Hong Kong people are familiar with the Hong Kong Observatory’s typhoon warning system.
However, they might not know a typhoon gun was fired to warn the public of impending tropical cyclones in the past.
From 1884, the gun was fired whenever gale force winds bore down on the city. It was not until 1917 that a numbered signal system was introduced.
The system has undergone many changes over the past century.
Numbered notification
The Observatory’s Scientific Officer Choy Chun-wing said the system adopted in 1917 was numbered from 1 to 7.
"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.
"Signal No. 6 was the equivalent of today’s Typhoon Signal No. 9 meaning increasing gale force winds. The maximum Signal No. 7 was the same as today’s Hurricane Signal No. 10."
In 1930, meteorologists from East Asian countries decided to standardise the region's typhoon signal system to one ranked from 1 to 10.
The new system was adopted by the Hong Kong Observatory a year later and used until 1973.
"Four of the signals indicated the same levels of gale force winds coming from four different directions. But they might create misunderstanding. For example, when Typhoon Signal No. 7 was replaced by No. 5, people might mistakenly think the wind was getting weaker.
"So in 1973 the Signal No. 5 to 8 system was replaced by today’s four Typhoon No. 8 signals, indicating winds coming from one of four different directions."
The Observatory hoisted physical warning signs at signal stations around the city to warn the public of approaching typhoons.
There were over 40 of them in the 1960s, with most located at Police stations or Marine Department buildings.
Police and marine officers, and the observatory’s scientific assistants, hoisted the warning signs.
Tough task
Chief Scientific Assistant Fung Kwok-chu has worked at the Observatory for more than three decades.
He said hoisting the 25kg metal typhoon signs was a challenging 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 1 to 3, we had to unknot the rope, turn the 'T' sign upside down and hoist it up again.
"It took over 10 minutes to do. It could be quite harsh doing it in bad weather, with heavy downpours and strong winds. Our officers often got drenched doing the job."
Mr Fung used to be posted at the Observatory's Cheung Chau signal station.
He said he used to hoist the typhoon sign alone at 2am.
"The winds were very strong. I heard a loud bang when I was putting it up. I thought the sign hit something.
"But it turned out the sound came from the gate which banged closed because of the winds. The experience was scary but unforgettable."
Modern meteorology
Advances in technology saw the phasing out of the metal signs.
Since the 1970s, the Observatory has broadcast comprehensive and up-to-date typhoon information via radio and television.
Signal stations were closed one by one.
The closing of the Cheung Chau signal station in 2002, the last one in Hong Kong, marked the end of an era.
The station was set up in 1953 on top of a hill.
It was manned by scientific assistants who had to observe the weather and hoist the typhoon warning signs.
The station was automated in 1992 and scientific assistants were no longer posted there.
Today, the station stores the old warning signs and historic photos.
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.