COLD SPELLS

Western Europe has a maritime climate, dominated by westerly circulations. Occasionally, circulation anomalies are produced that result in a temporal reversal of the wind direction. If the reversal persists, this phenomenon is referred to as atmospheric blocking. In winter, the anomalous circulation transports cold air originating from Siberia in the direction of Western Europe. A cold spell can result if the atmospheric circulation persists for many days. A good example is the recent 2-week cold spell that started at the end of January 2012. The image below gives an indication of the scale of cold-spell (grey-ish colors imply more than 10 degrees below climatology, blue contours denote sea-level pressure).