A large-scale weather phenomenon associated with high pressure, light winds and clear skies.
In an anticyclone (also referred to as a high) the winds tend to be light and blow in a clockwise direction. Also the air is descending, which inhibits the formation of cloud. The light winds and clear skies can lead to overnight fog or frost. If an anticyclone persists over northern Europe in winter, then much of the British Isles can be affected by very cold east winds from Siberia. However, in summer an anticyclone in the vicinity of the British Isles often brings fine, warm weather.
UKCP09 provides a commentary about potential future changes in anticyclones over the UK. An overview is provided in Section 5.9 of the Briefing report, with further details in Annex 6 of the UKCP09 Climate change projections report. Anticyclones are also discussed, in terms of assessing how well HadRM3 (the regional climate model, RCM, used in UKCP09) simulates large-scale atmospheric features, in Annex 3.4.2.
Information about past anticyclones in the UK is available from the UKCP09 Extremes atlas.