, Packing gusts of up to 205 kilometres (127 miles) per hour, the storm is projected to roar between the Philippines and Taiwan before smashing into the southern Chinese coast later in the weekend.
At 0300 GMT Friday it was centred 1,160 kilometres southeast of Hong Kong, officials in the Chinese territory said.
“It is the strongest typhoon in the west Pacific region this year,” a weather forecaster at the Taiwan Central Weather Bureau told AFP.
Philippines authorities issued a signal four alert for the Batanes island group in the extreme north of the country, warning large trees could be uprooted, plantations flattened and power and communications infrastructure knocked out.
“Damage to affected communities can be very heavy,” the Philippine Atmospheric, Geophysical and Astronomical Services Administration said. “The situation is potentially very destructive to communities. All travel and outdoor activities should be cancelled.”
The country’s National Disaster Risk Reduction and Management Council said Usagi would cause intense rainfall of 10-20 millimetres per hour within a 700 kilometre range.
Hong Kong officials warned of worsening weather in the southern Chinese territory.
“Weather will deteriorate significantly with strengthening winds and rough seas,” the Hong Kong observatory said. Its tropical cyclone track map showed the storm would hit the city after 8:00 pm (1200 GMT) on Sunday.
The typhoon is expected to be downgraded to “severe” by the time it makes landfall in the territory, according to the observatory.
Typhoon Usagi is set to brush the southern tip of Taiwan on Saturday morning, expected to bring fierce winds and torrential rains, possibly leading to landslides.
The Taiwan weather bureau issued a warning to the residents of Taitung, Kaohsiung and the Pingtung areas to take special precautions, as television news footage showed people surfing on waves whipped up by Usagi.
Officials in southeastern Taitung county ordered the suspension of ferries.
And authorities in the southern city of Kaohsiung deflated an 18 metre tall (60 feet) yellow duck, a slightly larger version of the one that recently captivated people in Hong Kong, a day after it arrived in the city, drawing tens of thousands of visitors.
Mainland Chinese weather authorities have issued a “yellow” alert, state media reported, the third highest on its four tier warning system, according to the official official Xinhua news agency.
China’s State Oceanic Administration expects Usagi to hit the coast between south China’s Guangxi Zhuang Autonomous Region and southeastern Fujian Province on Sunday evening.
Typoon Utor, which struck last month, killed eight people in the Philippines and left tens of thousands displaced and whole towns badly damaged when it raked across the north of the main island of Luzon.
Utor, which also led to deaths in China, forced the closure of financial markets, schools and businesses in Hong Kong, disrupting hundreds of flights and also caused the sinking of a 190-metre-long cargo ship to the city, but all 21 crew were rescued.
A super typhoon is the most intense tropical cyclone, with a maximum sustained wind speed reaching 185 km/h or above.