It said that it had recorded maximum sustained winds of 109 kilometres an hour at Ngong Ping, with maximum gusts of 134 kmh.
At 7pm, Tropical Storm Lionrock was centred about 520 kilometres west-southwest of Hong Kong and was moving slowly northwest.
The Observatory issued the Amber rainstorm signal at 1pm and repeated earlier warnings of possible flooding in low-lying areas, and urged the public to stay away from watercourses, and the shoreline.
The tropical storm brought gloomy weather and some disruption to the city throughout the day, with bus services, day and evening classes suspended.
The Airport Authority said while most passenger flight journeys went ahead as scheduled, 12 flights were delayed, five flights were cancelled, and three flights were rerouted to other airports.
The tropical storm also affected other aspects of the city’s life.
“A Symphony of Lights”, the daily daily light and sound show across Victoria Harbour, and the Mark Six lucky draw were cancelled.
However, apart from the downpour and some reports of fallen trees, the weather appeared less extreme than previous tropical storms.
Festival Walk was crowded with shoppers and many shops and restaurants were open, and it was a similar story at Prince Edward.
Separately, the Home Affairs Department said it had opened 20 temporary shelters and 75 people had sought refuge.
As of 4pm, authorities had received 114 reports of fallen trees, three landslide reports and two confirmed flooding cases.
The Hospital Authority said nine people – two men and seven women – had sought medical treatment during Lionrock.