WDPN31 PGTW 062100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 021// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 34.1N 149.3E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 479 NM EAST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL STORM (TS) 04W (MUN) WITH A SMALL PATCH OF CONVECTION OBSCURING THE EASTERN PORTION OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE LOW-LEVEL STRUCTURE REMAINS WELL-DEFINED EVEN THOUGH NORTHEASTERLY SHEAR HAS GREATLY INCREASED OVER THE PAST 6-12 HOURS. ENVIRONMENTAL ANALYSIS INDICATES THAT 04W IS NOW IN AN UNFAVORABLE ENVIRONMENT CHARACTERIZED BY WEAK EQUATORWARD OUTFLOW, HIGH (25-30 KTS) NORTHEASTERLY VERTICAL WIND SHEAR, AND BORDERLINE (25-26 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN THE ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. THE INTENSITY IS HELD SLIGHTLY HIGHER DUE TO THE INTENSITY ESTIMATES UNDERESTIMATING THE WIND SPEED IN RESPONSE TO THE DISSIPATING CONVECTION. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF BUILDING RIDGING TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T3.0 - 45 KTS KNES: T3.0 - 45 KTS CIMSS ADT: 41 KTS AT 061800Z CIMSS AIDT: 42 KTS AT 061800Z CIMSS DPRINT: 44 KTS 061800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 25-30 KTS SST: 25-26 CELSIUS OUTFLOW: WEAK EQUATORWARD OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT 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 04W IS FORECAST TO TRACK GENERALLY NORTH-NORTHWESTWARD ALONG THE WESTERN BOUNDARY OF AN EXTENSION OF RIDGING TO THE EAST THROUGH TAU 24. AFTER TAU 24, THE SYSTEM WILL ROUND THE RIDGE AXIS AND TURN TO THE NORTHEAST. SUBTROPICAL TRANSITION IS FORECAST TO BEGIN AT TAU 24 AND COMPLETE BY TAU 36 AS THE VORTEX QUICKLY BECOMES ENGULFED BY DRY AIR AND SEA SURFACE TEMPERATURES CONTINUE TO COOL. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO ONLY WORSEN OVER THE NEXT 36 HOURS, WHICH WILL CAUSE 04W TO WEAKEN THROUGHOUT THE FORECAST PERIOD. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT ON THE TRACK OF 04W WITH A 77 NM CROSS-TRACK SPREAD AT TAU 24. THERE IS SOME INCREASED ALONG-TRACK SPREAD AFTER TAU 24 DUE TO THE VORTEX BEGINNING TO INTERACT WITH THE STRONG UPPER-LEVEL WESTERLIES. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE AGREES ON WEAKENING FROM TAU 0 THROUGH TAU 36 WITH MINIMAL SPREAD BETWEEN MODELS. THEREFORE, THE JTWC INTENSITY FORECAST IS ALSO PLACED WITH HIGH CONFIDENCE, CLOSE TO CONSENSUS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: HIGH// NNNN