With a strong La Nina pattern in place, winter was forecast to be slightly warmer than normal but that hasn't happened. December and January have averaged far below normal temperature wise. December was the 17th coldest on record in Little Rock. So what happened?
The Arctic Oscillation is a measurement of pressure over the north pole. When the pressure is high, cold air plunges into the United States. When low pressure is over the pole, the cold air usually stays bottled up to the north.
As Ed explains in this Weather 101 video, a negative arctic oscillation can overtake even a strong La Nina.