The polar vortex just broke a new record but experts aren't sure what it means for this winter's weather
www.bbc.com
... The spiralling winds of the polar vortex high above the Arctic have reversed direction marking the earliest 'major sudden stratospheric warming' on record.

These polar winds usually blow in a westerly direction keeping cold air locked high above the North Pole.

However in recent weeks the polar vortex has weakened and shifted position. Observations have now shown a switch to easterly winds, which experts say defines a 'major sudden stratospheric warming' or SSW.

Similar disruptions can occur during winter and are often linked with colder weather in the UK. But this event happening so early in autumn is unprecedented in modern observations.

What is sudden stratospheric warming?

The polar vortex is a normal feature of our climate in the months around winter. As the North Pole tilts away from the sun, temperatures above the Arctic drop and strong westerly winds form in the stratosphere.

Sudden stratospheric warming (SSW) is when a rapid and dramatic rise in temperature occurs high in the stratosphere, roughly 10 to 30 miles (15-50km) above Earth's surface.

It can happen due to atmospheric disturbences causing a shift in the position or shape of the polar vortex which can make its winds weaken.

This sudden stratospheric warming (SSW) can eventually lead to the strong westerlies reversing into easterly winds.

In the following days and weeks these changes can slowly filter lower down in the atmosphere altering the position of the jet stream which drives what type of weather we experience on the ground. ...