Figure caption, What is the polar vortex?

By Simon King

Lead Weather Presenter

High above the Arctic, powerful winds usually circle the North Pole each winter, helping trap some of the coldest air on Earth.

But this circulation, known as the polar vortex, has weakened and shifted position in recent days.

While such disruptions can occur during winter, scientists say an event this early in November is unprecedented in modern observations.

Similar disruptions in past years have sometimes been followed by colder weather affecting parts of Europe and North America.

However, as this is happening so early in the season, there are few historical examples to compare with and it could throw current winter forecasts into even more uncertainty.

What is the polar vortex?

The polar vortex develops every autumn as temperatures fall in the Arctic.

Strong westerly winds form in the stratosphere, roughly 10 to 30 miles (15-50km) above Earth's surface, locking the coldest air near the pole.

Atmospheric disturbances…