Welcome to my weather forecast for winter 2023/24 for Reading & Berkshire, though it is broad scale enough to easily be applied to much of central/southern England.

Firstly the usual caveat – seasonal forecasting is experimental, and I actually seem to be getting worse at it! Some of this will be wrong – there is nobody who can accurately predict a month of weather repeatedly, certainly nobody can do three months. If this is all right, then it is at least partly down to luck.

But, we can still have a reasonable idea about the more likely outcomes, given background signals, especially in winter where background signals are always much stronger and more effectual on our weather.

That said, events happen that shape the weather outside of the background signals – and this is where long-range forecasts tend to go wrong.

Also thanks to Louise for the photograph. Yes, I am braving a snow photograph – though how could I resist the accomplices?

Background Signals

El Niño tends to mean milder and wetter conditions earlier in the winter, drier and colder later in the winter.

We are in the easterly phase of the Quasi-Biennial Oscillation (QBO), which tends to mean the westerly flow is less strong – so high pressure and even easterly flows can be more likely (ie colder conditions).

The wild card in winter is always the chance of a sudden stratospheric warming (SSW) event – and these seem to be more common in winters that have the combination of El Niño and an easterly QBO. SSW events can lead to events like 2018’s Beast From The East – many significant winter events in years gone by had an SSW 2-4 weeks beforehand – but it never guarantees anything cold, just significantly increases the chances.

The sea surface temperatures in the Atlantic are in what is known as a tripole – warmer than normal to our north-west, cooler than normal to our west, warmer than normal to our south-west. This is thought to increase the chances of the jetstream tracking further south, and hence allowing colder air south – winters of 2009/10 and 2010/11 had such a pattern.

These are all in favour of cold weather during winter, or at least parts of winter.

However, we live in a warming climate – this year is likely the warmest on record so there is that to take into account.

And the Indian Ocean Dipole is in a strong positive phase, which a fair few years back was thought to be the main driver of our mild winter, when it looked like the background signals were pointing towards cold. So there is some conflict in background signals, as there normally is.

In the shorter term, the Madden-Julien Oscillation is pointing towards the chance of colder conditions towards the end of December.

December

After a cold and fairly dry start to the month, the Atlantic will take over and it will become unsettled, with rain and sometimes wind. Generally becoming milder, though the odd colder day possible. Around or just after mid-month, high pressure will likely try to establish itself, at least for a few days.

Before Christmas, more likely we revert back to something changeable, with some milder days with rain, some drier and cooler days, though less confidence on this period. Towards the end of the month (perhaps in time for Christmas but more likely after), increased chances of cold weather spreading down from a more northerly context – snow and ice become possible, though it may well be fairly marginal with the jetstream not likely to especially calm down.

Overall I expect above-average rainfall, slightly above-average temperatures, slightly below-average sunshine amounts.

Confidence level of 75%.

January

January does look like a particularly unsettled month – probably on the cold side to begin, with chances of snow, though again quite possibly marginal with mild weather trying to regain control.

It shouldn’t take too long for this to happen – and become generally mild with rain and wind, perhaps some named storms. It likely wouldn’t always be mild – some colder conditions will be plausible as low pressure systems clear with short spells of north-westerly or northerly winds, perhaps with wintry shower and overnight frosts. But generally the theme for January is unsettled and fairly mild.

Suggestions that towards the end of the month, high pressure over the continent may become more influential – so drier, perhaps cold and frosty – though less sure on this.

Overall I expect above-average rainfall, slightly above-average temperatures, slightly below-average sunshine amounts.

Confidence level of 65%.

February

The signs point towards an SSW being a bit more likely than normal this winter, so I’m tentatively suggesting February as a cold month, but I’m also assuming that both an SSW happens, and it is favourable for cold conditions in the UK.

Cold, with overnight frosts and snow showers at times, especially if we end up with an easterly flow, though often dry.

However, if an SSW does not happen, I still think a fairly dry and fairly cold month is the more likely outcomes, with overnight frosts and fog possible.

Overall I expect below-average rainfall, slightly below-average temperatures and slightly above-average sunshine amounts.

Confidence level of 40%.

In Summary…And Early Spring Thoughts

In summary, I’m expecting an unsettled and often mild December and January, though with some potential for cold and wintry spells. February has higher chances of cold and snow, though nothing is certain in long-range forecasting.

Early suggestions for spring, are of a colder than normal spring, at least to start.

Enjoy! And roll on spring warmth so I can get back into the sunshine.