WDPS31 PGTW 040300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 15P (FIFTEEN) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 21.4S 169.3E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 183 NM EAST-NORTHEAST OF NOUMEA, NEW CALEDONIA MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS PARTIALLY EXPOSED LOW-LEVEL CIRCULATION OF TROPICAL CYCLONE 15P. AS THE SYSTEM IS TRANSITING EAST-SOUTHEAST, ALL OF THE ASSOCIATED CONVECTION IS BEING HEAVILY SHEARED TO THE EAST BY THE 35-40 KTS WESTERLY VERTICAL WIND SHEAR (VWS). THE ENVIRONMENT WILL THEREFORE REMAIN MARGINALLY UNFAVORABLE, OFFSET ONLY BY WARM (27-28 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC AND THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY ESTIMATES AND OBJECTIVE AID LISTED BELOW. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE EAST-NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS CIMSS SATCON: 35 KTS AT 040030Z CIMSS ADT: 35 KTS AT 032340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE VWS: 35 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: FORECAST IS EXTENDED THROUGHOUT TAU 96 REFLECTING EXTRATROPICAL TRANSITION FORECAST DISCUSSION: TROPICAL CYCLONE 15P IS FORECAST TO CONTINUE TRACKING EAST-SOUTHEASTWARD ALONG THE PERIPHERY OF A STR TO THE NORTHEAST THROUGH TAU 48. SHORTLY AFTERWARDS, 15P WILL BEGIN TO INTERACT WITH THE BAROCLINIC ZONE, AND BY TAU 72, IT WILL START ITS EXTRATROPICAL TRANSITION, WHICH IS EXPECTED TO BE COMPLETED BY TAU 96. IN TERMS OF INTENSITY, THE SYSTEM IS EXPECTED TO BALANCE AROUND 35-40 KTS, FIGHTING OFF THE VERTICAL WIND SHEAR, WHILE UTILIZING WARM SST SUPPORT, WHICH IS FORECAST TO BE CUT OFF BY COOLER SEAS AT TAU 72. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR AGREEMENT AS FAR AS GENERAL SOUTHEASTWARD TRAJECTORY AROUND THE STR PERIPHERY, HOWEVER MODEL TRACKERS SPREAD INCREASES TO OVER 400 NM BY TAU 72. INTENSITY GUIDANCE IS IN GENERALLY FAIR AGREEMENT THROUGHOUT THE FORECAST PERIOD, INDICATING MINOR INTENSIFICATION WITHIN THE NEXT 48-72 HOURS, FOLLOWED BY STEADY WEAKENING, AS THE VERTICAL WIND SHEAR FURTHER HINDERS ANY TROPICAL DEVELOPMENT. JTWC INTENSITY FORECAST IS HEDGED ON THE HIGHER SIDE OF THE MULTI-MODEL CONSENSUS, CONSIDERING IMPACTS FROM COAMPS-TC AND HAFS GUIDANCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN