WDPN31 PGTW 090900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (CONSON) WARNING NR 014// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.0N 117.1E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 241 NM WEST-NORTHWEST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 14 KTS SIGNIFICANT WAVE HEIGHT: 17 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A DISORGANIZED SYSTEM WITH A LARGE FRAGMENTED BAND OF CONVECTION TO THE WEST OF THE SYSTEM CENTER. THE INITIAL POSITION IS BASED ON UPPER-LEVEL BANDING IN A 090515Z 89GHZ AMSR2 IMAGE AND THE INITIAL INTENSITY IS BASED ON THE AMSR2 WINDSPEED PRODUCT FOR THE SAME TIME SHOWING A CIRCULATION OF MOSTLY 40-45 KT WINDS WITH A PATCH OF 50 KT WINDS IN THE NORTHEAST QUADRANT. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.0 - 30 KTS KNES: T3.0 - 45 KTS CIMSS SATCON: 45 KTS AT 090453Z CIMSS ADT: 47 KTS AT 090600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: HIGH INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM (TS) 18W IS CURRENTLY TRACKING WESTWARD IN A WEAK STEERING ENVIRONMENT. AROUND TAU 48, IT WILL TURN MORE WEST-NORTHWESTWARD AS A MID-LATITUDE TROUGH BEGINS TO DEEPEN TO THE NORTH. THE SYSTEM IS EXPECTED TO MAKE LANDFALL OVER NORTHERN VIETNAM ROUGHLY 80 NM SOUTH OF HANOI. THE MARGINALLY FAVORABLE ENVIRONMENT WILL ALLOW A SLIGHT INTENSIFICATION TO A PEAK OF 70 KTS AROUND TAU 48. AFTERWARD, LAND INTERACTION WITH HAINAN AND LANDFALL OVER VIETNAM JUST BEFORE TAU 120 WILL RAPIDLY ERODE THE SYSTEM DOWN TO 25 KTS. MODEL DISCUSSION: NUMERICAL MODELS ARE IN POOR AGREEMENT, WITH AFUM AND NVGM TRACKING THE SYSTEM DIRECTLY NORTHWARD AT TAUS 12 AND 24, RESPECTIVELY. OTHER MODELS TRACK THE SYSTEM GENERALLY WESTWARD, BUT PROVIDE A WIDE RANGE OF POSSIBLE LANDFALL LOCATION. INTENSITY GUIDANCE IS IN FAIR AGREEMENT, WILL ALL MODELS SHOWING AN INTENSIFICATION PHASE PEAKING AT ABOUT 70 KTS AROUND TAU 48,FOLLOWED BY A STEADY WEAKENING TREND. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN