China is announcing tightened marine disaster warning measures for nuclear plants along its southern coast as Tropical Storm Haima blasts ashore at the start of the annual typhoon season.

The official Xinhua news agency said Thursday the measures are based on forecasts that three to four typhoon-triggered storm surges will hit the southeastern coast this year. Countries around Asia are reviewing nuclear safety measures after a tsunami in March caused a nuclear crisis at Japan's Fukushima nuclear plant.

The storm season began in earnest when Haima made landfall Thursday morning, toppling trees and shutting down port operations from southwestern Hainan Island to Hong Kong. China's National Meteorological Center forecast high winds and downpours for Fujian, Guangdong and Hainan provinces as well as Taiwan.

The storm is expected to worsen flooding that has displaced thousands of people in central and southern China. Southwestern Sichuan province was reported Wednesday to have received 111 millimeters of rain in a single day.