A Sudden Stratospheric Warming is coming. But what does it mean and how will it affect our weather?

In winter, the polar vortex forms at high altitudes over the North Pole. This is a high-altitude low-pressure area that plays an important role in the circulation of the atmosphere. As a result, it also has a direct influence on our weather.

A distinction can be made between two polar vortices in different layers of the atmosphere:

When the polar vortex is strong in winter, it has a strengthening effect on the jet stream. A westerly wind will then prevail in central Europe.

When the polar vortex is weak, the jet stream swings and hot or cold outbreaks may occur earlier. In January, the polar vortex weakened.

During a Sudden Stratospheric Warming (SSW) event, temperatures over the Arctic can rise rapidly in a short period of time. A Major Warming requires a temperature jump of at least 50 degrees.

Statistically, once every 2-3 years, the polar vortex is noticeably weakened. The polar vortex may break or move, resulting in a change from a westerly to an easterly wind.

This is about to take place in mid-February. The European weather model for next week shows above-average temperatures in the region of the stratospheric polar vortex over the North Pole, which will likely lead to a collapse of the polar vortex.

There is a lag on the effect from a SSW on the underlying troposphere however, where our weather takes place. Probably not until late February or in March. Even so, it does not guarantee winter weather at our latitude.

In February 2018, a powerful SSW took place. The consequence of this SSW was eventually felt, with the infamously known 'Beast from the East'.

However the SSW about to occur does not guarantee cold spells; warm spells are also possible. But it certainly makes our weather maps interesting in the coming weeks!