A woman examines a tree that was blown down by Typhoon Tembin in Taitung, Taiwan, on Friday. Sam Yeh / Agence France-Presse

The interaction between the severe typhoons Tembin and Bolaven, known as the Fujiwhara effect, will bring torrential rains, strong gusts of wind and rough seawater to the southeastern parts of China, a senior weather forecaster said.

"The twin typhoons are likely to rotate around each other if they get close (about 1,500 kilometers), bringing strengthened power," Qian Chuanhai, a typhoon expert at the China Meteorological Administration, told China Daily on Friday.

According to the latest storm image from the National Aeronautics and Space Administration in the United States, Tembin and Bolaven were about the same diameter on Thursday.

Tembin made landfall in Taiwan at about 5:15 am on Friday and will enter the South China Sea at a speed of 10 km/h on Friday, bringing waves with a maximum height of 8 meters, according to the National Marine Environmental Forecasting Center.

Bolaven was intensifying at about 1,570 km southeast of Zhejiang province on Friday, packing winds of 162 km/h and was moving northwestward at 15 to 20 km/h, according to the CMA.

Qian said two storms of similar size will eventually merge but if the two storms are of unequal size, the larger one will tend to dominate the interaction with the smaller storm orbiting around.

"The Fujiwhara effect adds a layer of difficulty in predicting the routes of the two storms," he said.

In Tembin's forecasted path, Fujian has made full preparations for the coming storms. According to the Fujian Provincial Department of Ocean and Fisheries, about 40,000 boats had been ordered to return to port as of 11 am on Friday. The evacuation work of marine staff is under way.

As the Fujian Meteorological Bureau kept the typhoon alarm on the orange level, the second-highest level, on Friday, the local authorities urged people to stop working on outdoor projects in the province's coastal cities.

Chen Rongkai, vice-governor of Fujian and director of the Fujian Provincial Flood Control and Drought Relief Headquarters, said patrols along dams and embankments have been reinforced to prevent flooding.

Zhang Ling, a chief weather forecaster of the National Meteorological Center, said torrential rains and strong gales brought by Tembin will linger in Fujian and Guangdong provinces before the end of August.

Although Bolaven had little impact this week, it is likely to make landfall in Zhejiang or head to northern parts of the country on Monday, Zhang said.

If the violent cyclone moves north, Northeast China's Liaoning province may face severe flooding, according to the Liaoning Provincial Flood Control and Drought Relief Headquarters.

In the coming 10 days, the two typhoons will bring torrential rain and gales to Guangdong, Fujian, Zhejiang, Jiangsu, Shandong, Liaoning, Jilin and Heilongjiang provinces and Shanghai, with the maximum precipitation volume reaching 300 millimeters, according to the weather forecast released by weather.com.cn on Friday.

The temperature will decrease by 3 to 8 C in most parts of the country at the end of August, the forecast said.

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