WTJP21 RJTD 031800 WARNING 031800. WARNING VALID 041800. WARNING IS UPDATED EVERY 6 HOURS. TYPHOON WARNING. TYPHOON 1821 JEBI (1821) 945 HPA AT 30.3N 132.8E SEA SOUTH OF JAPAN MOVING NORTH 16 KNOTS. POSITION GOOD. MAX WINDS 85 KNOTS NEAR CENTER. RADIUS OF OVER 50 KNOT WINDS 90 MILES SOUTHEAST SEMICIRCLE AND 60 MILES ELSEWHERE. RADIUS OF OVER 30 KNOT WINDS 240 MILES SOUTHEAST SEMICIRCLE AND 180 MILES ELSEWHERE. FORECAST POSITION FOR 040600UTC AT 35.3N 135.5E WITH 40 MILES RADIUS OF 70 PERCENT PROBABILITY CIRCLE. 960 HPA, MAX WINDS 75 KNOTS NEAR CENTER. FORECAST POSITION FOR 041800UTC AT 43.1N 139.2E WITH 80 MILES RADIUS OF 70 PERCENT PROBABILITY CIRCLE. 970 HPA, MAX WINDS 60 KNOTS NEAR CENTER. EXTENDED OUTLOOK. FORECAST POSITION FOR 051800UTC AT 52.8N 136.6E WITH 110 MILES RADIUS OF 70 PERCENT PROBABILITY CIRCLE. 976 HPA, MAX WINDS 40 KNOTS. BECOMING EXTRATROPICAL LOW. JAPAN METEOROLOGICAL AGENCY.=