London Winter Forecast 2021/22

This winter is most likely to be on the colder side of average with near normal rainfall.

While the modelled prognosis for the first half of December looks unsettled with an Atlantic influence evolving from the current chilly NW’ly to a mild SW’ly, local analogues of the climate of London suggest the season could be a bit of a rollercoaster with spells of wet, windy and mild weather alternating with dry, calm and cold.

A large factor to consider this winter is the presence of a slight La Nina that is forecast to evolve cooler.  

Given the uncertainties involved with the influence of ENSO I’ve decided to stick with analogues found in local data that stretches back to 1797.

Overall then the probabilities for the next 90 days are.

MeanProbabilityRainfallProbability
Mild (>5.9C)14%Wet (>178mm)19%
Average (5.1C – 5.9C)38%Average (107-177mm)62%
Cold (<5.1C)48%Dry (>107mm)19%

The above table doesn’t reveal a great deal in that extremes can be hidden in a month or season that finishes broadly average. So I decided to look closer at the winters that were revealed in the analogues.

December

The first month, as already mentioned, looks like it will be on the mild side with possibly a notable storm off the Atlantic before things calm down over Christmas – the period between Boxing Day and New Year’s Eve possibly presenting the best chance of any lying snow in this region.

The below graphs are a smoothed representation of the years revealed in the analogues most similar to this autumn.

What is probably most interesting is that the analogues that shared a similar ENSO / La Nina index to this autumn tended to ‘turbo charge’ any yo-yoing in the weather type, be that super-mild or abnormal cold.

December probabilties for maxima:
Mild: 48%
Average: 19%
Cold: 33%

And precipitation.
Wet: 33%
Average: 29%
Dry: 38%

So, the month overall will be mild and slightly dry

January

The first month of 2022 probably represents this region’s best chance of lying snow this winter. A mild start perhaps with a falling off of temperatures in the final third of the month and a cold spell of a week or so. As with December the influence of La Nina could tend to boost the swings in the pattern.

January probabilties for maxima:
Mild: 33%
Average: 10%
Cold: 57%

And precipitation.
Wet: 19%
Average: 43%
Dry: 38%

Greatest chances for January, then, are cold with average precipitation.

February

The second month may see a slight return of the cold spell in January before temperatures recover for a mild and wet spell in the second half.

February probabilities for maxima.
Mild: 33%
Average: 15%
Cold: 52%

And precipitation.
Wet: 38%
Average: 38%
Dry: 24%

The stats suggest on the cold side overall with average to above average rainfall. Perhaps the depth of the cold skewing any very mild second half of the month?


The extremes that no-one can forecast

As well as the very mild winter of 1989/90 the analogues also revealed the very cold winter of 1978/79. There were others but their occurence makes the probability of a repeat at either extreme at less than 10 per cent.

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