Japanese weather officials say Tropical Storm Muifa has formed over the sea east of the Philippines. They warn that it may approach the southwestern prefecture of Okinawa over the weekend.
The Meteorological Agency said a tropical depression developed into the tropical storm at 9 a.m. on Thursday.
The agency said Muifa has a central atmospheric pressure of 1,000 hectopascals, with maximum winds of about 65 kilometers per hour and gusts of up to 90 kilometers per hour.
It said the storm is moving west-southwest at a speed of 20 kilometers per hour and is expected to head north as it develops.
Officials warn the tropical storm could approach Okinawa from Saturday through early next week.
They are calling on people to stay informed of the latest weather updates.