by Dave Hennen
CNN Senior Meteorologist
and Brandon Miller
CNN International Senior Meteorologist
Much of Europe continues to be in an icy grip that shows little signs of relaxing its hold. Eastern Europe has been particularly hard hit as the death toll climbs to over 250. The cold wave which began in late January shows no signs of letting up.
Heavy snows have accompanied the cold over much of Europe. Rare snows have been seen as far south as the Sahara Desert. On Sunday Tripoli, Libya reported several inches of snow, their heaviest snow since the 1950’s.
Rome even saw a rare snow over the weekend.
Berlin dropped to -4 and Paris to 14 degrees this morning marking the coldest either city has been since the cold snap began.
An unusual dip in the jet stream, the river of air that divides cold air to the north and warm air to the south is to blame for the cold onslaught.
This pattern allows cold polar air right from the North Pole that would normally be kept much farther north spill directly south and cover almost all of Europe. This unusual pattern can be explained by the Arctic Oscillation, a meteorological index used to keep track of pressure patterns.
When the index is positive, as it has been for much of the winter thus far, winds in the jet stream increase in speed, which traps much of the cold air in the Arctic regions. When the index turns negative, as it has over the past two weeks, the winds decrease in speed, making the jet stream more susceptible to major bends. The jet stream over Europe right now is being pushed south around an intense area of high pressure located over western Russia, which allows the frigid temps to travel much farther south than they normally would. This area of high pressure is responsible for not only the severity of the cold outbreak, but also its longevity, which has really made this cold snap historical. The high pressure area formed the last week of January and has remained nearly stationary, all the while bringing Siberian air into the rest of Europe. Kiev, Ukraine has seen temperatures at least 10 degrees F below their average for 13 consecutive days, reaching a minimum of -17 F on February 3rd.
According to computer models, this pattern will continue through this week, but may begin to break down this weekend.