The Observatory issued the No 8 Southeast Gale or Storm signal at 9.20pm on Sunday as Tapah intensified into a severe tropical storm.

Forecasters said the No 8 signal will remain in force until at least 11am on Monday, and that the chance of higher signals is "relatively low" unless the storm adopts a track closer to the Pearl River Estuary or strengthens significantly.

At 10pm, Tapah was about 250 kilometres south-southwest of the SAR and is forecast to move northwest or north-northwest at about 18 kilometres an hour, edging closer to the coast of western Guangdong.

According to the present forecast track, it will skirt within 200 kilometres southwest of Hong Kong around sunrise on Monday before making landfall over western Guangdong.

Local winds are expected to strengthen further on Sunday night and Monday, and there will be squally heavy showers and thunderstorms.

Classes of all day schools on Monday – including secondary schools, primary schools, special schools, kindergartens and kindergarten-cum-child care centres – have been suspended.

And with the No 8 signal in force, the Hong Kong-Macau Ferry Terminal in Sheung Wan and the China Ferry Terminal in Tsim Sha Tsui have been closed temporarily.

Air traffic are also being disrupted with several airlines announcing the cancellation of flights. Passengers are being urged to check with the airlines for the latest flight information.