WDPN32 PGTW 102100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 19W (CHANTHU) WARNING NR 019// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.5N 122.3E INITIAL INTENSITY: 155 KTS GEOGRAPHIC REFERENCE: 518 NM SOUTHWEST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 55 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: DESPITE UNDERGOING AN EYEWALL REPLACEMENT CYCLE (ERC), STY 19W HAS INTENSIFIED OVER THE PAST 12 HOURS WITH A STEADY INCREASE IN INTENSITY FROM 145 KNOTS AT 100600Z TO 155 KNOTS AT 101800Z. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY NEAR WARNING TIME (101800Z) DEPICTS A 14NM ROUND EYE WITH EYE TEMPERATURES RANGING FROM 11-14C (WMG) SURROUNDED BY CMG, WHICH YIELDS A DT7.5 (155 KNOTS). SINCE THAT TIME, EIR IMAGERY INDICATES COOLING EYE TEMPERATURES AND RADAR IMAGERY REVEALS A BREAK IN THE EYEWALL OVER THE NORTHWEST QUADRANT (UW-CIMSS ADT RAW T-NUMBER ESTIMATE HAS ALSO DECREASED TO 6.7). THIS SUGGESTS ERC AS INDICATED IN THE UW-CIMSS M-PERC PRODUCT BUT IT'S DIFFICULT TO VERIFY DUE TO THE SPARSITY OF HIGH-RESOLUTION MICROWAVE IMAGERY. UPPER-LEVEL CONDITIONS HAVE REMAINED HIGHLY FAVORABLE WITH STRONG RADIAL OUTFLOW AND ENHANCED POLEWARD OUTFLOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: DEEP-LAYERED, NORTH-SOUTH ORIENTED SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST AND NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T7.5 - 155 KTS RJTD: T7.5 - 155 KTS RCTP: T7.5 - 155 KTS KNES: T7.0 - 140 KTS CIMSS SATCON: 146 KTS AT 101403Z CIMSS ADT: 152 KTS AT 101730Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: ADJUSTED 101200Z INTENSITY TO 150 KNOTS AND INCREASED THE 101800Z INITIAL INTENSITY TO 155 KNOTS BASED ON THE RECENT INTENSIFICATION TREND REFLECTED IN DVORAK AND ADT ESTIMATES. FORECAST DISCUSSION: AS STY 19W TRACKS AWAY FROM NORTHERN LUZON AND COMPLETES ERC, THE CONVECTIVE STRUCTURE WILL LIKELY IMPROVE AGAIN THUS THE FORECAST IS MAINTAINED AT STY STRENGTH THROUGH TAU 12. AFTER TAU 12, STY 19W WILL TRACK POLEWARD ALONG THE WESTERN PERIPHERY OF THE STR AND WILL STEADILY WEAKEN AS IT INTERACTS WITH TAIWAN. AFTER TAU 48, THE SYSTEM WILL INTERACT WITH AN UPPER-LEVEL SUBTROPICAL TROUGH AND STEADILY WEAKEN AS IT BECOMES EMBEDDED WITHIN THE TROUGH WITH CONVERGENT UPPER-LEVEL FLOW AND UNFAVORABLE LEVELS OF MID-LEVEL VERTICAL WIND SHEAR. IN THE EXTENDED PERIOD, STY 19W IS FORECAST TO TRACK SLOWLY EASTWARD WITHIN WEAK WESTERLY FLOW AND WILL WEAKEN TO TS STRENGTH (50-55 KNOTS) BY TAU 120. GLOBAL MODEL GUIDANCE INDICATES A FAIRLY ATYPICAL MIDLATITUDE PATTERN WITH WEAK SUBTROPICAL WESTERLIES AND THE FRONTAL ZONE TO THE NORTH OVER THE KOREAN PENINSULA, THEREFORE, EXTRATROPICAL TRANSITION IS NOT LIKELY. ADDITIONALLY, TRACK SPEEDS SHOULD BE UNUSUALLY SLOW. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72 WITH A 125NM SPREAD IN SOLUTIONS AT TAU 72 LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK. AFTER TAU 72, THERE IS INCREASING UNCERTAINTY WITH WEAKER STEERING FLOW THUS MEDIUM TRACK CONFIDENCE. OVERALL, THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST DUE TO THE COMPLEX INTERACTIONS WITH THE AFOREMENTIONED TROUGH AND SUBTROPICAL WESTERLIES AS WELL AS INTERACTION WITH TAIWAN AND EASTERN CHINA. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN