Tropical Storm Yun-yeung is forecast to approach central and eastern Japan as early as on Friday afternoon and may make landfall later in the day.
The Japan Meteorological Agency says that as of 3 a.m. on Friday, Yun-yeung was situated over Pacific waters 170 kilometers southeast of Wakayama Prefecture and moving north at a speed of about 15 kilometers per hour.
Rain is intensifying in eastern areas along the Pacific, with Kozushima Island of the Izu Islands recording a downpour of 136.5 millimeters in six hours through 5 a.m.
Strong rain prompted a mudslide alert to be issued for part of the Izu Islands.
Thunderstorms may hit the central region of Tokai through Friday night, the eastern region of Kanto through Saturday, and the northeastern region of Tohoku from Friday night through Saturday.
Bands of heavy rain clouds may form over the Izu Islands through Friday morning and the Kanto-Koshin region through Friday night, bringing downpours that could sharply raise the risk of disasters.
The total rainfall for the 24-hour period through Saturday morning could reach 250 millimeters in Kanto-Koshin and Tokai, 200 millimeters in the Izu Islands, and 120 millimeters in Tohoku. Precipitation could grow further if bands of heavy rain clouds develop.
Weather officials are calling on people to stay vigilant for mudslides, flooding and swollen rivers as well as strong winds, high waves, lightning and gusty winds.