Typhoon Ketsana grew slightly weaker Sunday as it moved northeast off northeastern Japan in the Pacific, the Japan Meteorological Agency said.
At noon, the season's 17th typhoon was traveling at a speed of 60 kph about 550 km east-southeast of Choshi, Chiba Prefecture.
The typhoon had an atmospheric pressure of 980 hectopascals at its center, packing winds of up to 108 kph.
According to the meteorological agency, the typhoon was expected to wane into an extratropical cyclone Monday.
With forecasts of waves up to 4 meters until Sunday night in the northern part of the Izu Islands and the coastline of the Kanto region, the agency warned the public against leisure activities near the sea.
Ketsana is the Laotian name of a type of tree.