The Met Office has warned that this year's El Niño could be the "largest in living memory" and an "unprecedented event", raising the chances of a cold snap, heavy snow, and stormy weather for the UK.
The phenomenon is likely to increase the likelihood of wetter, stormier conditions across northwest Europe, including the UK, during the coming autumn and early winter, the forecaster said. Atmospheric waves triggered by El Niño destabilise the polar vortex, further increasing the probability of heavy snowfall, experts have said.
Forecasters describe 'unprecedented' signal
Professor Adam Scaife, head of long-range forecasting at the Met Office, said: "I have never seen an El Niño signal this intense in our forecasts. A typical El Niño leads to an equatorial Pacific sea-surface temperature rise of between 1 and 2 degrees, with 2°C being a really big event."
He added: "This implies that if the forecast is accurate - and other forecast systems show similar extreme values - then 2026 will far exceed our recent experience of El Niño and its worldwide climate influences. We should be clear that this is an unprecedented event."
Heightened potential for wet and stormy weather
Scientists say there is twice the normal chance of the October to December period being wet overall, while windy and mild weather is also more probable than usual. Furthermore, the atmospheric waves triggered by El Niño destabilise the polar vortex, also heightening the risk of significant snowfall.
El Niño is a naturally occurring climate phenomenon that develops in the Pacific Ocean when sea surface temperatures across the central and eastern equatorial Pacific become significantly warmer than average, altering atmospheric circulation patterns and impacting weather conditions across the globe.
Risk of sudden stratospheric warming
Dr Will Lang, chief forecaster at the Met Office, described it as a "subtle shift in the odds" rather than a definitive prediction of wetter, milder and windier conditions. He warned that "we are going in with a heightened potential for wet weather, heightened potential for potentially stormy conditions, and that leads through to a heightened potential for flooding".
A Met Office spokesperson added: "Through the latter part of the winter, following a peak in El Niño, the stratospheric Polar Vortex can become weaker, leading to an increased chance of Sudden Stratospheric Warming (SSW) events unfurling, increasing the potential for cold weather."
SSW relates to warming occurring between 10km and 50km above the Earth's surface. This meteorological event can trigger cold air to plunge downwards, disrupting the jet stream and potentially generating a "blocking pattern". As a result, freezing conditions could persist well into the latter months of the year.
