WDPN31 PGTW 090300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (CONSON) WARNING NR 013// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.8N 118.3E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 172 NM WEST-NORTHWEST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A DISORGANIZED SYSTEM WITH FRAGMENTED FEEDER BANDS THAT IS STRUGGLING TO CONSOLIDATE AFTER IT CROSSED THE PHILIPPINE ARCHIPELAGO AND EXITED INTO THE SOUTH CHINA SEA. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE USING LOW CLOUD TRACING IN THE MSI LOOP AND LINED UP WITH A WEAK LOW LEVEL NOTCH FEATURE IN THE 082256Z AMSU-B MICROWAVE IMAGE. THE INITIAL INTENSITY IS ASSIGNED WITH MEDIUM CONFIDENCE BASED ON THE HIGH END OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SUSTAINED 6-HR CONVECTIVE SIGNATURE. ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH LOW VWS AND WARM SSTS OFFSET BY WEAK UPPER LEVEL OUTFLOW. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE NORTHEAST. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 51 KTS AT 082257Z CIMSS ADT: 45 KTS AT 082340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM 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: TS CONSON WILL CONTINUE ON ITS CURRENT TRACK UP TO TAU 36; AFTERWARD, IT WILL TURN MORE WEST-NORTHWESTWARD AS THE STR IS WEAKENED BY A MID-LATITUDE TROUGH, PASS TO THE SOUTH OF HAINAN INTO THE GULF OF TONKIN, AND BY TAU 120, WILL MAKE LANDFALL OVER NORTHERN VIETNAM JUST SOUTH OF HANOI. THE MARGINALLY FAVORABLE ENVIRONMENT WILL FUEL A SLOW INTENSIFICATION TO A PEAK OF 70KTS AT TAUS 48-72. AFTERWARD, LAND INTERACTION WITH HAINAN AND LANDFALL OVER VIETNAM WILL RAPIDLY ERODE THE SYSTEM DOWN TO 35KTS. MODEL DISCUSSION: NUMERICAL MODELS ARE IN POOR AGREEMENT, SIGNIFICANTLY SPREADING TO 810NM BY TAU 120 WITH NAVGEM THE EXTREME OUTLIER ON THE RIGHT, DRASTICALLY DEFLECTING THE VORTEX NORTHWARD AFTER TAU 36, A POSSIBLE EXCESSIVE BINARY INTERACTION WITH A SECONDARY CYCLONE (STY 19W IN THE PHILIPPINE SEA). IN VIEW OF THESE, THERE IS LOW CONFIDENCE IN THE FULL EXTENT OF THE JTWC TRACK FORECAST. THERE IS MEDIUM CONFIDENCE IN THE INTENSITY FORECAST UP TO TAU 72 AND LOW CONFIDENCE AFTERWARD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN