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THE ENVIRONMENT
ground. Afternoon temperatures are usually about 5°C higher than those during the coldest part of the night.
Mean relative humidity exceeds 80 per cent from mid-February until early September. November is the least humid month with a mean relative humidity of 69 per cent. The daily average of bright sunshine ranges from three hours in March to more than seven hours in mid-July and late October.
Gales caused by tropical cyclones may be expected from May to November but are most likely from July to September. The passage of these cyclones several times a year at varying distances from Hong Kong brings spells of bad weather with strong winds and heavy rain. Gales are experienced once a year on average, and less fre- quently the centre of a mature typhoon passes sufficiently close to Hong Kong to produce winds of hurricane force, endangering life and property.
The Year's Weather
Although exceptionally dry conditions prevailed during the first nine months of the year and created a serious water shortage, heavy downpours associated with typhoons Carmen and Elaine in October brought a welcome relief to the drought and brought an end to the water supply restrictions imposed in September. The accumulated rainfall was more than 30 per cent below average on September 30 but rose to seven per cent above normal by the end of the year.
Out of a total of 34 tropical cyclones which formed in the western North Pacific and the South China Sea during the year, an unprecedented number of 11 affected Hong Kong and necessitated the hoisting of tropical cyclone warning signals. It was also the first time in the history of the Royal Observatory that four tropical cyclones affected the territory during October and one passed close enough to cause strong winds in December.
The first three months of the year were much drier and sunnier than usual and fire danger warnings were in force on 44 days. The first tropical cyclone reported in the year, severe tropical storm Wanda, formed to the east of the southern Philip- pines on January 10. It moved northeastwards and dissipated over the cold waters east of Luzon on January 14. Two cold spells were experienced during February when frost and ice formation were reported on high ground and in the New Terri- tories. The air temperature fell to 4.2°C at the Royal Observatory early on February 26, which was the lowest temperature recorded in the year. The minimum temperature recorded on the same morning at Tai Mo Shan and Tate's Cairn were -6.5°C and -2.2°C respectively. On February 23, widespread fog and low visibility associated with a moist airstream from the Pacific caused 23 aircraft to divert from Hong Kong International Airport. The strong monsoon signal was hoisted three times in February and once in March. A tropical storm, Amy, developed near the Caroline Islands on March 14. It moved westwards at first and then recurved northeastwards, dissipating over the Pacific to the southeast of Japan on March 19.
Violent thunderstorms associated with cold surges resulted in 231.1 mm of rainfall in April, making it the first month since September 1973 with above average
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