Hong Kong tropical cyclone warning signals
The Hong Kong tropical cyclone warning signals (Chinese: 熱帶氣旋警告信號), or informally typhoon signals (Chinese: 風球; Sidney Lau: fung1 kau4, literally, "wind balls"), are a set of signals used to indicate the threat or effects of a tropical cyclone. The Hong Kong Observatory issues the warning signal if a tropical cyclone approaches within 800 kilometres (500 mi) of Hong Kong and poses a threat of deteriorating conditions in Hong Kong.
The signals are represented as a set of numbers and symbols. Previously lights were also used at night.
The Hong Kong Observatory began issuing warnings for tropical cyclones in 1884, when it began to monitor and report news of tropical cyclones within the South China Sea, and the areas around Guam and Manila. The monitoring efforts later expanded to gathering information from various seafaring vessels. These works were done in conjunction with the Marine Department until 1886. At first, the monitoring and warning services were geared mainly towards seafarers, and not towards the residents of Hong Kong.
The warning system was numerical, consisting of symbols hoisted at various places in Victoria Harbour, in the form of drums, balls, and cones. At first, the signals only gave information as to the cardinal direction from which winds were coming. Revisions of the system in 1904 added alerts as to ordinal wind direction. Until 1917, there were two sets of warning signals, one set with black symbols, and one with red. The black symbols indicated that the tropical cyclone in question was less than 300 miles (480 km) from Hong Kong, while the red symbols indicated a distance of over 300 miles (480 km).
The alert system was also supplemented by the firing of guns (later cannons and bombs which, being so much louder, were considered an improvement), which became relied upon for severe weather updates, as few residents paid attention to the visual warning system intended for seafarers. Intensity was indicated by number of shots, three being an indication of a very intense cyclone. This audible alert system ended in 1937, as residents began to rely on radio, newspapers, and notices at ferry piers for tropical cyclone information.
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