The Hong Kong Observatory issued the Standby Signal No 1 on Wednesday evening, as severe typhoon Koinu moves closer to Hong Kong.

Koinu was about 790km east of Hong Kong as of 10pm, and was forecast to move west at about 12 kilometres per hour towards the vicinity of the southern part of Taiwan.

The Observatory said according to the present track, Koinu will skirt the southern part of Taiwan and move towards the coast of eastern Guangdong on Thursday, while maintaining a distance of more than 500km from Hong Kong, adding that the No 1 signal will remain in force for most of Thursday.

It said Koinu is expected to weaken under the influence of the northeast monsoon later in the week, and whether there's the need to issue higher signals depends on how fast Koinu weakens and its distance from the Pearl River Estuary.

“Under the influence of Koinu and the monsoon, there may be squally showers with strong northerly winds locally over the weekend. Winds will be particularly strong in some areas, including offshore and high ground. The weather will be appreciably cooler,” the observatory said.