Polar vortex weakening: Sudden stratospheric warming underway

Warming is underway in the stratosphere, and the stratospheric polar vortex is weakening. What does this mean for 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.

When the polar vortex is strong in winter, it has a strengthening effect on the jet stream. A mild, westerly wind will then prevail in central Europe. When it weakens, as it is currently, pulses of cold air can be sent southwards, as the jet stream meanders.

During a Sudden Stratospheric Warming (SSW) event, temperatures over the Arctic can rise rapidly in a short period of time. As it warms, the vortex weakens, and the polar vortex can either displace, or split.

These events can be classified as "Minor" or "Major"; "the latter requires a temperature jump of at least 50 degrees and the zonal winds reverse, rather than just weaken.

Weather models were indicating just mere days ago that a Major Stratospheric Warming event was on the cards, to next to none, with a rapid vortex recovery. A technical warming does still seem possible.

For us, this means a cool down is still possible towards the end of the month, but at this stage significant cold and wintry weather isn't expected.

However, at the very least as the jet stream weakens and wobbles, a westerly air flow is less likely, resulting in a greater chance of drier weather across the UK and Ireland.

Back in January 2024, we saw another minor SSW event, which had little to no impact on our weather and the same may well happen again.

There is often a lag of a couple of weeks after a stratospheric warming event for the cold air to propagate and affect our weather pattern in the troposphere, but also no guarantee of colder weather.