HONG KONG - Hong Kong residents are bracing themselves for the wrath of the worst typhoon of the year as they await Super Typhoon Mangkhut’s arrival on Sunday (Sept 16).

The Hong Kong Observatory on Saturday raised its alert from No. 3 strong wind signal to No. 8 gale or storm signal, and warned it could be moved up to the No. 10 typhoon signal on Sunday.

No. 10 is the highest of the city’s tropical cyclone warning signals. It indicates that hurricane-force wind is expected or blowing with sustained speed reaching upwards of 118kmh and gusts that may exceed 220kmh.

The Observatory urged residents to complete preparations as early as possible with the winds due to pick up on Saturday night.

Its assistant director Cheng Cho Ming said in a radio show on Saturday that having swept through the Philippines, Mangkhut had weakened but the typhoon remained strong and threatened southern China's Guangdong region.

He said Hong Kong would not be spared, adding: “Wind strength will grow very quickly after midnight, so if (residents) need to prepare for the storm, it is best if they do it today. The earlier, the better.”

Hong Kong's security minister John Lee Ka Chiu was reported as saying after meeting more than 30 bureaus and departments: "I have ordered all parties to prepare for the worst."

However, there seems to be no great sense of urgency on Saturday.

Groceries deliveryman Khan, 29, told The Straits Times: "We are still delivering the groceries today. There will be no deliveries when the typhoon signal is raised to No. 8."

Others like laundromat operator Grace said the shop will not open on Sunday or Monday “if there’s heavy storm due to safety reasons”. But she told ST she will not be securing her shopfront windows with tape “because the wind may not come this way”.

Hong Kongers are no strangers to typhoons and will usually automatically stock up on food supplies and secure their windows to weather the storm.

A quick check at two supermarkets in the western part of the city found that prices of meat and vegetables have risen by as much as twice.

A bookshop owner, who gave her name as Mrs Leung, said the best brands of masking tape had been sold out. “The price at our shop is still affordable at HK$10 (S$1.75) but at other places, one roll costs HK$50,” she said. “It happens when some businesses seek to profit from the circumstances.”

Mangkhut, expected to cross the South China Sea and strike Guangdong on Sunday, ripped into the northern Philippines early on Saturday with winds of up to 269kmh.

The US Navy and Air Force’s Joint Typhoon Warning Centre in Hawaii said by US standards, it was a Category 5 storm on the five-step Saffir-Simpson scale.

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The super typhoon could cause US$120 billion (S$165 billion) worth of damage, Bloomberg reported. Of that, China could absorb about US$100 billion, of which US$26 billion is projected to be in Hong Kong alone, according to Mr Chuck Watson of Enki Research in Savannah, Georgia.

“Any big storm going into the Hong Kong area, talk about a target-rich environment. That is just ugly,” he said.

In a worst-case scenario, if the eyewall of the typhoon hits Hong Kong head-on, about 48km north of official forecasts, the economic impact could rise to US$135 billion for the territory alone and US$230 billion for China overall, he added.

Cathay Pacific Airways said it was expecting “severe disruptions with more than 400 cancelled flights in the next three days”. All flights will be cancelled between 2.30am on Sunday and 4am on Monday.

Last Friday, Chief Executive Carrie Lam cautioned against “storm-chasing”.

The Civil Aid Service helped residents of Lei Yue Mun and Tai O, areas at risk of serious flooding, to move their belongings.