A once-in-a-250-year weather event is about to reach the UK bringing bitter winter conditions, the Met Office has warned.
A Sudden Stratospheric Warming (SSW) event usually strikes every two extended winters, however sometimes there are runs of years without one, said meteorologists.
But this year three SSW events could occur in one year leading to an extremely rare occurrence.
Professor Adam Scaife, head of long-range forecasting at the Met Office, said: “Although we have not seen it before, we recently documented the chances of an unprecedented three SSW events happening in one winter.
“Our research work, using multiple computer simulations, showed that this could occur about once in every 250 winters.”
A Met Office forecast shows snow developing on Friday in parts of Scotland, as the rest of the country enjoys pleasant weather
(Met Office)
The SSW process typically takes place “between 10km and 50km above the Earth’s surface”, meaning we do not notice the warming effect on the ground.
When SSW arises, the normal westerly airflow above the atmosphere makes the jet stream meander more, which can lead to a large area of high pressure over the northern Atlantic, the Met Office explained.
The formation of this high-pressure area can create an obstacle to the Atlantic low-pressure systems responsible for mild, wet and windy weather.
The block then increases the chance of cold, dry weather in the UK and increases the chance of mild, wet and windy conditions in southern Europe.
Although the event does not always lead temperatures to plummet, 70 per cent of SSW occurrences are linked to a cold snap.
Professor Scaife added: “Although this is very rare, we also found that the chance of multiple SSW events is increased… and so the chance of multiple events this winter is raised.”
The chaos-inducing ‘Beast From the East’ snowstorm was caused by this process, which led to 17 deaths and nationwide havoc.
The Met Office weather forecast predicts a chilly weekend with cold winds and some outbreaks of rain.
