(Bloomberg) -- Europe is forecast to have a cool and windless November as a weak La Niña weather pattern finally arrives, bringing a higher risk of polar vortex events this winter.
Half of the 14 La Niña winters since 1990 brought colder conditions to Europe in November, Matthew Dobson, an energy meteorologist at forecaster MetDesk, said in a presentation in London late Wednesday. More than one in three of those also resulted in lower temperatures for the other winter months.
While there is still a 25% chance that La Niña — a cyclical cooling of the Pacific Ocean — won’t materialize, the base-case scenario is for a weak pattern to take hold, according to MetDesk. The risk of extreme weather events known as “sudden stratospheric warming,” which can lead to cold snaps in the Northern Hemisphere, is higher during La Niña winters, Dobson said.
Just over 70% of La Niña winters since 1980 have seen at least one such event, including the so-called Beast from the East in February 2018. That brought heavy snow and Arctic temperatures to the UK, and rapidly depleted natural gas storage sites across Europe, causing panic among traders and a spike in energy prices.
However, the timing of such events is important. A sudden stratospheric warming in January offers a greater potential to trigger a significant cold snap in the following weeks than a similar event later in the winter.
Cold November
MetDesk expects colder than normal weather from the middle to end of November, according to Ben Davis, another of the company’s energy meteorologists.
“A bit of elevated threat of cool, low-wind conditions into northwest, central Europe is our viewpoint for November,” he said. “Certainly a week or two of cold, relatively low wind conditions” appear “fairly likely.”
The rest of the winter is likely to be milder, but not as exceptionally warm as last year, Davis said. December is forecast to be “relatively mild,” with temperatures about 1C above average in northern Europe.
A strong polar vortex in December can lead to mild and windy conditions into January, but a weaker one could bring a cooler, low-wind forecast, Davis said. For now, January temperatures are expected to be slightly above normal, but the forecast remains uncertain.
There is a high confidence of a mild, wet and windy February, about 1.9C above the norm. A sudden stratospheric warming in January may change that outlook.
For the US, La Niña winters bring the risk of cold snaps in December and January, while November and February are forecast to be mild.
For Asia, La Niña may bring cooler conditions in January and February, with a warm November forecast.
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