WTPN31 PGTW 310900 AMD 1. TYPHOON 20W (PRAPIROON) WARNING NR 022A AMENDED 02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE --- WARNING POSITION: 310600Z0 --- NEAR 35.2N0 124.0E7 MOVEMENT PAST SIX HOURS - 005 DEGREES AT 20 KTS POSITION ACCURATE TO WITHIN 030 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT RADIUS OF 050 KT WINDS - 085 NM EAST SEMICIRCLE 055 NM ELSEWHERE RADIUS OF 035 KT WINDS - 160 NM EAST SEMICIRCLE OVER WATER 115 NM ELSEWHERE REPEAT POSIT: 35.2N0 124.0E7 --- FORECASTS: 12 HRS, VALID AT: 311800Z3 --- 38.8N9 126.4E3 MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND RADIUS OF 050 KT WINDS - 065 NM SOUTHEAST SEMICIRCLE OVER WATER 050 NM ELSEWHERE OVER WATER RADIUS OF 035 KT WINDS - 135 NM SOUTHEAST SEMICIRCLE OVER WATER 105 NM ELSEWHERE OVER WATER VECTOR TO 24 HR POSIT: 040 DEG/ 16 KTS --- 24 HRS, VALID AT: 010600Z7 --- 41.2N7 129.0E2 MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 035 KT WINDS - 120 NM SOUTHEAST SEMICIRCLE OVER WATER 080 NM ELSEWHERE OVER WATER VECTOR TO 36 HR POSIT: 065 DEG/ 13 KTS --- 36 HRS, VALID AT: 011800Z0 --- 42.3N9 132.2E8 MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT BECOMING EXTRATROPICAL RADIUS OF 035 KT WINDS - 085 NM SOUTHEAST SEMICIRCLE OVER WATER 065 NM ELSEWHERE OVER WATER VECTOR TO 48 HR POSIT: 065 DEG/ 13 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 020600Z8 --- 43.4N1 135.4E3 MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT BECOMING EXTRATROPICAL VECTOR TO 72 HR POSIT: 070 DEG/ 11 KTS --- 72 HRS, VALID AT: 030600Z9 --- 44.7N5 141.4E0 MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT EXTRATROPICAL --- REMARKS: 310900Z3 POSITION NEAR 36.1N0 124.6E3. TYPHOON (TY) 20W (PRAPIROON), LOCATED APPROXIMATELY 135 NM WEST OF KUNSAN, KOREA, HAS TRACKED NORTHWARD AT 20 KNOTS DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 310530Z2 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 65 AND 77 KNOTS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS THAT THE SYSTEM REMAINS SYMMETRIC, WITH CONVECTION CONTINUING TO WEAKEN OVER THE PAST 6 HOURS. 200 MB ANALYSIS INDICATES TY 20W IS NORTH OF THE SUBTROPICAL RIDGE AND IS APPROACHING THE MID-LATITUDE SOUTHWESTERLIES. UW-CIMSS WIND SHEAR PRODUCTS INDICATE MODERATE VERTICAL WIND SHEAR OVER THE SYSTEM AND INCREASING TO THE NORTH OF THE SYSTEM. TY 20W IS FORECAST TO TRACK INCREASINGLY EASTWARD, AS IT MOVES INTO THE MID-LATITUDE WESTERLY FLOW. THE SYSTEM IS FORECAST TO WEAKEN UNDER INCREASING VERTICAL WIND SHEAR AS IT MOVES NORTHWARD. IT IS EXPECTED TO MAKE LANDFALL NEAR HAEJU, NORTH KOREA AT APPROXIMATELY 311500Z0, AND WEAKEN SIGNIFICANTLY AS IT MOVES ACROSS THE KOREAN PENINSULA. AS THE SYSTEM MOVES INTO THE SEA OF JAPAN, IT WILL UNDERGO EXTRA-TROPICAL TRANSITION. JUSTIFICATION FOR AMENDMENT: CHANGE 12 HOUR FORECAST POSITION DUE TO DIRECTIONAL MOVEMENT TOWARD SEOUL. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 310600Z0 IS 26 FEET. REFER TO WWPW30 RJTX FOR ADDITIONAL SEA HEIGHT INFORMATION. NEXT WARNINGS AT 311500Z0 (DTG 311351Z4), 312100Z7 (DTG 311951Z0), 010300Z4 (DTG 010151Z8) AND 010900Z0 (DTG 010751Z4). REFER TO TROPICAL STORM 21W (MARIA) WARNINGS (WTPN32 PGTW) FOR SIX-HOURLY UPDATES.//