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The weather of May 2016 was warmer with less rain than usual. The monthly mean temperature was 26.7 degrees, 0.8 degrees above the normal figure of 25.9 degrees. Despite several rainstorms in the month, the monthly total rainfall was only 233.6 millimetres, about 23 per cent below the normal figure of 304.7 millimetres. Having said that, the accumulated rainfall of 885.4 millimetres in the first five months of the year was about 38 per cent more than the normal figure of 640.8 millimetres for the same period.
Under the influence of an easterly airstream, the weather in Hong Kong was slightly cooler with a few showers on May 1. The minimum temperature of 20.4 degrees recorded at the Hong Kong Observatory that morning was the lowest of the month. With the easterly airstream gradually replaced by a warm and humid maritime airstream, local weather became warm and foggy with a few showers on May 2. Affected by a trough of low pressure over the coastal areas of Guangdong, there were showers and thunderstorms in the next two days. The showers were particularly heavy in the evening on May 3, with more than 30 millimetres of rainfall recorded over many places in the territory.
Dominated by a southerly airstream, it was hot with sunny periods in Hong Kong from May 5 to 9. An area of intense rain and thunderstorms associated with a trough of low pressure swept across the Pearl River estuary on May 10. More than 70 millimetres of rainfall were generally recorded in Hong Kong, with rainfall over Sha Tin and Sai Kung exceeding 150 millimetres. The Red Rainstorm Warning Signal was issued twice that morning.
After mainly fine and relatively dry weather on May 11, it became generally cloudy with isolated showers over the next three days as a fresh easterly airstream prevailed over the coast of Guangdong. With the moderation of the easterly airstream, the weather turned mostly fine on May 15. Despite some light rains due to the passage of a cold front that night, the weather remained fine the next day with slightly cooler temperatures as a relatively dry northerly airstream reached the coast of Guangdong. The freshening of easterly winds once again brought cloudy weather and some rain patches to Hong Kong on May 17 to 19.
Affected by a trough of low pressure over the coast of Guangdong, local weather deteriorated with heavy showers and squally thunderstorms on May 20 and 21. The rainstorm episode in the early morning on May 21 brought more than 70 millimetres of rainfall to many places. Over 200 millimetres of rainfall was recorded in Sai Kung and a few landslides were reported. As the trough weakened, local weather improved and it was generally fine and hot on May 22 to 25.
The weather became windy and showery in Hong Kong as a monsoon depression over the northern part of the South China Sea developed into a tropical depression in the night on May 26, and the Tropical Cyclone Warning Signal was issued for the first time this year. The tropical depression landed over the coast of western Guangdong near Yangjiang the next day, bringing strong winds to the territory. After the tropical depression landed, local weather became even more unsettled with heavy showers and thunderstorms on May 28 under the influence of an active southwest monsoon. More than 40 millimetres of rainfall were generally recorded over the territory, with rainfall in Kwai Tsing and Tsuen Wan exceeding 100 millimetres.
With the moderation of the southwest monsoon, the weather became hot with sunny periods and a few showers towards the end of the month. Daytime temperature at the Hong Kong Observatory soared to 32.1 degrees on May 30, the highest of the month.
One tropical cyclone occurred over the South China Sea and the western North Pacific in the month.
Details of issuance and cancellation of various warnings/signals in the month are summarised in Table 1. Monthly meteorological figures and departures from normal for May are tabulated in Table 2.
Ends/Friday, June 3, 2016
Issued at HKT 16:36
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