WTJP21 RJTD 150600 WARNING 150600. WARNING VALID 160600. WARNING IS UPDATED EVERY 6 HOURS. STORM WARNING. SEVERE TROPICAL STORM 1607 CHANTHU (1607) 985 HPA AT 27.9N 144.4E OGASAWARA SHOTO MOVING NORTH 09 KNOTS. POSITION FAIR. MAX WINDS 50 KNOTS NEAR CENTER. RADIUS OF OVER 30 KNOT WINDS 210 MILES EAST SEMICIRCLE AND 120 MILES ELSEWHERE. FORECAST POSITION FOR 151800UTC AT 29.8N 143.0E WITH 40 MILES RADIUS OF 70 PERCENT PROBABILITY CIRCLE. 980 HPA, MAX WINDS 55 KNOTS NEAR CENTER. FORECAST POSITION FOR 160600UTC AT 31.8N 141.5E WITH 60 MILES RADIUS OF 70 PERCENT PROBABILITY CIRCLE. 985 HPA, MAX WINDS 50 KNOTS NEAR CENTER. EXTENDED OUTLOOK. FORECAST POSITION FOR 170600UTC AT 38.1N 141.6E WITH 150 MILES RADIUS OF 70 PERCENT PROBABILITY CIRCLE. 985 HPA, MAX WINDS 50 KNOTS NEAR CENTER. FORECAST POSITION FOR 180600UTC AT 50.3N 145.5E WITH 220 MILES RADIUS OF 70 PERCENT PROBABILITY CIRCLE. 984 HPA, MAX WINDS 50 KNOTS. BECOMING EXTRATROPICAL LOW. JAPAN METEOROLOGICAL AGENCY.=