BEIJING - High waves are expected on Wednesday and Thursday in the East China Sea due to a strong cold front and tropical storm Prapiroon, China's National Marine Environmental Forecasting Center warned.

The center forecasts waves of up to five meters high from midday Wednesday to noon on Thursday. It issued a yellow alert on Wednesday morning, warning ships and people on affected waters to be careful and urged authorities to take full precautions.

The typhoon, the 21st of the year, will produce waves measuring three to four meters high in seas surrounding the Diaoyu Islands.

Waves up to 3.5 meters high are expected along the northern coast of Zhejiang and Fujian provinces, both in east China.

China has a four-color warning system for strong winds, with red being the most serious, followed by orange, yellow and blue.