264
THE ENVIRONMENT
However, the air temperature was near normal and the daily minimum temperature fell below 10°C only once, on January 10, when a minimum of 8.8°C was recorded. The winter monsoon was less active in January and the strong monsoon signal was hoisted on only one occasion.
Abnormal, changeable and unsettled weather conditions were experienced in February with a number of meteorological elements resulting in exceptional statistics. The earliest occurrence of hail was recorded, and the mean atmospheric pressure for the month reached a record low. The total rainfall of 218.8 mm and the total number of rain days, 25, were the second highest readings on record for February. A flood warning was issued for the first time in the year. The unsettled weather in the early part of the month was due to the influence of an active trough of low pressure which also affected broad areas of southern China. During the rest of the month there were frequent surges of cold air, causing cloudy weather and rain at times. As a result of the adverse weather, 10 aircraft were diverted from Hong Kong.
March was cloudier and cooler than usual. The mean temperature of 16.7°C was 1.8°C below normal. The slightly cooler weather was due to the continuing presence of a continental anticyclone. A surge of winter monsoon in mid-March caused the temperature to drop to a minimum of 10.6°C. Another surge at the end of the month brought squally thunderstorms and periods of heavy rain. Hailstorms causing considerable damage were reported in nearby districts in Guangdong Province.
April was wetter than usual with more than 30 mm of rainfall being recorded on six days. The total rainfall was almost twice the normal value of 139.4 mm. Marble-sized hailstones were reported in the urban area and in the New Territories on April 10. Hail was also reported in Canton and various parts of Guangdong Province. A continuous wet spell in the second week of April caused flooding and minor landslips. The month was also cooler than normal. The mean temperature was 1.6°C below the normal figure of 22.1°C.
May was warmer and drier than usual. The mean temperature of 26.8°C the sixth highest on record for May - was 0.9°C above normal. A spell of fine and sunny weather lasting 13 days was experienced in the first half of the month, and no measurable rainfall was recorded on 20 days. The total rainfall recorded for the month was only one-third of the normal amount.
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June was much cloudier than usual. The mean atmospheric pressure was the lowest on record for the month. Typhoon Hal came within 740 km of Hong Kong on June 22 and necessitated the hoisting of tropical cyclone warning signals for the first time in the year. Gale force winds were experienced offshore in Hong Kong from the northwest during the approach of Typhoon Hal. Squally thunderstorms and heavy showers occurred early on June 25 as Hal came within 110 kilometres of Hong Kong before moving inland. More than half of the total monthly rainfall was attributed to a downpour on June 25 and the situation warranted the issuance of a landslip warning. Land, sea and air traffic was disrupted and flooding and minor landslips occurred in various parts of the territory. At the airport, 11 flights were cancelled, 26 delayed, and one was diverted.
July was the third consecutive month with less than normal rainfall. The stand-by signal, No. 1, was hoisted on July 8 as a tropical depression over the South China Sea turned northwards and accelerated towards the South China coast to the east of Hong Kong. Over 200 mm of rainfall were recorded in Sha Tin when heavy showers and severe thunderstorms early on July 9 caused serious flooding and minor landslips in the region. The third report of hail in the year came on July 26 and this was associated with squally thunderstorms in an active southwest monsoon.