Arctic oscillation

This helps the middle latitude jet stream to blow strongly and consistently from west to east, thus keeping cold Arctic air locked in the polar region.

The oscillation still fluctuates stochastically between negative and positive values on daily, monthly, seasonal and annual time scales, although meteorologists have attained high levels of predictive accuracy for shorter term forecasts.

[6] This zonally symmetric seesaw between sea level pressures in polar and temperate latitudes was first identified by Edward Lorenz[7] and named in 1998 by David W.J.

In the positive phase, higher pressure at midlatitudes drives ocean storms farther north, and changes in the circulation pattern bring wetter weather to Alaska, Scotland and Scandinavia, as well as drier conditions to the western United States and the Mediterranean.

This keeps much of the United States east of the Rocky Mountains warmer than normal, but leaves Greenland and Newfoundland colder than usual.

Another snowstorm swept Catalonia as well as neighbouring French departments (Languedoc-Roussillon, Midi-Pyrenées) on March 8, depositing 60 cm of snow in Girona.

These negative values of the AO during 2010 and following into the next winter allowed colder air to penetrate much further south than usual into sub-tropical South Florida which brought record breaking low temperatures and months registered in many locations [12] and the coolest average monthly minimum temperatures for February, March and December that year in the tropical beach getaway of Cancún, up to over 4C below the climate period averages.