When a typhoon hits
HONG KONG
Anatomy of a typhoon
What is the city like during a T10?
Dive into the science
How frequent are typhoons in Hong Kong?
Hong Kong classifies tropical cyclones based on the World Meteorological Organization's system, which uses maximum sustained wind speeds near the centre.
The city also uses a local warning signal system to alert people and ensure they can prepare accordingly.
The Observatory’s current warning signal system was established in 1973.
It begins with the T1 standby signal, issued when a typhoon is within 800km of the city, followed by the T3 strong winds signal, and escalating to T8-T10 signals for stronger gales and hurricane-force winds.
Even if the storm is located hundreds of kilometres away from the city, the Observatory has repeatedly warned that huge waves whipped up by high winds known as swells can could travel much further away from the centre.
Members of the public are therefore advised to stay away from the shoreline and avoid engaging in water sports even during T1, when the weather may appear calm.
Hong Kong’s typhoon season is from May to November, with the most active period being July to September. Each year, around five to six typhoons come within 800km of the city, triggering about 16 warning signals.
A typhoon can form only if certain conditions are met.
First and foremost, it needs very warm ocean water for energy. It also requires a generally stable atmosphere – meaning the wind is not changing too much with height – to allow the storm to organise itself.
While cyclones that form over the ocean in the tropical regions are generically called "tropical cyclones", they are also known by different names in different ocean basins. For example, they are called "typhoons" in the western North Pacific, "hurricanes" in the North Atlantic and "cyclonic storms" in the North Indian Ocean.
The movement of tropical cyclones usually depends on their interactions with other weather systems nearby, such as the subtropical ridge. Some tropical cyclones that form over the seas east of the Philippines tend to move northwestwards towards the South China Sea and even the coast of Guangdong, where Hong Kong is located.
Since 1956, northeast and southeast No 8 gale signals have been more than twice as common in Hong Kong as northwest and southwest ones.
Tides of change
How has the city’s vulnerability shifted over time?
Apart from typhoons, Hong Kong is also facing challenges such as more extreme rainstorms and rising sea levels because of climate change.
In 2021, the government completed a coastal hazards study and identified 26 low-lying or windy residential areas and planned improvement measures to safeguard public safety.
Measures undertaken including improving drainage works, setting up removable flood barriers, and designing coastal buffer zones and floodable areas.
Before the days of early warnings and modern-day preparations, typhoons were devastating forces that claimed hundreds of lives and shaped the city's history.
Our typhoon vibe
How do Hongkongers cope nowadays?
These days, Hongkongers have a different view of typhoons.
Thanks to early warnings and solid infrastructure, severe storms are less of a life-threatening disaster and more of a welcome interruption.
This is why many people secretly hope for a T8 signal, which used to guarantee a day off from the office.
For some families, a well-timed typhoon means an impromptu all-night mahjong session.
For decades, the city's business sector faced massive financial losses whenever typhoons forced the stock and futures markets to shut down. It gave birth to a satirical urban legend: the city was protected by a "force field" created by Li Ka-shing, Hong Kong's longtime richest man, to keep typhoons from disrupting the workday.
The rumour started after Typhoon Prapiroon in 2006. Many Hongkongers felt intense winds, but the Observatory issued only a No 3 signal, based on a single wind monitoring station at Victoria Harbour.
In response to widespread public complaints, the Observatory expanded its network to include several monitoring stations across the city, according to its annual typhoon report.
Still, the jokes persist. Every time a typhoon suddenly weakened or changed direction, Hongkongers would jokingly credit Li's field.
It also reflects a shared sense of humour if not irony frustration that major storms often hit at weekends or at night – denying the city a free day off.
Is it true?
But for many, the old "typhoon day" no longer exists.
After the pandemic, hybrid work became more prevalent, making working from home a common reality.
The Labour Department usually reminds employers to make prior work arrangements for employees during and after tropical cyclone warnings. Those arrangements should include reporting for duty, release from work, resumption of work and remote work, and vary based on each event.
Employers are also required to conduct a “timely and realistic assessment” of the need for employees to go to the workplace in a safe manner. If citywide “extreme conditions” announcement is issued, employees should stay in the place they are currently in or in safe places, instead of heading for work.
Hong Kong’s financial markets also changed their approach, scrapping a 70-year tradition of closing during storms as of last September. While transport, retail, and catering sectors are still hit hard, online trading and digital banking keep the economic engine running, even during a storm.
