| Hong Kong Tropical Cyclone Warning Signals |
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The signals are represented as a set of numbers, symbols and lights. HISTORY Beginning in 1884 , a combination of Drum s, Ball s and Cone s was hoisted to alert Mariners in the Harbour of an approaching tropical cyclone. On the other hand, the warning was given to the general public using a Typhoon Gun . The gun was replaced by Bombs in 1907 , as the bombs made louder sounds and were considered an improvement. The last typhoon bomb was detonated in 1937 . The first numbered warning signal system was introduced in 1917 . The numbers ranged from 1 to 7, with 2 to 5 signifying gale force winds expected from the four Quadrant s. The system was amended in 1931 with the numbers 1, 5, 6, 7, 8, 9 and 10, with 5 to 8 signifying gales from the four quadrants. The No. 3 Strong Wind Signal was introduced in 1956 as an intermediate warning between the No. 1 Stand By Signal and the gale signals. In the past, the signals were physically hoisted at many locations in Hong Kong; there were 42 Signal Station s around the territory in the 1960s . However, as Radio and Television Weather Report s became increasingly effective, the need to hoist physical signals diminished. The last signal station, Cheung Chau Aeronautical Meteorological Station on Cheung Chau , was decommissioned on 1 January 2002 . Accordingly, the observatory has replaced the word ''hoist'' with ''issue'' in its official terminology, although the phrase "Signal No. __ has been hoisted" is still widely used by the public. CURRENT SYSTEM Starting from 1 January 1973 , signals 5 to 8 were replaced by 8 NW, 8 SW, 8 NE and 8 SE respectively so as to avoid misunderstanding by the public. This system has been in use ever since. In accordance with legal codes and common practices in Hong Kong, once any signals higher than No. 3 are issued, all government agencies will shut down their operations. Schools will immediately cease their sessions, as well the financial markets and a majority of the private sector. Public transit agencies that operate on the sea or on surface streets and highways will either cease or scale back their operation. In an effort to minimise the disruptions and stress caused by the exodus of office workers from their workplace, the Hong Kong Observatory usually gives the city an advance warning of about two hours before actually issuing Signal No. 8. As the system was originally intended to serve as warnings for mariners, the issuance of signals were based on wind speeds measured around the Victoria Harbour . However, the system has also been adopted for use by the public over the years, and with ongoing urbanization, some have come to question the relevance of the warning system's mechanism in this day and age, citing the following reasons:
Starting from the tropical cyclone season in 2007 , the signals will be issued based on a network of 8 near sea-level reference anemometers over Hong Kong. MEANING OF SIGNALS The official definitions of the signals are as follows:
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