According to the World Meteorological Organisation, the year 2009 would likely rank among the top 10 hottest years globally on record.The weather in Hong Kong was exceptionally warm in 2009 with an annual mean temperature of 23.5 degrees the 9th highest on record and the same as 1991 and 2006 (see attached table).The average temperature in February reached a record high of 20.5 degrees, 4.2 degrees above the climatological normal.Prolonged hot summer weatherconditions extended into late September with 30 days having daily maximum temperatures of 33 degrees or above, the highest since 1963.The Very Hot Weather Warning was in effect on 40 days, the highest number since the warning started operation in 2000.The year 2009 was also drier than usual with the annual rainfall of 2182.3 millimetres being about 8% below normal.
A total of 30 tropical cyclones occurred over the western North Pacific and the South China Sea in 2009. Five tropical cyclones attained super typhoon intensity (maximum 10-minute wind speed of 185 km/h or above near the centre) over the western North Pacific.However, none of these directly affected Hong Kong.Eight tropical cyclones necessitated local tropical cyclone warning signals this year, slightly more than the annual average of six to seven.Typhoon Molave passed about 40 km north-northeast of the Hong Kong Observatory Headquarters in July and necessitated the Increasing Gale or Storm Signal No 9, the highest signal issued in the year. Two other tropical cyclones led to Gale or Storm Signal No 8 – namely Severe Tropical Storm Goni in August and Typhoon Koppu in September.
For individual months of 2009, January was sunnier and drier than usual.The total bright sunshine duration for the month was 226.5 hours, about 60 % above normal.
Due to a lack of northerly surges, it was unusually warm in February.It was the warmest February since records began in 1884. The temperature of 28.3 degrees recorded on February 25 was the highest on record for February.The month was also sunnier than normal.
March was wetter and warmer than usual.
The weather in April, May and June was drier than normal.
July was warmer than usual.
Under the influence of a stronger than normal sub-tropical ridge, the weather was much hotter than usual in August, September and October.
The mean temperatures of 29.4 degrees for August, 28.8 degrees for September and 26.2 degrees for October were 1.0, 1.2 and 0.9 degrees higher than their respective climatological normals.The mean minimum temperatures of 27.7 degrees for August and 26.9 degrees for September were the highest for the respective months on record.It was also wetter than usual in September.The total rainfall of 486.3 millimetres in the month was about 69% above normal.
The weather was cooler than usual in November.The temperature fell to 10.5 degrees on November 17, the earliest day for winter since 1981 when the minimum temperature was 12.0 degrees or below.The first Cold Weather Warning issued on November 16 was also the earliest since the warning started operation in 1999.
December was cooler and wetter than usual.
Attached figure shows the monthly mean temperature in 2009 compared with the climatological normal values.