This story has been made freely available as a public service to our readers. Please consider supporting SCMP’s journalism by subscribing.The Hong Kong Observatory issued the No 1 typhoon signal at 7.40am on Thursday as an approaching tropical cyclone moved south of the city.The centre of the tropical cyclone was about 800 kilometres (497 miles) from Hong Kong, according to the weather forecaster, which said it would assess whether to issue the No 3 strong wind signal on Friday.“The tropical depression will intensify gradually and move in the general direction of Hainan Island today, maintaining a distance of 500 kilometres or more from Hong Kong. The Standby Signal No 1 will remain in force [on Thursday],” the Observatory said.At 8am, the tropical depression over the central part of the South China Sea was estimated to be about 630 kilometres south of Hong Kong and was forecast to move west-northwest at about 22km/h (13.7mph), in the general direction of Hainan Island.With the tropical cyclone edging closer to the coast of southern China, local winds would gradually strengthen on Friday, the forecaster said.