Welcome to my winter weather forecast for 2022/23 for Reading and the surrounding areas.
Firstly the usual checks and balances.
Seasonal weather forecasting remains experimental and is prone to unexpected events in the atmosphere taking forecasts well off-course. A successful forecast would see more right than wrong, but parts of this forecast will certainly be wrong. Events happen and scupper what look like reasonable forecasts.
My autumn 2022 forecast was alright I guess, I got the signal for cooler and wetter weather for the end of the November for example, but I thought November would see high pressure to the west of the UK (so did the Met Office even during November) – but actually it was to our east.
Further examples, I predicted slightly above-average rainfall for November but it was significantly above, I predicted above-average rainfall for September – it was, I predicted below-average rainfall for October, it was marginally below average.
I’ve definitely had more successful forecasts but it wasn’t a disaster. I don’t keep statistics on accuracy, but I do feel that it is reduced in the last couple of years. Oh well, I’m a software engineer with half a grasp of weather models – meteorology isn’t my job.
As always, take my forecasts with a pinch of salt. It’s just a hobby.
Thanks to Clare for the excellent photograph – a charity donation will be made also. And thanks to everyone that sent one in – and those that send them in on a weekly basis. The forecasts would be more boring without your photographs.
Plenty of background signals at play at the moment, both in the short-term and more long-term. And as usual, they are conflicting.
This is the 3rd winter in a row with a La Niña, which is unusual. It is a more east-based La Niña and not especially strong – both of which are factors that favour blocking to our north/north-west in late autumn and early winter (cold patterns), and favour milder westerly flows later in winter.
However, the atmosphere has been behaving more like El Niño in the last month or so – hence my autumn prediction for a cooler November with high pressure to the west of the UK, was wrong.
The Madden-Julian Oscillation is the pattern of tropical rainfall over the Indian and Pacific Oceans, and can affect our weather, depending on what phase. The MJO tends to be suppressed during La Niña – but has just gone through phases which encourage cold weather in north-west Europe in the following weeks, and there are suggestions that it may be about to repeat this pattern. This is not useful as a forecasting tool after a month or so…and even then can easily be over-ridden.
The Quasi-biennial Oscillation (I’m not making these things up…Google is your friend) is in westerly phase and likely stays that way all winter, which encourages milder, westerly flows.
Sea surface temperatures near the UK are much warmer than normal, which may inhibit easterly flows from being as cold as they could be – but could also, if the air comes from the east and is cold enough, cause heavier showers.
Also there is some suggestion that the North Atlantic sea surface temperatures are conducive to blocking highs to our north. I don’t really know enough about this, but it sounds feasible.
Finally, the polar vortex is currently under pressure in the troposphere, and is being attacked – an attacked polar vortex does lead to flows from the north or east being more likely than normal.
Often, the stratospheric polar vortex being under pressure is the holy grail of winter synoptics through sudden stratospheric warming events, and one led to the Beast From The East in February 2018.
The stratospheric polar vortex currently, I think, is very strong – unlike the tropospheric vortex (we live in the troposphere) – there are suggestions of a possible stratospheric warming event in a couple of weeks, but no signs yet of anything game changing – ie a sudden stratospheric warming event. The chance of one happening seems reasonable given current pressure patterns, which makes late winter more uncertain than normal.
But in the meantime, the attacked tropospheric polar vortex, gives us greater chances of cold and snow than normal.
Phew. Ready for some weather?
So the background signals have been strongly in favour of high pressure close to the UK in December for some time now, and more likely to do so in a cold manner. This is happening.
December starts on the cold side and becomes properly cold as Arctic air spreads down. Overnight frosts expected on some nights, fog possible, and wintry showers also possible – which could easily fall as snow after the first week. Some notably cold daytime maximums also, especially if there is snow on the ground.
Some complications for mid-month as low pressure systems may try to extend north-east towards the UK, which if they arrive would likely bring some heavy snow – though if they go further north than the south of the UK, any snow would turn to rain and it would become milder – though likely only briefly. They may instead not reach the UK (so France would get the heavy snow), and we’d stay cold with sharp overnight frosts, and still some snow showers possible.
For the latter third of December, the more likely outcome is a return to cold conditions, with easterly flows, for at least some of the time, thought this is highly uncertain. Low pressure systems will probably try to push up from the south-west at times, which could bring snow or rain – depending on how they behave. Some short mild spells within a generally cold theme is the more likely outcome for this final third.
Chance of a white Christmas, ie snow falling over those 24 hours? 10% maybe. But normally I’d say 3% – 5%. Chance of snow on the ground on Christmas Day…30% maybe?
Although I can promise that it will be cold enough to snow at times in December, I cannot promise any white stuff will actually fall, but probabilistically, it will not only fall, but at some point there will be settled snow. There’s even a small chance of a lot of snow.
Overall I expect a colder month than normal, slightly below average precipitation and slightly below average sunshine.
70% confidence. The main question is what happens mid-month – if that low pressure (probably originating as a tropical storm in The Azores) does push north, it could change the pattern completely and make it impossible to return to cold.
For January I expect the high pressure to our north/north-east to retreat towards Russia, and high pressure to build to our south – with a re-invigorated Atlantic bringing wet and windy weather at times.
So for the beginning of the month (perhaps by end of December), I’m expecting low pressure to push in from the south-west – at first probably struggling to get much further east than the UK so we’ll end up with southerly winds at times – and prolonged rain if low pressure systems get stuck over the UK. But often mild, perhaps very mild at times.
Generally this picture continuing through much of January – some short colder and drier spells at times, but the emphasis on mild, wet and windy.
Overall I expect above average rainfall, above average temperatures and slightly below average sunshine.
February more likely starts similar to January, with further rain and wind at times, though some drier interludes too. Most likely on the mild side.
Suggestions that the second half of February sees a longer dry and settled spell, though no suggestions yet as to whether it would be more mild/cloudy or cold but sunny.
Overall I expect around average rainfall, around average temperatures and around average sunshine. How ordinary.
60% confidence – the main issue is that if a sudden stratospheric warming event happens before February, then a cold and wintry month would be more likely. However, it is not possible to forecast an SSW this far in advance, so this is a huge unknown, as it is most winters.
Summary and early spring thoughts
So December should be the coldest month (assuming no SSW event), and by far the best chance of snow – it should snow at some point, but this can rarely be 100% promised in our area of the country.
January the wettest month but probably the mildest month. February, more uncertainty (it is two months away so this is normal) but a fairly average month more likely on current signals.
Early suggestions for spring are for a drier, sunnier and warmer than spring overall, with some variation. But this is 3 months away!…