East China's coastal provinces of Zhejiang and Fujian on Thursday moved in lockstep to activate their Level-IV typhoon emergency response mechanisms as the seventh typhoon of the year approaches, expected to bring strong winds and heavy rains.

At 5 p.m. Thursday, Zhejiang upgraded its existing offshore alert to a Level-IV typhoon alert for Typhoon Francisco. Just five hours earlier, Fujian had issued the same warning, underscoring the shared threat.

At 2 p.m., Francisco's center was located approximately 790 kilometres southeast of the Zhejiang-Fujian border, packing winds of up to 20 meters per second. It is forecast to move northwest at speeds of 15 to 20 kilometers per hour, to enter the southern East China Sea on Thursday evening, and to then approach the coast from southern Zhejiang to northern Fujian.

The situation is complicated by newly minted Typhoon Co-May -- the eighth typhoon of the year.

While Co-May is expected to move northeastward late on Thursday afternoon, its proximity to Francisco could trigger a Fujiwhara interaction, which means that the two storms are likely to begin an intense dance around a shared center.

"The Fujiwhara effect could leave both systems weaker than either would have been alone," said Mao Yanjun, a senior engineer at the Zhejiang Climate Center. "Co-May is likely to downgrade to a depression on its northward trek, and cooler sea-surface temperatures will sap Francisco's strength once it enters the East China Sea."