WDPN31 PGTW 050300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 014// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 31.0N 146.3E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 420 NM SOUTHEAST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 04 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 04W (MUN) WITH GREATLY IMPROVED CENTRAL CONVECTION THAT IS NOW TIGHTLY WRAPPING INTO THE CENTER OF THE CIRCULATION. THE LOW-LEVEL STRUCTURE ALSO APPEARS TO HAVE IMPROVED COMPARED TO 6 HOURS AGO, AS IS EVIDENT IN THE 042246Z GMI 37 GHZ MICROWAVE IMAGE WHICH SHOWS A NEARLY COMPLETE MICROWAVE EYE FEATURE. ENVIRONMENTAL ANALYSIS INDICATES THAT 04W IS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG EASTWARD AND EQUATORWARD OUTFLOW, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (27-28 C) SEA SURFACE TEMPERATURES. THE DRY AIR THAT WAS PREVIOUSLY WITHIN THE SOUTHERN SEMICIRCLE HAS NOW MOISTENED AND IS REPLACED WITH CYCLING DEEP CONVECTION. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MENTIONED GMI MICROWAVE IMAGE AND THE ANIMATED MSI. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. THE INTENSITY IS ASSESSED TO BE HIGHER THAN WHAT MANY OF THE ESTIMATES SUGGEST DUE TO THE COMPACT NATURE OF THE CIRCULATION AND A RELATIVELY SMALL POCKET OF CONVECTION COMPARED TO AN AVERAGE SYSTEM OF THE SAME INTENSITY. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A SUBTROPICAL RIDGE TO THE SOUTH AND SOUTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS RCTP: T3.0 - 45 KTS KNES: T3.5 - 55 KTS CIMSS ADT: 34 KTS AT 050000Z CIMSS AIDT: 56 KTS AT 050000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG EQUATORWARD AND EASTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 05W IS FORECAST TO TRACK EAST-NORTHEASTWARD THROUGH TAU 24 BEFORE MAKING A TURN NORTHWARD AS RIDGING BUILDS IN TO THE EAST OF THE SYSTEM. 04W WILL THEN CONTINUE ON A GENERALLY NORTH-NORTHWESTWARD TRACK THROUGH TAU 72, ALONG THE WESTERN PERIPHERY OF THE RIDGE EXTENSION. AFTER TAU 72, THE SYSTEM IS FORECAST TO ROUND THE RIDGE AXIS AND TURN TOWARD THE NORTHEAST, WHICH WILL COMPLETE THE S-TYPE TRACK. SUBTROPICAL TRANSITION WILL BEGIN AROUND TAU 72 AND COMPLETE BY TAU 96 AS THE VORTEX SHALLOWS, BECOMES ENGULFED BY DRY AIR, AND ENTERS VERY COLD OCEAN TEMPERATURES. REGARDING INTENSITY, 04W IS FORECAST TO INTENSIFY OVER THE NEXT 24 HOURS TO A PEAK OF 65 KTS AS OUTFLOW REMAINS ROBUST AND SHEAR REMAINS LOW. AFTER TAU 24, SEA SURFACE TEMPERATURES WILL BEGIN TO DROP AND SHEAR WILL BEGIN TO RISE AS THE VORTEX GAINS LATITUDE, CAUSING A WEAKENING TREND TO PERSIST THROUGH THE REMAINDER OF THE FORECAST PERIOD. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT WITH A 180 NM CROSS-TRACK SPREAD AT TAU 72. AFTER TAU 72, ALONG-TRACK SPREAD BEGINS TO INCREASE DUE TO DIFFERING INTERACTIONS WITH THE UPPER-LEVEL ENVIRONMENT. THE JTWC TRACK FORECAST IS PLACED WITH OVERALL MEDIUM CONFIDENCE, CLOSE TO THE CONSENSUS. INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH ALL MODELS DEPICTING INTENSIFICATION THROUGH TAU 24 AND WEAKENING THEREAFTER WITHIN A TIGHT (10 KTS) ENVELOPE. AS A RESULT, THE JTWC INTENSITY FORECAST IS PLACED WITH HIGH CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: HIGH// NNNN