Hong Kong, Sept. 24 -- Typhoon Ragasa forced this city into one of its rare, full-scale shutdowns on Wednesday as the Hong Kong Observatory hoisted the Hurricane Signal No. 10 and hurricane-force gusts drove seawater into coastal shops, hotels, and ferry piers. The storm then curved west toward Guangdong's refinery belt, where authorities evacuated large populations and warned of dangerous storm surges along the Pearl River Delta. By nightfall, conditions in Hong Kong had eased enough for forecasters to begin stepping warnings down, but the cleanup, flight backlog, and regional flood risk signaled a longer recovery arc across southern China.

The escalation through the city's warning ladder was unusually rapid, with Signal No. 8 and Signa...