The Observatory said on Friday morning that it would issue the Strong Wind Signal Number 3 at 5.40pm as typhoon Koinu edges closer to the coast of Guangdong province.

The forecaster says Koinu has strengthened slightly in the past few hours, but it's expected to weaken under the influence of the northeast monsoon as it approaches the Pearl River Estuary.

Lee Tsz-cheung, a senior scientific officer, says the likelihood of a higher warning will depend on various factors.

"Under the influence of the northeast monsoon, Koinu will weaken slightly over the coastal waters of eastern Guangdong. However, it will edge closer to the vicinity of the Pearl River Estuary gradually, " he said.

"The need for issuance of higher tropical cyclone warning signals depends on its intensity and its distance from the Pearl River Estuary when it edges closer to the region."

Lee Shuk-ming, another senior scientific officer, said that local winds will strengthen gradually on Friday.

"There will be swells. Members of the public are advised to stay away from the shoreline and not to engage in water sports," she said.

The Standby Signal Number One remained in force.