GENEVA, Feb. 23 (Xinhua) -- The World Meteorological Organization (WMO) warned on Friday of an unusually extended cold spell in much of Europe before the end of the Northern hemisphere winter, couple with exceptionally high temperatures in the Arctic.
Because of a recent meteorological event called a Sudden Stratospheric Warming Event high up in the Stratosphere, about 30 km over the North Pole, "a period with significantly below-normal temperatures (cold spell) at least for this and the next two to three weeks is expected for most of Europe (from Spain to Greece and from Ireland to Russia)," said WMO's Regional Climate Center for Climate Monitoring.
The warming results from a breakdown of the usual high-altitude westerly winds and often leads to cold easterly winds coming from Siberia which influence temperatures in Europe.
The stratospheric warming event led to a split in the polar vortex, which is an area of low pressure in the upper atmosphere, with swirling westerly winds circulating around it. Typically, those winds are strong enough to keep the coldest air in the Arctic during the winter.
Such an event is expected to bring coldest days for the week beginning Feb. 26, with weekly temperature anomalies below minus 10 degrees Celsius in western European Russia, Belarus, Ukraine and Poland.
Weekly temperature anomalies below minus 6 degrees Celsius are expected in Central Europe, northern Italy, the Balkans and the Baltic States. The weekly anomalies for southern, western and northern Europe are forecasted with minus 3 to minus 6 degrees Celsius, the WMO said.
Daily minimum temperatures are expected to be below 0 degree Celsius even in the south. This cold period with surface frost could freeze the developing crops and fruits and could be a risk of life for vulnerable people exposed to the cold, the UN climate agency warned, adding that the late cold spell is unusual but not exceptional. In general, cold waves are becoming more infrequent.
By contrast, parts of the Arctic have witnessed exceptionally high temperatures. The temperature at Cape Morris Jesup weather station at the very top of Greenland, at one of the closest points of any land mass to the North Pole, has risen above the freezing mark on several occasions since Feb. 16.
The WMO concluded that the warmth over the Arctic Ocean appears to result partly from a pattern of atmospheric circulation bringing in southerly air, and partly from the release of heat into the atmosphere from open water areas.
