Super typhoon Soudelor is generating waves of about 15m as it heads towards Taiwan, according to the Joint Typhoon Warning Centre.
The storm had sustained winds of 241km/h, with wind gusts of 296km/h.
Nasa snapped pictures of the storm from space.
The US space agency said the storm contained "powerful thunderstorms": "This super typhoon was generating extremely rough seas, with maximum significant wave height to [14.6m]," Nasa said. The typhoon, the most powerful of the year, is tracking over mostly open ocean but will near Japan's remote Ishigaki island today before passing over northern Taiwan.