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March 2012 was characterised by a distinctive transition from humid to dry weather. Resulting from the contests between the northeast monsoon and the maritime airstream over the south China coastal areas, the weather of the first half of the month in Hong Kong was gloomier, cooler and more humid than usual. In contrast, the second half of the month was generally fine, mild and dry under the prevalence of a continental airstream for most of the time. Overall, the mean temperature and relative humidity of the whole month were both near normal. The monthly rainfall was only 22.1 millimetres, about 27 per cent of the normal level.
Under the influence of a humid easterly airstream, the weather was cloudy with light rain patches and coastal fog on the first day in the month. With the clouds thinning out during the day, it was warm with sunny periods on March 2. The northeast monsoon reached the coast of Guangdong on March 3, bringing cloudy, foggy and slightly cooler weather to the territory on March 3 and 4. While remaining foggy, the weather became warm in the following two days as a maritime airstream prevailed over the coastal areas. Affected by another northeast monsoon over southern China, local weather became cooler with fog and rain patches from March 7 to 9. With the strengthening of the northeast monsoon, it turned cold amid mist and rain patches for the ensuing four days. The minimum temperature at the Observatory dropped to 11.4 degrees on March 12, the lowest of the month. With the northeast monsoon over southern China abating gradually, it was mainly cloudy with a few light rain patches on March 14 and 15.
Affected by a humid and mild maritime airstream over the coastal areas of Guangdong, it was mainly fine but foggy in the morning from March 16 to 18. The visibility in the eastern Harbour and at Waglan Island once fell below 100 metres in the morning on March 18. With plenty of sunshine, the temperature at the Observatory rose to a maximum of 28.8 degrees on the same day, the highest of the month.
The arrival of the northeast monsoon over the coast of Guangdong in the morning of March 19 brought some fog patches to Hong Kong. Affected by the associated fresh to strong easterly airstream, local weather was slightly cooler in the following three days.
A cold front moved across the coastal areas of Guangdong on March 23. Under the influence of the associated intense northeast monsoon, local temperature fell significantly in the afternoon on March 23 and the weather became rather cool and dry the next day. With the persistence of the continental airstream, the weather was generally fine and dry with the temperature rising from March 25 to 28. It was warm with sunny periods on March 29 and 30. A weak cold front moved across the coastal areas of Guangdong in the morning of March 31 and brought mainly cloudy weather to the territory.
Only one tropical cyclone occurred over the South China Sea and 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 March are tabulated in Table 2.
Ends/Tuesday, April 3, 2012
Issued at HKT 19:02
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