 TO 25 KNOT WINDS ON THE SOUTHERN PERIPHERY. THE CURRENT POSITION IS BASED ON THE EIR, SATELLITE FIXES FROM PGTW AND RJTD WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON AN OVERALL ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES AND THE ASCAT DATA. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM REMAINS IN AN AREA OF MODERATE (15 TO 20 KNOT) VERTICAL WIND SHEAR (VWS) BEING OFFSET BY EXCELLENT POLEWARD OUTFLOW, AS EVIDENT ON THE WATER VAPOR IMAGERY. TS 04W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF AN EXTENSIVE SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 04W WILL CONTINUE TRACKING ALONG THE SOUTHERN PERIPHERY OF THE CURRENT STEERING STR THROUGH TAU 72. STEADY INTENSIFICATION IS ANTICIPATED DUE TO STRONG DIFFLUENCE ALOFT AND PASSAGE OVER VERY WARM WATER. C. AFTER TAU 72, WEST-NORTHWESTWARD MOTION IS EXPECTED AS TS 04W IS UNDER THE STEERING INFLUENCE OF A WEAKNESS IN THE STR. STEADY INTENSIFICATION IS ALSO ANTICIPATED AS VWS DECREASES AND OTHER FAVORABLE FACTORS REMAIN IN PLACE. GIVEN THE STRAIGHTFORWARD STEERING SCENARIO AND TIGHT MODEL AGREEMENT, JTWC TRACK FORECAST CONFIDENCE LEVEL REMAINS HIGH.// NNNN