Winter got off to a fast start in the Lower 48 even before it was technically winter. Waves of cold gripped the eastern two-thirds of the United States and several winter storms tracked across the region.
Conditions have since eased some, but the heart of winter lies ahead. Will cold and snowy conditions return and turn more harsh?
The polar vortex, the roaring river of air winding around the North Pole, holds the cards. What they reveal could be very disturbing and a harbinger of extreme winter weather in the Eastern United States.
Judah Cohen, a climate researcher at Atmospheric and Environmental Research, monitors the condition of the vortex, everyday checking the latest prediction models for any sign of disturbance. He is concerned about what some models are projecting at the end of December or early January.
When the vortex, perched some 60,000 feet high in the atmosphere, is stable, winter conditions over the United States and Europe tend to be rather ordinary. Winter is still winter, with the normal mix of storms, cold snaps and thaws.
Visualization of stratospheric polar vortex on Dec. 18. (earth.nullschool.net)
But when the vortex is disrupted, an ordinary winter can suddenly turn severe and memorable for an extended duration. “[It] can affect the entire winter,” Cohen said in an interview.
Rewind to February of last year to understand the implications. Up to that point, the vortex had held in its stable state, and the winter was a mild, unremarkable one. But then, abruptly, the vortex split.
The fracture set off a chain reaction, which first unleashed a punishing blast of cold in Europe and Asia. The media dubbed the cold snap the “beast from the east” as frigid Siberian air flooded the continent.