After several days of snow already this year, could February be getting even colder than January?

The North Pole’s high-altitude air has suddenly warmed up and is set to shunt cold low-level air south towards Britain.

The event, known as a Sudden Stratospheric Warming (SSW), usually chills for two weeks or longer and brings widespread snow.

It has not occurred for four years, official government records show, but there is a risk of a similar occurrence happening later this month.

It could soon be feeling like the North Pole in Cambridge
It could soon be feeling like the North Pole in Cambridge

What is Sudden Stratospheric Warming?

An SSW event occurs when that mass of cold Arctic air, known as a Polar Vortex, expands and gets pushed south, carried along with the jet stream.

It is likely to become rather cold in the East, and from mid-February until the beginning of March, high pressure will gradually build​ over the continent​.

This will lead to another icy snap, with lots of clear, dry weather with night-time frosts.

The warning is contained in the UK government official February to April forecast being briefed to the Cabinet Office, transport bosses, councils and emergency services.

The February to April contingency ​outlook said: “The probability of Sudden Stratospheric Warming is higher-than-normal in February.

“These events disrupt the stratospheric polar vortex and, more often than not, bring cold weather to the UK.”

Some forecasts claim there is a chance of a sudden stratospheric warming event in the coming weeks, leading to colder weather from the east towards the end of the month.

How will Sudden Stratospheric Warming affect the UK?

Forecaster Dr Dave Reynolds, of The Weather Channel , said the mass of Polar air was set to expand and possibly drag bitter air towards the UK.

He explained: “There is a clear indication of an imminent split in the polar vortex, currently located over central-western Greenland.

“The main centre will drift to the Canadian Plains, while a new ​area will form over northern Russia​.

It's going to get chilly...
It's going to get chilly...

“This will drift towards the Caspian Sea, then westwards across the Mediterranean, Iberia and out to the near Atlantic during the next two weeks, weakening as it does so.

“The process of vortex splitting is accompanied by sudden stratospheric warming, whereby temperatures in the stratosphere rise.

“This warming can then extend downwards through the depth of the atmosphere and result in an increased risk of blocking, which in winter-time raises the chance of widespread cold conditions developing.”

This ​prevents milder conditions from the west heading across the Atlantic allowing colder air to dominate. However, there’s no guarantee Europe will see increased cold.

Dr Reynolds added: “To go from vortex splitting and sudden stratospheric warming to a blocked pattern won’t occur overnight, it’s a process that can actually take some 10 days to three weeks.”

The forecaster said computer models indicated a cold, blocked pattern over Scandinavia for the last week of February and first week of March, reinforced by a possible polar vortex split and accompanying stratospheric warming. He said experts were closely monitoring forecasts for more evidence of the imminent phenomenon.

When was last occurrence of Sudden Stratospheric Warming?

The last SSW event occurred four years ago, according to official data, and brought the coldest March for 51 years to Scotland, with snow and -12.5C lows as late as March 31 in Braemar, Aberdeenshire.

SSW events also triggered -16.1C lows in Altnaharra, ​the Scottish ​Highland​s​,​ during November 2010 - starting the month-long Big Freeze in December 2010.

