YORK may be due to get snow next week - but what is sudden stratospheric warming that could to bring the cold weather to the city?

The Met Office is suggesting the possibility of snow next week, despite the meteorological spring officially beginning today.

In recent years some extreme cold, winter snow events have all been connected to the surface effects of sudden stratospheric warmings, such as those in 2009/10, 2013 and ‘the beast from the east’ in 2018. 

The Met Office said the term sudden stratospheric warming refers to what is observed in the stratosphere - a rapid warming, up to about 50°C in just a couple of days, between 10km and 50km above the earth’s surface.

"This is so high up that we don’t feel the warming ourselves. However, usually a few weeks later, we can start to see knock-on effects on the jet stream, which in turn effects our weather lower down," a spokesperson said.

The Met Office said the stratospheric sudden warming can sometimes cause the jet stream to ‘snake’ more - and this tends to create a large area of blocking high pressure. Typically this will form over the North Atlantic and Scandinavia. 

This means that northern Europe, including the UK, is likely to get a long spell of dry, cold weather, whereas southern Europe will tend to be more mild, wet and windy.

On the boundary of these areas, cold easterly winds develop and in some cases the drop in temperatures leads to snow, which is what happened in early 2018.

The Met Office said strong westerly winds circle around the pole high up in the stratosphere in the winter every year. This is called the stratospheric polar vortex and it circulates around cold air high over the Arctic.

In some years, the winds in the polar vortex temporarily weaken, or even reverse to flow from east to west. The cold air then descends very rapidly in the polar vortex and this causes the temperature in the stratosphere to rise very rapidly, as much as 50­°C over only a few days - hence the term sudden stratospheric warming.

To read more about stratospheric sudden warming, visit the Met Office website.