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What to expect in typhoon season

By: Cassilda Lee

Typhoon season in Hong Kong typically begins from May to early November. The peak period lasts from July to September. According to the Hong Kong Observatory typhoon season can see multiple typhoons affect the city. To help you navigate safely through this period, Hong Kong has a warning system in place.

What exactly is a typhoon, and how is it different from a hurricane?

Despite much confusion, they’re actually the same weather phenomenons. Both are simply tropical cyclones – a rotating, organised system of clouds and thunderstorms. They mainly differ in the locations they’re formed or appear in. A typhoon is formed over the Northwest Pacific while a hurricane are those over the Atlantic.

The phenomenon occurs when air rises due to warm sea water, creating a rotating cycle as the air heats and cools above the surface. This results in the strong winds, heavy rains, and even floods typically associated with the cyclones. When winds hit a maximum sustained speed of 118 km/h near the centre, it’s officially categorised as a typhoon. At speeds of 185 km/h or more, this becomes a Super Typhoon.

image of Hong Kong sky during typhoon season

Typhoon Warning System

Signal No.1 (Referred to as a T1): Indicates a tropical cyclone that has its centre about 800 km from Hong Kong, and may affect the territory. People are advised to stay alert and keep updated through regular announcements for any changes.

Signal No.3 (Referred to as a T3): Indicates strong winds are expected (41 to 62 km/h), or blowing generally towards Hong Kong near sea level, with gusts that may exceed 110 km/h. Public transport still runs but harbor cruises, flights, stores and business might close or be cancelled. Loose objects should be secured, and you’re advised to stay away from the shoreline. 

Signal No.8 (Referred to as a T8): Stronger winds up to 102 km/h are expected, and gusts up to 180 km/h or more are imminent. Everything will be closed or shut down. Before a signal 8 is issued, plenty of warning is given several hours in advance. This gives the public a chance to return home or go to a safe place. Precautionary measures should be taken before the gale begins (locking windows and doors, adhesive tape fixed to large, exposed window panes to reduce damage by broken glass).

Signal No.9 (Referred to as a T9): Winds up to 102 km/h are increasing, or expected to increase significantly in strength. Everyone should stay indoors and away from exposed windows or doors to avoid flying debris. Children should be secured in the least exposed part of homes and do not touch electrical cables that have been blown loose.

Signal No.10 (Referred to as a T10): Sustained wind speeds upwards from 118 km/h are expected, with gusts that may exceed 220 km/h. The same precautions as above apply, and you are advised to stay alert even if there may be a temporary calm as the centre of the typhoon passes over Hong Kong.

Safety precautions during typhoons include taping windows to minimise the chance of flying glass in the event of winds blowing in windows. You should also remove loose items from outdoor areas and balconies. The MTR frequency rises to peak-hour levels to allow people to get home as quickly as possible.

image of Tung Chung during typhoon season
Damage caused by a T10 in Tung Chung

Major Typhoons

To explain what a big deal a no.10 is, there have only been 15 no.10 typhoons since 1946. Often, these leave huge trails of destruction. Take a look below for some of Hong Kong’s worst typhoons.

Typhoon Mangkhut, in September 2018, was a no.10 and titled a Super Typhoon. The signal no. 10 remained active for 10 hours. The damage to the city was serious and extensive. You can see some images of the damage here. For Super Typhoon Mangkhut, injuries were reported as five times higher than Typhoon Hato from the previous year.

Typhoon Hato, in August 2017, was a no.10 typhoon. There was at least 129 injuries, over 5,300 reports of fallen trees, and more than 480 cancelled flights. “Hato” momentarily gained super typhoon intensity over the sea areas south of Hong Kong, reaching an estimated speed of 185 km/h near its centre.

While Typhoon Vincente did not result in any casualties in 2012, it still caused much damage.  It caused 138 injuries, 8,800 felled trees and numerous landscape damages. Hundreds of commuters were forced to stay overnight in trains or at MTR stations due to toppled trees and fallen scaffolding.

Ranking highest in terms of injuries sustained (500 people), Typhoon York (1999) also held the record at the time for the longest duration in which the No.10 signal was in place. During its passage, a maximum hourly wind of 151 km/h was recorded at Waglan, over 4,000 trees were uprooted, and 90 roads were rendered impassable.

Typhoon Ellen (1983) was a slow moving cyclone, with the No.10 signal being hoisted for a total of eight hours, and hurricane force winds lasting for five hours at Cheng Chau. During its run, 10 people were killed, 12 went missing and 333 were injured. A maximum gust of 237 km/h was recorded at Cheng Chau, the strongest there since 1953.

Despite its positive sounding name, Typhoon Hope (1979) resulted in 12 deaths, 260 injuries, and around 2000 people were forced to stay in temporary shelters due to the damage. A maximum gust speed of 200 km/h was recorded at the Star Ferry pier. This was the highest gust recorded inside the harbour since Typhoon Rose.

In August 1971, Typhoon Rose tore through Hong Kong and left 110 deaths, five missing and 286 injured in its wake. An unusual fog was also observed during Rose at Waglan Island, a rarity in Hong Kong in August. Rose was the most severe typhoon for fatalities and heavy damage since Wanda in 1962.

Typhoon Wanda is arguably Hong Kong’s most intense cyclone. It claimed 130 lives, 53 missing, and left at least 72,000 people homeless. The hourly wind speed of 68 knots (126 km/h) was the second highest on record at the time, with speeds even averaging about 78 knots (144 km/h) for a short period.

For weather updates and typhoon information go to the Hong Kong Observatory website.

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