Super-typhoon Usagi reached category 5 strength Thursday, and continued to grow as it moved toward Hong Kong Friday. Its peak winds intensified dramatically in two days, from 75 mph to over 160, making it the strongest storm of the year so far.
The storm passed over very warm waters on Thursday — up to 86 degrees Fahrenheit — which added more energy to the storm.
Usagi’s passage near the Philippines prompted evacuations in the north, and Taiwan has issued an “Extremely Torrential Rain Advisory” for much of the island. The center of the typhoon is expected to pass just south of Taiwan, causing heavy rains, strong winds, and a storm surge on its south and east coast tonight and Saturday.
China issued a yellow alert for the incoming storm, with red being the only more severe warning. The storm is expected to weaken before making landfall near Hong Kong on Sunday, though it could end up significantly to the north or west of the city of over seven million.
But Hong Kong is a city at risk for major flooding from a large storm surge. A report by Wyss WS Yim of the Guy Carpenter Asia-Pacific Climate Impact Centre, found that Hong Kong is at risk for coastal flooding, with 15% of its total land area dangerously close to sea level, and a “trough effect” caused by extensive land reclamations.
And while the city’s “cliffed coastal topography” makes it less susceptible to the consequences of sea level rise, a 2007 report from the Hong Kong University of Science and Technology Lau et al said that if the IPCC’s mean estimation of sea level rise comes to pass, 50-year floods could happen every three years. If sea levels rose by the IPCC’s upper best estimate, 50-year floods would occur yearly.
Hong Kong’s most recent major typhoon was Ellen in 1983, which killed 10, left 345 injured or missing, and sunk or damaged 260 oceangoing vessels.