Weather officials in Japan say Typhoon Chanthu is moving north-northeast over waters south of Okinawa. It is likely to make a close approach to Okinawa's Yaeyama region on Sunday.
The Meteorological Agency says the typhoon was moving about 15 kilometers per hour as of 9:00 p.m. on Saturday, Japan time.
It has a central atmospheric pressure of 920 hectopascals, and central winds of 198 kilometers per hour, with gusts up to 270 kilometers per hour.
The typhoon is likely to continue moving north and approach the Sakishima Island chain in Okinawa Prefecture on Sunday afternoon while retaining its power.
The agency is advising people in the region to be on high alert for violent winds.
Vigorous winds of up to 162 kilometers per hour are forecast for the Yaeyama region, including the islands of Yonaguni and Ishigaki, shortly after midday on Sunday. Maximum instantaneous winds of 234 kilometers per hour are possible.
The agency is advising people in the region to evacuate to strong buildings before stormy winds begin to blow, and stay indoors away from windows.
It says in past typhoons of this level, winds knocked down utility poles and concrete block walls, and turned vehicles on their sides.
Rough seas are forecast for the Yaeyama region by daybreak on Sunday. Waves will become as high as ten meters shortly before midday.
Developed rain clouds from the typhoon will shroud the Sakishima Islands, bringing extreme rain there.
Over the 24 hours until Sunday evening, 180 millimeters of rain will fall in the Okinawa region.
In the next 24-hour period to Monday evening, 100 to 150 millimeters of rain are forecast.
Caution is also advised for possible lightning strikes and gusts of wind.