BBC Weather forecasters have explained whether extreme wintry conditions and major snowfall could hit the UK this winter as a result of El Nino. While the climate phenomenon may increase the chance of disruption to the polar vortex, forecasters caution that heavy snow is far from guaranteed.
El Nino and the polar vortex
Experts have suggested this year's El Nino, expected to be the strongest ever, could lead to the polar vortex collapsing. The polar vortex is a ring of strong westerly winds surrounding the North Pole, and when it weakens or collapses it can affect the jet stream.
The Met Office has said El Nino could weaken the polar vortex over the coming months, potentially leading to a process known as sudden stratospheric warming. This causes cool air to rush downwards, changing the position of the jet stream and potentially causing a 'blocking pattern' that keeps cold conditions locked in place.
Sudden stratospheric warming and the Beast from the East
Sudden stratospheric warming is what led to the infamous Beast from the East in 2018, during which 22 inches of snow fell in some parts of the UK. However, BBC Weather forecasters say there are no guarantees of extreme wintry weather this year.
They explain that when the polar vortex wobbles, “it can deliver colder northerly or easterly winds which can bring the UK its coldest winter weather”. However, they add: “It does not always translate into changes in weather patterns at the Earth's surface.”
Mixed evidence on winter impacts
“Equally, periods of a meandering jet stream and cold winter weather often occur without significant changes in the polar vortex,” they note. Moreover, even though El Nino can make it “more likely that the polar vortex becomes disrupted, increasing the chance of ice and snow”, the BBC says “the links are unclear and the evidence is mixed”.
The so-called Big Freeze of 2009/10 was the coldest winter in three decades at the time and coincided with an El Nino, but so did the unseasonably warm winter of 2006/07. The BBC Weather forecasters conclude: “So while El Nino is already having big impacts on global weather, and may influence the polar vortex later in winter, snow and ice in the UK is far from guaranteed.”
