The forecaster said the No 8 alert, issued at 2.40am on Friday, would remain in force for most of the day, adding Saola would be “rather close” to Hong Kong in the evening and on Saturday morning, passing within 100km (62 miles) south of the city.
“Saola has a well-defined eyewall and compact circulation,” the Observatory said on Friday, referring to the turbulent region surrounding the eye of the storm, characterised by intense weather conditions. “As Saola continues to edge closer to Hong Kong, weather will deteriorate rapidly later today. There will be heavy squally showers and violent winds.
“The Observatory will assess the need to issue higher tropical cyclone warning signals around this evening.”
The forecaster earlier said the alert could be raised to a No 10 warning signal if wind speeds reached hurricane levels at offshore and high ground areas over the next two days.
Hurricane force winds were recorded in the vicinity of Shanwei, about 15km to the east of the city, the Observatory on Friday said.
It warned there might be serious flooding as water levels in low-lying coastal areas would rise rapidly on Friday evening.
The Observatory said the problem might be particularly serious along the eastern coastal areas of the city, especially in Sai Kung, Shing Mun River, Tai Po and Sha Tau Kok.
“The maximum water level may be similar to when Mangkhut hit Hong Kong in 2018,” it said, referring to a super typhoon that ripped through the city in 2018, prompting a No 10 signal.
Former Observatory assistant director Leung Wing-mo on Friday warned that the impact of Saola would be “significant” if it hit the city directly, saying the fact that the weather forecaster had announced it would issue the No 8 signal hours before it came into effect reflected the magnitude of the threat.
He added that warning the public in advance was a good move, but conceded there could be potential errors in the forecast.
Leung stressed that it was too early to predict the impact of the typhoon as it depended on how close it would come to the city when it passed by.
The No 8 warning signal brought the city to a halt on Friday, with the Airport Authority saying at least 366 flights had been cancelled and another 40 delayed.
All but one flight operated by Hong Kong’s flagship airline Cathay Pacific Airways to and from the city between 2pm on Friday and 10am on Saturday had been cancelled. The carrier also issued warnings about additional delays and cancellations.
Hong Kong Express and Hong Kong Airlines cancelled about 70 and 36 flights, respectively, on both days. In-town check-in services have also been suspended.
All high-speed rail link services between Hong Kong West Kowloon station and mainland China will be cancelled from Friday noon to Saturday. At least 30 trains have been suspended so far.
The MTR Corporation said there would be limited services under the No 8 signal, with all lines operating at intervals of 10 to 20 minutes, while bus services would be suspended.
The light rail in the New Territories will run at intervals of 15 to 20 minutes, but routes 614 and 615 will not be in service.
Services on open sections of the railway would be suspended immediately without prior notice if weather conditions worsened or a higher warning signal was issued, it added.
Most routes operated by KMB, Citybus and Long Win Bus were suspended, except some services to and from the city’s border control points.
All ferry services between Hong Kong island and outlying islands and Macau are suspended.
Hong Kong Exchanges and Clearing announced that the morning trading sessions for all markets had been cancelled on Friday.