Britain has seen a sharp dip in temperatures this week, with parts of rural Scotland plunging to almost -10C. However, some forecasters believe the cold could get worse in the run-up to Christmas.
The polar vortex is a large circulation of winds up to 30 miles (50km) above the earth, which can have a knock-on effect on the climate we experience on earth.
The spinning, rapid winds above the north pole impact the jet stream, and therefore the weather.
If the polar vortex is strong, it keeps the cold polar air up north, and therefore doesn’t impact the jet stream and push cold air over the continents.
But if the vortex is weak, it allows colder air to push down over the jet stream and leak icy air into our atmosphere.
Meteorologist Andrej Flis told Express.co.uk: “The weakening of the stratospheric polar vortex is well underway.
“In the past days, the polar vortex reached 40-year record strength for this time of year.
“It would likely strengthen even further, but its rise to power was stopped and reversed, due to two pressure/temperature waves that press onto the vortex.
“That reduces the speed of the stratospheric polar jet stream.
“That is a strong sign of a collapsed polar vortex, and high probability of a Sudden Stratospheric Warming event by the end of the year.”
This term - sudden stratospheric warming - might be confusing, but it actually means colder weather on land.
The event is called ‘warming’ as the conditions warm suddenly in the stratosphere, but results in a rapid cooling lower down as a result of the jet stream pushing the cold air down.
Meteorologist Simon Lee tweeted: “Vortex disruption looks nailed-on, but will it turn into our third major warming in three consecutive winters…?”
‘The Beast from the East’ of 2018 was attributed to a Sudden Stratospheric Warming, which saw the UK blanketed in unprecedented icy weather.
BBC Weather presenter Helen Willetts has been forecasting cold conditions already taking their toll on the European continent.
She said: “The central area of the Mediterranean is looking to have some more severe weather.
“Strong winds continue to push that water and those winds and that rain northwards.
“Heavy snowfall once again across the Alpine region.
“To the east of that temperatures are well above average.
“Temperatures will steadily rise this week across Scandinavia but it’s still cold here, we’ve still got some snow to come.”
For more on how the polar vortex works, head HERE.