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Last month (April) was drier and cooler than usual. The mean temperature of 21.8 degrees was 0.4 degree below normal for April. The monthly rainfall of 125.5 millimetres was about 22% below normal. The accumulated rainfall in the first four months of the year amounted to 189.6 millimetres, about 37% below the normal figure of 299.8 millimetres for the same period.
Under the influence of a maritime airstream, it was warm with sunny periods on the first day of April. A cold front moved across the coast of Guangdong on April 2, bringing squally showers and thunderstorms to the territory. It was rather cool with rain on April 3. The temperature dropped further to 12.3 degrees on the morning of April 4, the lowest in the month. The weather stayed cloudy with a few rain patches in the following four days.
The weather improved with plenty of sunshine on April 9. It turned rainy again the next day when a broad band of cloud covered southern China. With a ridge of high pressure establishing over southeastern China, it became mainly fine on April 11 and the following two days. A maritime airstream set in on April 14 and brought a few light rain patches in the morning. It was warm and sunny on the next two days. The temperature rose to 29.4 degrees on April 16, the highest in the month. The weather became unstable on April 17 when a cold front reached the south China coast. A squall line swept across Hong Kong that night, bringing severe gusts and heavy showers. Peak gusts of more than 100 kilometres per hour were recorded at some places of the territory. In Admiralty, three people were injured when a sign board collapsed in gusty winds.
Hong Kong came under the influence of dry northerlies on April 18. It was fine, clear and very dry with relative humidity dropping below 30%. The weather remained generally fine in the ensuing two days.
A moist maritime airstream brought misty weather to Hong Kong on April 21, and visibility at Hong Kong International Airport fell below 3000 metres. It was cloudy with a few showers on April 22.
Under the influence of a trough of low pressure over southern China, there were heavy rain and squally thunderstorms on April 23 and 24. The Red Rainstorm Warning Signal was issued for the first time this year on April 24. More than 70 millimetres of rainfall were recorded over Hong Kong Island, Tseung Kwan O, Shatin and the northern part of the New Territories. The weather remained cloudy with some rain patches on April 25.
Clouds thinned out with plenty of sunshine during the day on April 26. Mainly fine weather continued in the next two days. The weather became cloudy with rain patches on the last two days of the month when local winds freshening from the east.
Only one tropical cyclone occurred in the western North Pacific in the month.
Details of the issuance and cancellation of various warnings/signals in the month are summarised in Table 1. Monthly meteorological figures and departures from normal of April are shown in Table 2.
Ends/Thursday, May 3, 2007
Issued at HKT 16:13
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