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According to the World Meteorological Organization, the year 2010 is almost certain to rank among the top three warmest years globally since the beginning of instrumental climate records in 1850. In Hong Kong, 2010 was characterised by irregular variations in monthly temperature and rainfall, though annual figures were close to normal.
The year started off with three notably warm months with monthly mean temperatures 0.7 to 1.6 degree above normal. This anomaly was mostly offset by the well below normal monthly mean temperatures in April and June, the former due to frequent passage of late season cold fronts and the latter due to gloomy weather. With insignificant anomalies of monthly mean temperatures in the second half of the year, the annual mean temperature in 2010 ended up at 23.2 degrees, close to the normal figure of 23.1 degrees. During the year, there were 13 very hot days (daily maximum temperature at 33.0 degrees or above) and 21 cold days (daily minimum temperature at 12.0 degrees or below), three days and two days more than normal respectively.
Despite a record breaking daily rainfall of 94.1 millimetres for February, the first half of year 2010 was relatively dry with the total rainfall about 16% below normal. However, the two heavy rain episodes which necessitated the issuance of the Black Rainstorm Warning in July and the torrential rainfall due to the passage of two tropical cyclones, namely Lionrock and Fanapi in September, pushed the annual rainfall up to 2 371.5 millimetres - close to the normal figure of 2 382.7 millimetres.
A total of 18 tropical cyclones occurred over the western North Pacific and the South China Sea in 2010, considerably less than the normal figure of around 30 tropical cyclones a year. Super Typhoon Megi was the most intense tropical cyclone of the year, and was the only tropical cyclone that reached super typhoon intensity (maximum 10-minute wind speed of 185 kilometres per hour or above near the centre) in the region. In Hong Kong, five tropical cyclones necessitated the issuance of local tropical cyclone warning signals, slightly less than the annual average of six to seven. The typhoon season started later than normal on July 15 when Typhoon Conson came within 800 kilometres of Hong Kong and the Standby Signal No. 1 was issued. Typhoon Chanthu, Severe Typhoon Fanapi and Super Typhoon Megi necessitated the issuance of the Strong Wind Signal No. 3 during their passages from July to October.
As for individual months, January was 0.7 degree milder than usual. 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 cold snap during the Chinese New Year period was more than counter-balanced by a persistently warm and humid maritime airstream towards the end of the month, making February wetter and 1.6 degree milder than usual.
It was mild and dry with plenty of sunshine in March. The northeast monsoon carried sand and dust originated from sandstorms over northern China down the Taiwan Strait, reaching the coast of Guangdong on March 21, and resulting in rather low visibility in Hong Kong on March 21 and 22.
Due to the frequent passage of cold fronts, April was 1.5 degree cooler than usual.
Rainfall over the territory was highly uneven in May. The total rainfall recorded at the Hong Kong Observatory Headquarters in the month was only 176.6 millimetres, about 54% of the normal figure of 329.5 millimetres, whereas over 300 millimetres of rainfall were recorded in the eastern part of the New Territories and western Lantau.
June was gloomier than usual. The total bright sunshine duration was only 58% of the normal figure. As a result, June was 0.8 degree cooler than usual.
July was hotter than usual with eight very hot days (daily maximum temperature of 33.0 degrees or above) in the month. Two heavy rain episodes which necessitated the issuance of the Black Rainstorm Warning on July 22 and 28 respectively made the month wetter than usual. Waterspouts associated with unstable weather were reported on July 22 and 27.
Dominated by a relatively strong Pacific ridge of high pressure, August was sunnier and drier than usual.
September was the wettest month of the year, with monthly rainfall of 583.1 millimetres, more than double the normal figure of 287.5 millimetres. Under severe thundery activities, 13 102 strokes of cloud-to-ground lightning were registered in Hong Kong during the hour just after midnight on September 9, the highest hourly reading since records began in 2005.
Due to the dominance of an intense northeast monsoon over southern China in the last six days of the month, October was cooler than usual.
With prevalence of dry northeast monsoon, there was ample sunshine in November.
Despite several cold episodes in the month, December was slightly milder than normal with abundant sunshine.
Attachment 1 and 2 show respectively the monthly mean temperature anomalies and total rainfall anomalies in 2010.
Ends/Friday, January 7, 2011
Issued at HKT 19:48
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