WTPN31 PGTW 271500 1. TROPICAL STORM 20W (PRAPIROON) WARNING NR 007 01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 271200Z2 --- NEAR 23.1N6 128.5E6 MOVEMENT PAST SIX HOURS - 325 DEGREES AT 08 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT REPEAT POSIT: 23.1N6 128.5E6 --- FORECASTS: 12 HRS, VALID AT: 280000Z0 --- 24.5N1 126.6E5 MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT RADIUS OF 035 KT WINDS - 170 NM NORTHEAST SEMICIRCLE OVER WATER 130 NM ELSEWHERE VECTOR TO 24 HR POSIT: 305 DEG/ 11 KTS --- 24 HRS, VALID AT: 281200Z3 --- 25.8N5 124.6E3 MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT RADIUS OF 050 KT WINDS - 050 NM RADIUS OF 035 KT WINDS - 170 NM NORTHEAST SEMICIRCLE OVER WATER 130 NM ELSEWHERE VECTOR TO 36 HR POSIT: 300 DEG/ 12 KTS --- 36 HRS, VALID AT: 290000Z1 --- 27.0N9 122.3E8 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT RADIUS OF 050 KT WINDS - 060 NM RADIUS OF 035 KT WINDS - 170 NM NORTHEAST SEMICIRCLE OVER WATER 135 NM ELSEWHERE OVER WATER VECTOR TO 48 HR POSIT: 305 DEG/ 12 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 291200Z4 --- 28.4N4 120.1E4 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND RADIUS OF 050 KT WINDS - 065 NM OVER WATER RADIUS OF 035 KT WINDS - 180 NM NORTHEAST SEMICIRCLE OVER WATER 140 NM ELSEWHERE OVER WATER VECTOR TO 72 HR POSIT: 310 DEG/ 06 KTS --- 72 HRS, VALID AT: 301200Z6 --- 29.8N9 118.0E0 MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND --- REMARKS: 271500Z5 POSITION NEAR 23.4N9 128.0E1. TROPICAL STORM (TS) 20W (PRAPIROON), LOCATED APPROXIMATELY 190 NM SOUTH-SOUTHEAST OF OKINAWA HAS TRACKED NORTHWESTWARD AT 08 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 271130Z4 INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 35 KNOTS. ANIMATED SATELLITE IMAGERY SHOWS CONVECTION HAS BECOME LESS INTENSE OVER THE PAST 6 HOURS, AND THE LOW LEVEL CIRCULATION CENTER (LLCC) REMAINS DIFFICULT TO LOCATE. A RECENT, PARTIAL QUICKSCATT PASS INDICATES A VERY BROAD WIND FIELD ASSOCIATED WITH THE SYSTEM). SATELLITE IMAGERY ALSO SHOWS TS 20W STARTING TO SEPARATE FROM THE LARGE BAND OF CONVECTION EXTENDING TO THE SOUTHEAST OF THE SYSTEM. UW-CIMSS ANALYSIS INDICATES WEAK VERTICAL WIND SHEAR OVER THE AREA, WHILE THE 200 MB ANALYSIS INDICATES OUTFLOW ALOFT IS FAVORABLE. THE SYSTEM IS FORECAST TO TRACK NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE SUB-TROPICAL RIDGE TO THE NORTHEAST OF THE SYSTEM. THE SYSTEM IS FORECAST TO INTENSIFY AT A CLIMATOLOGICAL RATE UNDER A FAVORABLE UPPER LEVEL ENVIRONMENT, UNTIL MAKING LANDFALL AT APPROXIMATELY 290900Z0 200 NM SOUTH OF SHANGHAI. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 271200Z2 IS 18 FEET. REFER TO WWPW30 RJTX FOR ADDITIONAL SEA HEIGHT INFORMATION. NEXT WARNINGS AT 272100Z2 (DTG 271951Z5), 280300Z3 (DTG 280151Z7), 280900Z9 (DTG 280751Z3) AND 281500Z6 (DTG 281351Z0).//