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Due to the frequent replenishments of the winter monsoon, the monthly mean temperature of 13.7 degrees for the first month of 2011 was 2.4 degrees below normal, making it the coldest January since 1977. There were 14 cold days (daily minimum temperature at 12 degrees or below) in the month, doubling the normal figure of seven days. The temperature did not rise to 20 degrees or above during the month, which only occurred once for January on record - in 1918. The month was also drier than usual with only 5.4 millimetres of rainfall, about 22% of the normal figure.
Under the influence of a dry northeast monsoon, the weather was fine and dry on the first day of the month. A strong easterly airstream affected the coastal areas of Guangdong and brought windy and cloudy weather to Hong Kong on January 2. It remained cloudy with some light rain patches for the ensuing three days. With the arrival of an intense winter monsoon on January 6, a cold spell began to affect Hong Kong lasting until January 13. There were light rain patches on January 6 and 7. Affected by a dry northerly airstream, the weather turned fine and dry but remained cold in the morning from January 8 to 10. An extensive cloud band over southeastern China brought some rain to the territory from January 11 to 13. The temperature fell to a minimum of 7.2 degrees at the Hong Kong Observatory on the morning of January 12, the lowest of the month.
With a moderation of the winter monsoon and abundant sunshine, the weather turned mild in Hong Kong on January 14. The temperature at the Hong Kong Observatory rose to a maximum of 19.4 degrees, the highest of the month. Cold and windy weather resumed the next day when another surge of the winter monsoon reached the south China coast. It remained cold and dry on January 16 and 17.
The local weather was mainly fine on January 18 and 19. It turned cloudy with some haze on January 20. With a replenishment of the winter monsoon, it became cold again in the morning with fine and dry weather on the next day. It remained generally fine with some haze from January 22 to 28. Another replenishment of the winter monsoon reached the south China coast later on January 28, bringing cold and dry weather to Hong Kong for the last three days of the month.
There was no tropical cyclone over the South China Sea and the western North Pacific during 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 January are tabulated in Table 2.
Ends/Tuesday, February 1, 2011
Issued at HKT 19:33
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