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April was drier and cooler than usual, with the mean temperature of 22 degrees being 0.5 degrees below the normal figure of 22.5 degrees. The total rainfall in the month was 108.7 millimetres, about 42% below the normal figure of 188.5 millimetres. The accumulated rainfall since January 1 was 230.5 millimetres, about 32% below the normal figure of 337.1 millimetres for the same period.
Under the influence of a dry northeast monsoon, it was dry with sunny periods for the first two days of the month. With winds strengthening from the east, local weather became cloudy with some rain patches on April 3. With the easterly winds moderating, sunny intervals developed on April 4 and 5.
A cold front formed over the northern part of southern China on April 4 and moved across the south China coastal areas in the afternoon of April 5. Locally, the weather became cooler and rainy on April 6 and 7. Affected by a dry easterly airstream over the coastal areas of southern China, it was mainly fine for the next four days.
A trough of low pressure over the south China coastal areas brought showery weather to Hong Kong from April 12 to 16. With the trough of low pressure dissipating, local weather turned mainly fine on April 17. A fresh to strong easterly airstream over southern China brought windy and rainy weather to the territory for the next two days. With winds subsiding gradually, local weather became sunny and hot during the day on April 20. The temperature at the Hong Kong Observatory rose to 30.1 degrees on that day, the highest of the month.
Affected by another fresh to strong easterly airstream over the south China coastal areas, it was windy and rainy in Hong Kong from April 21 to 23. With moderation of the easterly airstream, it was cloudy and misty on April 24. An active trough of low pressure formed over central China on April 24 and crossed the coast of Guangdong the next day, bringing heavy rain and squally thunderstorms to Hong Kong on the morning of April 25.
Under the influence of the northeast monsoon, it was cooler and rainy in Hong Kong on April 26. A dry easterly airstream associated with a ridge of high pressure over the southeastern coast of China brought mainly fine and dry weather to Hong Kong for the last four days of the month.
There was no tropical cyclone 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 1.1. Monthly meteorological figures and departures from normal for April are tabulated in Table 1.2.
Ends/Tuesday, May 5, 2009
Issued at HKT 18:32
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