The UK could see an “increased chance” of cold temperatures in the coming weeks due to one in a 250-year weather event, which the Met Office has said is the “first in our observational records.”

This extended winter period (November to March) is the first time the forecasters have seen three Sudden Stratospheric Warming (SSW) events take place across the UK “since records began” in the mid-20th century.

Met Office research has suggested the possibility of having three SSW events in one winter period is “a one in 250-year chance, although it is more likely to happen during an El Niño winter, such as this winter”.

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.”

He added: “Although this is very rare, we also found that the chance of multiple SSW events is increased during El Niño and so the chance of multiple events this winter is raised.”

What is a Sudden Stratospheric Warming (SSW)?

The Met Office explained: “A SSW is a disruption of the normal westerly air flow 10 to 50 km above the earth. This often makes the jet stream meander more, which can lead to the development of a large area of high pressure over northern Europe at the Earth’s surface.

“This can ‘block’ the Atlantic low-pressure systems which are responsible for the relatively mild, wet and windy weather that often occurs in UK winters. This blocking pattern increases the chance of cold, dry weather in the UK and mild, wet and windy conditions for southern Europe.

Will the UK get snow this winter? 

 

“However, the impacts of an SSW do not always equate to cold weather, for example, we have only seen intermittent drops in temperature around the two SSW events early this winter and typically around 70% of events are associated with a cold snap.”

Although an SSW is just one of a number of global drivers that can affect weather in the UK, “the current SSW is consistent with the latest long-range outlook for March which suggests a continued increased chance of blocked, high-pressure conditions to the north of the UK and a southward shift in the Atlantic jet stream,” revealed the forecasters.