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The first month of 2010 was milder than usual. The first half of January was cooler than normal while the weather became significantly milder than usual in the second half, resulting in a mean temperature of 16.8 degrees for the whole month which was 0.7 degrees above normal. There were only four cold days (daily minimum temperature at 12.0 degrees or below) in the month, the least for January since 2001. The month was also cloudier than normal. The mean cloud amount for the month was 73%, about 13% above normal. The total bright sunshine duration was 108.7 hours, about 23% below the normal figure of 141.7 hours.
Under the influence of an easterly airstream, it was generally cloudy with a few light rain patches for the first three days of the month. A ridge of high pressure established over southeastern China and brought sunny periods to Hong Kong on January 4.
An easterly airstream affected the coast of Guangdong and brought cloudy and cooler conditions to the territory on January 5. A cold front crossed the coastal areas of Guangdong on January 6, bringing a few rain patches and a significant drop in temperature during the day over the territory. The weather remained cloudy and cold for the next two days. With moderation of the winter monsoon, the temperatures rose gradually and there were sunny periods on January 9 and 10.
The winter monsoon over the south China coastal areas strengthened on January 11. Local weather turned overcast with rain and temperatures dropped gradually that day. Clouds started to thin the next morning but cold weather persisted over the territory on January 12 and 13. The temperatures recorded at the Hong Kong Observatory fell to a minimum of 9.8 degrees on January 13, the lowest of the month. The weather remained fine and dry for the ensuing five days.
A mild easterly airstream affecting the coastal areas of Guangdong brought mild weather with some sunny periods for Hong Kong from January 19 to 21. Meanwhile, a cold front over southern China moved southward gradually on January 21 and crossed the coastal areas of Guangdong the next morning. The northeast monsoon behind the cold front brought cooler weather with some light rain patches to Hong Kong from January 22 to 24. Weather improved the next day with some sunny intervals.
A humid maritime airstream over the coastal areas of Guangdong brought cloudy and misty weather with some light rain patches to the territory from January 26 to 28. Affected by a fresh easterly airstream, it was slightly cooler on January 29. With moderation of the easterly winds, local weather became mainly fine apart from some mist patches on January 30. With abundant sunshine, the temperature rose to 24.5 degrees on the last day of the month, the highest of the month.
There was no tropical cyclone 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 in January are tabulated in Table 2.
Ends/Tuesday, February 2, 2010
Issued at HKT 18:46
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