What Is the Polar Vortex and How Can It Affect Winter Weather?
The polar vortex is a large area of cold air surrounded by strong winds that circles one of Earth’s polar regions. The term usually refers to the stratospheric polar vortex , which forms high above the Arctic during winter when the polar atmosphere becomes extremely cold. A separate, lower atmospheric circulation also influences weather closer to the surface. A strong polar vortex can help keep the coldest Arctic air concentrated near the pole. However, the vortex can become stretched, displaced, or weakened when large atmospheric waves disturb its circulation. One important event is sudden stratospheric warming , in which temperatures high in the stratosphere rise rapidly and the usual west-to-east winds can weaken or reverse. When the polar vortex is disturbed, parts of the cold air may move southward into lower latitudes. This can contribute to outbreaks of very cold weather in parts of North America, Europe, and Asia. It does not mean that every disruption will produce a major snow...