ENG-1974 — Page 256

THE ENVIRONMENT

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rainfall. However, the heavy rains were confined to three days, and the month was sunnier than usual. The strong monsoon signal was hoisted on April 1-2 when a strong northerly surge affected Hong Kong. Tropical storm Babe formed near the Caroline Islands on April 26. It moved northwards and became extratropical six days later.

Dry conditions returned in May and the rainfall for the month was more than 30 per cent below average. More than half of the month's rain fell on May 2 when an active trough of low pressure passed through Hong Kong from the north. A second trough arrived on May 30 and heavy thunderstorms associated with it resulted in the death of three campers on Lantau Island.

Although there were only five days in June with no rainfall recorded at the Royal Observatory, the total rainfall for the month was still 20 per cent below average. The month was cloudy and a late surge of the winter monsoon on June 5-6 neces- sitated the hoisting of the strong monsoon signal for 21 hours. Four tropical cyclones were observed during the month and two affected Hong Kong. A tropical depression which formed over the South China Sea on June 6 caused periods of strong winds in Hong Kong on June 6-7 while typhoon Dinah, which developed over the Pacific about 50 miles off Yap, brought strong to gale force easterlies on June 12. However, both tropical cyclones were relatively dry and were associated with little rain in Hong Kong.

July was warm and sunny with below average rainfall and the mean relative humidity of 78 per cent was the third lowest on record for the month. Four-tropical cyclones formed in the western North Pacific during the month but only one, typhoon Ivy, brought gales to Hong Kong.

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August was even less humid than July and the mean relative humidity of 76 per cent was the lowest ever recorded for the month. It was also much warmer than usual and the mean maximum temperature of the month, 32°C, was the third highest on record. On August 20, under the influence of the southwest monsoon the air tem- perature rose to 34.3°C—the maximum recorded in the year. Slightly cooler condi- tions were experienced after the arrival of an early surge of the winter monsoon on August 25 and fire danger warnings were in force on August 25-27. Although seven tropical cyclones were reported during the month, none came sufficiently close to affect Hong Kong. This was the first occasion since 1969 when no signals were hoisted in August.

Dry and warm weather continued in September with only 47 per cent of the average rainfall recorded during the month. The general deficiency in rain during the previous months created a serious problem of water shortage and restrictions on water supply were imposed on September 25. Out of the five tropical cyclones reported during the month, two, tropical storm Trix and severe tropical storm Wendy, necessitated the hoisting of tropical cyclone warning signals in Hong Kong.

Dry conditions came to an end in October when prolonged heavy rain associated with tropical cyclones brought more than seven times the average amount of rainfall for the month to Hong Kong. The monthly total amounted to 718.4 mm which was