Sudden Stratospheric Warming

Polar Vortex and Sudden Stratospheric Warmings

The Polar Vortex is a phenomenon seen in the stratosphere, in the winter hemisphere only. It occurs at a height of around five to thirty miles and forms because air above the winter pole cools markedly in response to the lack of solar radiation experienced there at that time of year. This cooling makes the air more dense, leading to a high pressure area near the surface but a low pressure area aloft, as illustrated by Image 1.

The 'Beast from the East' bites the UK

During the last week of February and into the last week of March 2018, the ‘Beast from the East’ reared its ugly head and brought severe winter weather to much of the UK, in what was the coldest period for a number of years. The bitter winds drawn down from Siberia were caused by the Sudden Stratospheric Warming event that occurred several days previously.

Sudden Stratospheric Warming event

In February 2018, a Sudden Stratospheric Warming (SSW) will take place, resulting in the split of polar vortex in two vortices which may impact our weather later this month (there is a lag time between an SSW and the impact it has on UK weather).

A SSW of the atmosphere refers to a rapid rise in temperatures in the stratosphere (which is found at an altitude of 10 km to 50 km) when the temperature can rise by up to 50°C over a couple of days – and this often leads to cold conditions across the UK.