5 December 2019
A numbered typhoon warning system has been in use in Hong Kong for a hundred years, with changes and improvements along with advances in meteorological science and information technology. Photo: HK Observatory
A numbered typhoon warning system has been in use in Hong Kong for a hundred years, with changes and improvements along with advances in meteorological science and information technology. Photo: HK Observatory

Hong Kong Observatory: A century of storm signalling

Hong Kong people like to talk about the weather.

The public is familiar with the Hong Kong Observatory’s typhoon warning system – which is in its centennial year this year – yet not many are aware that more than 100 years ago, warning people promptly of impending tropical cyclones was an intractable challenge itself, when there was no television, internet or smartphones that could swiftly disseminate the information.

So how did the Observatory let Hong Kong know so that the city could brace itself for hurricanes back then? Meteorologists at the time would fire a typhoon gun as a callout to stay dry and safe whenever a major storm was about to hit the territory.

From 1884, one year after the foundation of the Observatory, a typhoon gun would be fired whenever gale force winds bore down on Hong Kong.

Additionally, the Observatory would hoist physical warning signs and flags at signal stations around the city.

There were over 40 of them until the mid-20th century, mostly located at police stations, schools and government buildings.

Chief scientific assistant Fung Kwok-chu has worked at the Observatory for more than three decades.

He said hoisting the 25 kg. metal typhoon signs was literally a heavy task that had to be done by two to three people.

“We used the same ‘T’ sign for Typhoon Signal No. 1 and 3. When we changed the signal from 3 to 1, we had to unknot the rope, turn the ‘T’ sign upside down and hoist it up again,” said Fung in an Observatory feature program to mark the 100th anniversary of the storm signaling system.

“It took over 10 minutes to do so. It could be quite harsh in heavy downpours or against strong winds. Our officers often got drenched doing the job.”

Fung was once posted at the Observatory’s Cheung Chau signal station, and sometimes had to hoist the typhoon sign alone at 2 a.m.

Advances in meteorological science and broadcasting technology saw the phasing out of the metal signs.

It was not until 1917 that a numbered signal system, with a seven-tier scale, was introduced by the Observatory.

Since then, the system has undergone many changes.

“Signal No. 1 was the same as today’s Standby Signal No. 1. Signal No. 2 to 5 mean today’s Typhoon Signal No. 8, indicating gale force winds coming from a certain direction,” says the Observatory’s chief scientific officer Choy Chun-wing.

“Signal No. 6 was the equivalent of today’s Typhoon Signal No. 9. The maximum Signal No. 7 was the same as today’s Hurricane Signal No. 10, the highest warning of the current regime.”

In 1930, meteorologists from East Asian countries decided to standardize the region’s various typhoon signal systems to the one ranked from 1 to 10.

The new system was adopted by Hong Kong a year later until 1973.

“Four of the signals, Signal No. 5 to 8, indicated the same levels of gale force winds, the only difference was the directions from which winds were coming. These signals caused much misunderstanding, for example, when Typhoon Signal No. 7 was replaced by No. 5, people might mistakenly think the wind was getting weaker,” Choy said.

“So in 1973 the Observatory introduced today’s four Typhoon No. 8 signals, indicating winds coming from one of four different directions.”

Since the 1970s, the Observatory has been broadcasting territorywide, more comprehensive typhoon information via radio and television, and later through the internet and its smartphone app.

A pioneer in automation and application of information technology, the Hong Kong Observatory has been commissioned by the United Nations World Meteorological Organization to maintain its own website and update real-time global weather data.

Manned signal stations across Hong Kong were closed one by one along with the rapid computerization of observation. The Cheung Chau signal station was closed in 2002, the last one in Hong Kong after 50 years in use, marking the end of an era.

The Observatory will hold guided tours to the station later this year to allow the public to learn about the 100-year history of Hong Kong’s numbered typhoon signal system.

– Contact us at [email protected]


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Signaling problem: Why the Observatory still doesn’t get it

The current regime of warning signals was first introduced in the 1970s. Photo: HK Observatory