2015: A year of record-breaking high temperatures

     According to the World Meteorological Organization's preliminary assessment, 2015 is likely to be the warmest year globally since records began in 1850. Over the Arctic, the minimum sea ice extent in September 2015 was the fourth lowest on record. Moreover, notable extreme weather events wreaked havoc in many parts of the world in 2015 including heatwaves in India, southern Pakistan, northern Africa, South Africa, the Middle East, southern Australia and many parts of Europe, snow storms in Boston and Worcester of the United States, droughts in western North America, South Africa, Russia, southern Chile, Brazil and Indonesia, extreme rainfall and flooding in southern United States, Mexico, southeastern Europe, the United Kingdom, Pakistan, China and Argentina, and torrential rain induced by tropical cyclones in the southern United States, Myanmar, Japan and Yemen.

     Over the central and eastern equatorial Pacific, the El Niño episode started in May 2014 and continued into 2015. The sea surface temperature warmed progressively and significantly during the course of the year, developing into a strong event by late summer and setting a record for the longest episode since 1950.

     Against a background of global warming, 2015 also emerged as the warmest year in Hong Kong on record with an annual mean temperature of 24.2 degrees, 0.9 degrees above the 1981-2010 normal (Note 1) (and 1.2 degrees above the 1961-1990 normal). The mean temperatures for June, November, summer (June to August) and autumn (September to November) in 2015 all ranked the highest since records began in 1884.

     For extreme temperatures, there were 28 Very Hot Days (Note 2) and 37 Hot Nights (Note 3) in Hong Kong in 2015, ranking the fifth highest and the highest on record respectively. The number of Cold Days (Note 4) in the year was only seven days, 10 days below the 1981-2010 normal and one of the lowest on record. The maximum temperature recorded at the Hong Kong Observatory reached a record high of 36.3 degrees on August 8, while the minimum temperature of 10.3 degrees recorded during the year on January 14 was the second highest on record.

     The year 2015 was drier than normal in Hong Kong. The annual total rainfall was 1 874.5 millimetres, a deficit of 22 per cent compared to the 1981-2010 normal of 2 398.5 millimetres (and about 15 per cent below the 1961-1990 normal). The number of days with thunderstorms reported in Hong Kong was 37 days in 2015, close to the 1981-2010 normal. Affected by a trough of low pressure, torrential rain and intense thunderstorms in Hong Kong necessitated the issuance of the Black Rainstorm Warning on May 26.

     A total of 27 tropical cyclones occurred over the western North Pacific and the South China Sea in 2015, less than the long-term (1961-2010) average of around 30. There were 20 tropical cyclones reaching typhoon intensity or above (Note 5) during the year, more than the long-term average of about 15, and 13 of them reached super typhoon intensity (maximum 10-minute wind speed of 185 km/h or above near the centre), the highest since full records began in 1961. In Hong Kong, three tropical cyclones necessitated the issuance of local tropical cyclone warning signals, lower than the long-term average of about six in a year. The No. 8 Gale or Storm Signal was issued during the passage of Typhoon Linfa in July.

     Detailed description of the weather for individual months is available on the Monthly Weather Summary webpage:
www.hko.gov.hk/wxinfo/pastwx/mws.htm .

     A detailed version of the Year's Weather for 2015 with some significant weather events in Hong Kong is available at: www.hko.gov.hk/wxinfo/pastwx/ywx.htm .

Note 1: Climatological normals for the reference period of 1961-1990, 1971-2000 and 1981-2010 are available at www.weather.gov.hk/cis/normal_e.htm . Climatological normals of 1981-2010 are referenced in the text unless otherwise stated.

Note 2: "Very Hot Day" refers to the condition with the daily maximum temperature equal to or higher than 33.0 degrees.

Note 3: "Hot Night" refers to the condition with the daily minimum temperature equal to or higher than 28.0 degrees.

Note 4: "Cold Day" refers to the condition with the daily minimum temperature equal to or lower than 12.0 degrees.

Note 5: Information on the classification of Tropical Cyclones is available at www.hko.gov.hk/informtc/class.htm .

Ends/Thursday, January 7, 2016
Issued at HKT 17:41