Last Year’s Weather Exceptionally Mild and Changeable

Armagh Observatory reports that although the extremely cold weather in late November and December 2010 was not repeated during 2011, the weather at Armagh last year was exceptionally mild and changeable.

January 2011 was the fourth sunniest January on record and the sunniest January at Armagh since 1959. April was also very sunny, being the eleventh sunniest April at Armagh since 1881 when sunshine records began at the Observatory. April 2011 was also a very mild month with a mean monthly temperature of 11.7°C, making it the warmest April at Armagh in 215 years, that is, since such records began in 1795. Spring 2011 (March, April, May), with an average temperature of 10.0°C, was the warmest spring on record at Armagh. The previous warmest spring (with a nearly identical average temperature) was that of 1945.

In contrast, although Autumn 2011 (September, October, November) was exceptionally mild, it was characterized by largely dull and very wet weather. Autumn 2011 was the dullest and wettest since 1989 and 1838, respectively. October 2011, with approximately 183 mm of precipitation, was the second wettest October since 1870 (c.194 mm). However, with an average daily temperature of 11.7°C, Autumn 2011 was also the warmest autumn at Armagh on record, that is, since 1795.

September 2011 was nearly a degree warmer than the recent (1981–2010) 30-year average; October was a little more than a degree warmer than average; and November, with an average monthly temperature of 9.4°C, was nearly 2.4 degrees warmer than the recent 30-year average — and the second warmest November on record. The three warmest Novembers are now 1994 (9.6°C), 2011 (9.4°C) and 1899 (9.3°C).

Christmas Day, with a maximum temperature of 13.5°C, was the warmest Christmas Day on record (i.e. since records of the maximum daily temperature, Tmax, began in 1843, and 2011 December 31 produced the third warmest New Year’s Eve on record (Tmax = 12.1°C).

Taking 2011 as a whole, both spring and autumn were exceptionally mild, and this helped to make 2011 the sixth warmest year on record (average temperature 10.29°C) despite a relatively cool summer (average temperature 14.1°C, compared with 15.0°C for the recent 30-year average). However, total precipitation and the total number of hours of strong sunshine were close to average.

These data refer to observations at Armagh Observatory, which has been recording the weather at Armagh since 1795.

FOR FURTHER INFORMATION PLEASE CONTACT: John McFarland at the Armagh Observatory, College Hill, Armagh, BT61 9DG. Tel.: 028-3752-2928; FAX: 028-3752-7174; jmfat signarm.ac.uk; URL: climate.arm.ac.uk.

Last Revised: 2011 January 12th