Weather officials are urging vigilance after Tropical Storm Trases formed over waters just north of the main island of Okinawa in southwestern Japan.
The Meteorological Agency said a tropical depression developed into a tropical storm over waters 40 kilometers north of Naha city at noon on Sunday.
Agency officials warn of heavy rain, high winds and high waves as Trases is already approaching the main island of Okinawa.
They say the storm had a central atmospheric pressure of 998 hectopascals, with maximum winds of around 65 kilometers per hour and gusts of up to 90 kilometers per hour.
It is moving north at a speed of 30 kilometers per hour.
Intermittent heavy rain and strong winds are expected, especially over the main island region of Okinawa and the Amami area in Kagoshima Prefecture. The sea should remain rough.
Weather officials are urging people to be alert for landslides, flooding in low-lying areas, sudden swelling of rivers, high winds and high waves.
The storm is expected to continue to move north over waters west of Kyushu and become a tropical depression by noon Monday.
Agency officials are calling on people to stay informed of the latest weather updates.