While most of the United States has snoozed through winter, Europe has battled deadly cold and heavy snow. Lately the weather seems to have shifted, with North America finally getting a taste of winter. But don't expect it to last, one expert said.
Europeans have been shivering under a blanket of cold air that has sent temperatures plummeting and snows drifting. Across the continent, hundreds have died from exposure to the cold. Temperatures in Belgrade, Serbia, have been the coldest in over 20 years, AccuWeather.com's senior meteorologist Jim Andrews told OurAmazingPlanet. The Danube River froze, snowfall blocked roads and stranded towns in central Italy and even Venice's famous canals froze, a rare feat.
Europe has seen brutal winters before. The Thames River in England stayed frozen with a thick layer of ice for nearly two months during the winter of 1683-84. During the frigid winter of 1812, Napoleon's Grande Armee was decimated by the extreme cold in Western Russia.
Keeping Europe frozen this winter is a climate pattern called a" Russian Winter." In this pattern, a strong Siberian anticyclone hovers over northern Russia and triggers intense cold and snow, according to a NASA statement. The cold occurred when the tight polar vortex that had bottled up the cold arctic air in the beginning of winter suddenly weakened.
"Cold air swept out of Siberia and invaded Europe and the Far East," said NASA climatologist Bill Patzert of the Jet Propulsion Laboratory.
The tight polar vortex is caused by the Arctic Oscillation (AO), a difference in pressure between the Arctic and lower latitudes. When the pressure difference is high — a positive phase — a whirlpool of air forms around the North Pole. Earlier this winter, that whirlpool was more forceful, corralling the cold air and keeping it nearer the pole, but it weakened and let the air escape into Europe.
The pressure difference eventually swung the other way a few weeks ago — a negative Arctic Oscillation — resulting in cold extremes on the other side of the planet, over North America. The cold snap brought record low temperatures to Florida.
So should people in North America expect a lingering cold to close out winter? Probably not, Patzert told OurAmazingPlanet, as the negative Arctic Oscillation episode appears to be over. But a wet March would be welcome for some dry parts of the country.
"In the West, we'd love a 'March Miracle' of rain and snow," Patzert said. "Actually, across the country, a cold snap with snow and rain would be welcome. But the switch out of the negative AO works against it."