THERE has been a cold start to the year, with temperatures struggling to get above freezing, but more wintry weather could be on the way.
Scientists at the University of Reading have detected a major sudden stratospheric warming (SSW) event high above the Arctic – and that could bring unusually cold and snowy conditions to the UK.
As with all weather forecasts, this extremely cold front might take a different direction. However, the university says that we could be facing a new Beast From The East that was seen in February and March three years ago.
An SSW is where temperatures in the layer of the atmosphere called the stratosphere, around 10-50km above the Earth’s surface, warms by up to 50°C in a matter of days. This can then affect the lower atmosphere, altering the jet stream and increasing the likelihood of unusually cold weather.
And it could arrive in Europe at any time over the next six weeks.
Simon Lee, an atmospheric science and weather forecasting researcher at the University of Reading, said: “A weakening of the jet stream often occurs after an SSW, meaning the UK is now more prone to outbreaks of colder weather from the north and east than it was before.
“A weakened polar vortex can last for up to two months, so there is an increased likelihood of colder, drier weather occurring in Europe sometime in the next 4-6 weeks due to weaker Atlantic westerly winds.
“This also means we are less likely to see the kind of windstorms and heavy rainfall associated with a strong jet stream that we experienced last winter.”
SSW events generally occur on average slightly more often than once every other winter. When the polar vortex is strong, the jet stream is often strong – bringing a milder winter to the UK and often an increase in Atlantic windstorms.
The university said that that last winter, the polar vortex was unusually strong, leading to wet and mild winter with several major storms – such as Ciara and Dennis.
SSWs are just one factor that influence UK weather. The Met Office says the La Nina conditions seen in the Pacific, which tends to bring milder weather to the UK in the second half of winter, is one factor that could counteract the likelihood of extreme cold weather in Europe this winter.
“Awakening a new Beast this winter is far from a certainty, as this SSW is only one atmospheric factor which can influence the weather in the UK,” Mr Lee said. “For example, the most recent major SSW on January 2, 2019 was not followed by a prolonged spell of cold weather.”
The Met Office currently predicts “there is a greater than average chance of cold spells across the UK with the associated risk of wintry hazards” towards the end of month.
