Mark Hunt weather corner; 124 - Sudden Stratospheric Warming = a cold winter
At this time of year, I often get asked what the prospects are for a cold winter? Back in the day, I even used to have a once-per-year flutter on the likelihood of a White Christmas, relieving Paddy Power of a significant sum on more than one occasion (coincidentally they stopped taking bets shortly after).
It is a difficult question to answer, not least because of the variability in behaviour of ‘our’ jet stream that dictates the weather patterns and its behaviour across the U.K & Ireland.
That said, one weather event that occurs above the Arctic can dramatically increase the odds of us experiencing a cold and sometimes severe winter. It is called a Sudden Stratospheric Warming (SSW) and it occurs above the North Pole. At first read, it seems a contradiction that a warming event can result in colder weather, but it is the effect on the jet stream that potentially causes the change. You can read about the process in more detail here.
Number of major sudden stratospheric warmings (SSW) observed
Image courtesy of www.climate.gov
SSW events can often cause the jet stream to weaken and in some cases reverse, resulting in cold air from the north and east (the so called ‘Beast from the East’) coming into play as we saw in 2010 and 2013 for example. This weakened/reversed flow can stop the progress of Atlantic westerlies in their tracks.
This year, the meteorologists (and most daily tabloids) are getting excited about one of the earliest SSW events ever recorded and the potential for a knock-on effect across The Northern Hemisphere. Now, if you read The Met Office’s explanation referenced above, you’ll deduce that not every SSW event results in a cold winter for the U.K, but they do normally increase the probability of a cold winter. All eyes therefore will be on the run of weather during December and January to see if it does indeed tip towards a cold, dry winter and away from Atlantic rain-bearing westerlies.
The rub is though that some areas of the U.K still need more rain to catch up after the drought of summer 2025, and a SSW event doesn’t lend itself to this weather pattern. That said, after many areas endured 200mm+ of rainfall in November, a run of cold, dry frosty easterlies would be a blessing.
Now, where is that betting slip?
www.weatherstations.co.uk
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