Will El Niño and the polar vortex bring snow to the UK this winter?
BBC Weather | Ben Rich, Lead Weather Presenter
Widespread snow driven by a polar vortex is rumoured to be heading for the UK this autumn and winter. But is that really the case? Headlines have been suggesting it is down to the effects of El Niño but the truth is much more complicated.
El Niño's Impact on UK Weather
For the rest of the autumn, El Niño actually increases the chance of wet, mild, and potentially stormy weather for the UK. Later in winter, it could shift the odds towards cold and snow, but none of this is certain.
Understanding the Polar Vortex
The polar vortex is a ring of strong westerly winds encircling the North Pole every winter, around 10-30 miles (16-48km) above Earth's surface. It forms due to the extreme cold and density of air high above the Pole, which creates strong stratospheric winds.
This phenomenon occurs high up in the stratosphere, far above the troposphere where our weather actually happens. A strong polar vortex tends to encourage a strong polar jet stream in the troposphere, driving areas of low pressure from west to east and bringing mild air from the Atlantic across the UK.
Wobbling Vortex: Potential for Cold Weather
Sometimes, however, the polar vortex can wobble, weaken, or even reverse direction. Over time, this can influence our jet stream, causing it to weaken, become more bendy, or reverse, bringing colder northerly or easterly winds and potentially the UK's coldest winter weather.
El Niño's Connection to Winter Weather
El Niño—a naturally-occurring climate phenomenon in the Pacific Ocean—is continuing to grow and is already the strongest on record. The heat released from the warm Pacific Ocean into the atmosphere impacts global weather patterns. In autumn, it increases the chance of wet and stormy weather in the UK.
In late winter, El Niño's waves of energy can move upwards through the atmosphere, making it more likely that the polar vortex becomes disrupted and increases the chance of ice and snow. However, the links are unclear and evidence is mixed.
The Big Freeze of 2009/2010 vs. El Niño 2006/2007
The so-called Big Freeze of 2009/2010 was the coldest winter in three decades, coinciding with an El Niño year. However, 2006/2007, also an El Niño winter, was unseasonably warm. The Beast from the East in 2018 occurred during a La Niña year, the opposite of El Niño.
So while El Niño has significant global impacts on weather, snow and ice in the UK is not guaranteed. Current forecasts suggest no significant cold or snow is likely in the near future.