WDPS32 PGTW 041500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 16P (KEVIN) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 22.3S 173.3E INITIAL INTENSITY: 135 KTS GEOGRAPHIC REFERENCE: 394 NM SOUTHEAST OF PORT VILA, VANUATU MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 24 KTS SIGNIFICANT WAVE HEIGHT: 55 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN UNRAVELING SYSTEM WITH CONVECTIVE BANDING BECOMING FRAGMENTED BEING WRAPPED INTO THE LOW LEVEL CIRCULATION CENTER (LLCC). TC KEVIN IS IN A MARGINALLY FAVORABLE ENVIRONMENT FOR FURTHER TROPICAL ACTIVITY. THESE CONDITIONS ARE CHARACTERIZED BY CONSTANT POLEWARD OUTFLOW ALOFT, MODERATE (20-25 KTS) VERTICAL WIND SHEAR (VWS), A HEALTHY 850 MB VORTICITY SIGNATURE, OFFSET BY COOLER (24-25 C) SEA SURFACE TEMPERATURES (SST). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED EIR AND MULTI-AGENCY FIX LOCATIONS. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH MEDIUM CONFIDENCE. IT IS SET BASED OFF A BLEND OF MULTI-AGENCY AND AUTOMATED DVORAK ESTIMATES. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.5 - 127 KTS KNES: T6.5 - 127 KTS PHFO: T6.5 - 127 KTS CIMSS SATCON: 136 KTS AT 040816Z CIMSS ADT: 112 KTS AT 041330Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE VWS: 20-25 KTS SST: 24-25 CELSIUS OUTFLOW: MODERATE POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC KEVIN CONTINUES ITS SOUTHEASTWARD TRACK AS IT HUGS THE OUTER PERIPHERY OF STR TO THE EAST-NORTHEAST. BY TAU 12, TC KEVIN WILL CONTINUE TO ENTER A MORE HOSTILE ENVIRONMENT CHARACTERIZED BY STRONGER VWS AND WILL DECREASE IN INTENSITY TO 95 KNOTS AS A RESULT. BY TAU 24, TC KEVIN WILL CONTINUE ITS SUBTROPICAL TRANSITION AND WILL START TO FEEL THE EFFECTS OF DRY AIR ENTRAINMENT FROM THE NORTHWEST BEING WRAPPED INTO THE CENTER. BY TAU 36, THE SYSTEM WILL BECOME FULLY SUBTROPICAL. MODEL DISCUSSION: THE JTWC TRACK CONSENSUS MEMBERS ARE IN EXTREMELY TIGHT AGREEMENT SHOWING A CONTINUOUS SOUTHEASTWARD TRAJECTORY. THE FORECAST MODEL ENVELOPE HAS A 45 NM SPREAD BY TAU 24 WHICH PROGRESSIVELY INCREASES TO 129 NM BY TAU 36. AS A RESULT, THE JTWC FORECAST TRACK IS SET WITH HIGH CONFIDENCE. THE JTWC INTENSITY CONSENSUS MEMBERS ARE ALSO IN GOOD AGREEMENT SHOWING A DECREASING TREND AS THE SYSTEM MAKES ITS SUBTROPICAL TRANSITION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN