The Hong Kong Observatory will issue the No 1 standby signal on Wednesday night as it has predicted that a tropical cyclone will move within 800km (497 miles) of the city, with another intensifying in the region.

The weather forecaster said at around noon on Wednesday the cyclone, which has yet to be named, would intensify gradually and move in the general direction of the coast of eastern Guangdong province over the next couple of days.

It will bring winds, heavy showers and thunderstorms on Friday and over the weekend.

“Under the influence of the outer rainbands associated with the tropical cyclone, the local weather will become unsettled on Friday,” the Observatory said.

“It will be windy with occasional heavy squally showers and thunderstorms over the weekend. There will be swells.”