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THE ENVIRONMENT
hourly rainfall of 82.1 mm recorded at 3 pm on the same day also set a new record for August. Typhoon Hope, together with a tropical depression near Xisha (the Paracels), brought the month's total rainfall to 706.9 mm which is 286.7 mm above average. The month was also cloudier and less sunny than usual. The total duration of bright sunshine was 138.2 hours which ranks as the fourth lowest on record for August. Widespread thunder- storms occurred for several hours around noon on August 9.
Heavy rain associated with Severe Tropical Storm Mac brought September's total rain- fall to 506.3 mm, which is 53 per cent above average. The month was less sunny and slightly cooler than normal. There have been very few occasions when two tropical cyclones have been centred within 400 nautical miles of Hong Kong at the same time. On September 19 the stand-by signal, No. 1, was hoisted for Tropical Storm Nancy, but as Nancy moved away westwards across Hainan Dao (Hainan Island) Severe Tropical Storm Mac ap- proached from the southeast and the stand-by signal remained hoisted. Mac passed over western Lantau Island during the night of September 23 and brought gales and heavy rain to Hong Kong. Mac left one person dead and 67 people injured. Many roads were flooded and several minor landslips occurred.
October was the driest October on record with no rainfall registered at the Royal Observa- tory. It was also the sunniest, least humid and least cloudy October on record. There were no significant changes in the daily weather: every day was fine, sunny and dry. More than 2,000 fires occurred during the month. About 400 of these were hill fires which destroyed or damaged more than 200,000 trees and 1,600 hectares of vegetation.
November was dry and windy. The strong monsoon signal was hoisted on five occasions and displayed for a total duration of 108 hours and 10 minutes. Both figures are the highest on record for November since the introduction of this signal in 1950. The month was also less sunny and cooler than usual. There were more than 1,600 fires reported in the month. About 200 of these were hill fires which destroyed more than 300,000 trees and 1,105 hectares of vegetation. Strong to gale force winds blew over Hong Kong from the evening of November 17 until the morning of November 19. Due to the very dry conditions, a single fire which broke out on the morning of November 18 in the Tai Lam Chung area raged for 30 hours and destroyed some 265,000 trees and 500 hectares of vegetation.
December was mild, sunny and dry. There was just one day with measurable rain recorded at the Royal Observatory: the total rainfall recorded was only 0.2 mm which is the seventh lowest amount on record for December. The mean temperature of 18.6°C was 1.1°C higher than normal, while the sunshine duration of 230.4 hours was 58.5 hours more than normal.
The Royal Observatory
The Royal Observatory is concerned with matters relating to meteorology and geophysics. Apart from the World War years of 1940-6, meteorological observations have been made at its Tsim Sha Tsui headquarters since 1884. The most important function of the observa- tory is the provision of weather forecasting services and tropical cyclone warnings to the public and international shipping and aviation.
Routine weather forecasts for the public are prepared in the Central Forecasting Office and broadcast over radio and television at frequent intervals every day. Warnings of hazardous conditions such as thunderstorms, heavy rain, fire danger or low temperatures are issued whenever necessary. The Central Forecasting Office is also responsible for issuing weather forecasts twice daily for shipping covering areas in the China Seas. In April, 1979, a broadcast of comprehensive weather information for the south China coastal waters, in both English and Chinese, was introduced in response to the needs of fishermen, yachts-