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Affected by frequent replenishments of the winter monsoon with spells of cloudy and rainy weather, December 2014 was cooler than normal. The mean temperature for the month was 16.3 degrees, 1.6 degrees below the normal figure of 17.9 degrees. The total duration of bright sunshine in the month was 115.3 hours, 33 per cent below the normal figure of 172.2 hours. The monthly total rainfall was 44.7 millimetres, about 67 per cent above the normal figure of 26.8 millimetres. The annual rainfall of 2014 was 2638.3 millimetres, about 10 per cent above the normal of 2398.5 millimetres.
After the passage of a cold front early on December 1, an intense winter monsoon swept through the coastal areas of Guangdong and brought appreciably cooler weather to Hong Kong early of the month. Cloudy conditions prevailed with some rain patches before the weather turned generally fine following the dissipation of clouds on December 8 and 9.
As Tropical Storm Hagupit made its way across the South China Sea, a broad band of clouds extended over the coastal waters of Guangdong and cloudy skies returned on December 10 to 12 with a few rain patches. Coupled with the arrival of a surge of the winter monsoon, the weather turned colder as temperatures fell progressively. As a dry continental air mass reached the south China coastal areas, the weather became sunny on December 13 and 14. Despite a cloudy day on December 15, further replenishments of the winter monsoon in the next few days brought even colder and drier air to Hong Kong. The relative humidity plunged below 30 per cent on December 17 and temperatures fell to a minimum of 10.7 degrees, the lowest of the month, before midnight on December 19 as another cloud band moved in from the northern part of the South China Sea and brought significant rain to the territory.
The ebb and flow between dry and moist air masses across the south China coast continued in the latter part of the month. Following the fine and dry weather on December 20 to 22, the return of a moist and milder air mass brought the clouds and rain patches back in the next five days. The rain patches lasted until the morning of December 28 before the arrival of a surge of the winter monsoon later that day which brought drier conditions to Hong Kong. Following a cold morning on December 29, the weather remained generally fine, dry and cool towards the end of the month.
Two tropical cyclones occurred 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. Monthly meteorological figures and departures from normal for December are tabulated in Table 2.
Ends/Monday, January 5, 2015
Issued at HKT 17:58
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