WDPN31 PGTW 070300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 022// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 35.0N 148.9E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 452 NM EAST OF YOKOSUKA, JAPAN MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 04W (MUN) NEARLY COMPLETELY DEVOID OF ANY DEEP CONVECTION AND SURROUNDED BY A FIELD OF DRY AIR. THE LAST BIT OF WEAK CONVECTION CAN BE SEEN BEING HEAVILY SHEARED TO THE SOUTHWEST, EXPOSING THE STILL WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). ENVIRONMENTAL ANALYSIS INDICATES THAT 04W IS IN AN UNFAVORABLE ENVIRONMENT CHARACTERIZED BY WEAK EQUATORWARD OUTFLOW ALOFT, HIGH (30-35 KTS) NORTHEASTERLY VERTICAL WIND SHEAR, SIGNIFICANT DRY AIR ENTRAINMENT, AND BORDERLINE (25-26 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LOW-LEVEL CIRCULATION IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 45 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 RCTP: T2.5 - 35 KTS CIMSS SATCON: 48 KTS AT 070000Z CIMSS ADT: 35 KTS AT 070000Z CIMSS AIDT: 42 KTS AT 070000Z CIMSS DPRINT: 33 KTS AT 070000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 30-35 KTS SST: 25-26 CELSIUS OUTFLOW: WEAK EQUATORWARD OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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 12. AFTER TAU 12, 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 ENTIRELY ENGULFED BY DRY AIR AND SEA SURFACE TEMPERATURES CONTINUE TO DROP. 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 MERE 39 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