Seasonal Forecasts

Spring Weather Forecast 2024

Spring has started, but its still pretty cold. Welcome to my weather forecast for Spring 2024.

First off, the usual caveat. Seasonal forecasting is difficult, if not impossible. It is mostly about studying background signals, previous year’s weather patterns, pattern matching and expectations of future background signals.

Events scupper this, as does a lack of understanding as to how conflicting background signals may work against each other. It’s pretty much best guesses.

This February was a great example. My forecast was for a colder and drier month than normal, based on background signals overwhelmingly pointing to this outcome being more likely, and also the chance of a sudden stratospheric warming being high, in my view.

Except we had the wettest and warmest February on record. What happened? Well, I assume events – it is often difficult to correlate what signal/event caused weather conditions, though I suspect the sudden stratospheric warming event counted against this time – whilst many lead to cold weather, some actually lead to milder conditions, and this SSW event was unusual in that it reflected back into the stratosphere and powered the stratospheric vortex, and hence we went into wet and mild overdrive. At least, I think that is the cause.

All of which is to say that some of this will be wrong, perhaps very wrong. But hopefully enough will be reasonably inline to make it valuable.

For December and January, my winter forecast behaved reasonably well – had February gone to expectations then I would have been very happy! Also I think I outlined future conditions in my twice-weekly forecasts with good levels of accuracy, quite often the pattern for 1-2 weeks ahead was clearer than normal. And I did drop the idea for a cold/dry February (or at least it turning so) earlier than the professionals did. So I’m content with my ongoing forecasts, if not the seasonal.

I am considering stopping doing these seasonal outlooks, because I question the value, especially when they go so off-course like February does. Feedback welcome – I’m not just looking for positive platitudes!

Finally thanks to Sarah for the photograph – a small donation has been made to The Brooke, as a thank you.

Background Signals

There’s always less influence from background signals in spring.

However, there is likely to be a third sudden stratospheric warming event in early March, or strong and early final warming of the stratospheric vortex – whatever it is classed as, this will increase the chance of easterly and/or northerly winds later in March, and into April – and also push the jetstream south.

It’s slightly annoying that I’m doing the forecast now, as in another week or so, after this stratospheric warming event, things will be clearer. So there’s more uncertainty in this forecast than normal.

El Niño should also increase the chance of cold and dry conditions, at least in March, though that was the case for February too and look what happened.

Easterly phase of the quasi-biennial oscillation should reduce the strength of westerly winds, and increase the chances of easterly flows.

Sea surface temperatures are likely to remain at record highs in the Atlantic, and my reading of this is that there will be more moisture in south-westerly flows, but also much more warmth potential to tap into – depending on if/when high pressure builds over Spain.

March

The sudden stratospheric warming event probably puts hopes for an early spring to bed, but not necessarily.

Most likely, March starts on the cold side, veers mildish then colder, showery days tending to drier days. Through the mid-month period easterly (ish) winds seem likely at times, which should make it colder at times, but also rain and milder weather will be pushing up from the south-west too. Where they meet, snow is possible – but chances do reduce of battleground snow in March, especially down here. A small chance of snow – nothing more.

Later in March, easterly or northerly winds are more likely, so conditions generally on the chilly side with overnight frost probable at times. Otherwise some sunshine, some light/moderate showers, perhaps wintry and some outright cloudy/chilly days. Occasionally, milder and wetter conditions will push up from the south-west.

Quite a mix really – and it will depend on where exactly high pressure sets up to our north (assuming it does) – so an outright wet month is plausible instead, but also a dry and cold month is too. My forecast is for a mixture of the two, with quite a bit of fluctuation.

Overall I expect temperatures to be slightly below-average, rainfall around average and sunshine slightly below-average.

Confidence level around 40% – lower than normal, due to the expected sudden stratospheric warming event in early March.

April

Assuming the stratospheric warming event happens, and the outcome is blocking highs to our north, then I expect April to start fairly chilly with showers or rain at times, with northerly or north-easterly winds being more likely than normal. Overnight frosts still very possible.

There is a weak signal for high pressure to build over Spain in the second half of April, perhaps slightly earlier, so I’m going with that, and suggesting that will increase the chance of warmth (finally!) in the second half of April. Unlikely to be an extended warm spell – likely mixed with some weather fronts bringing rain on a few days, some heavy showers on other days – but some warmer, sunny-ish days too.

Overall I expect temperatures to be around average – though a contrast between below-average to start the month, above-average to end, rainfall slightly above-average and sunshine around average.

Confidence level around 40% again.

May

Background signals really drop off here, and long-range models are conflicting with each other, so in a forecast with lower confidence than normal, I’m even lower on confidence for May.

My best suggestion is for the warmer than normal end of April to continue into the beginning of May, with some very pleasant days – though also a few interruptions – some showers, some occasional weak weather fronts bringing more cloud and rain, with fresher air following.

The latter part of May perhaps looks more unsettled for a time (possibly warm/humid still), though with a trend to much warmer and drier conditions by the end of the month.

Confidence level of 20% – unusually low.

Early summer thoughts and summary

So a mixed spring looks more likely, and not an especially joy-filled spring – with some colder and wetter conditions early. Though with the proviso that uncertainty is much higher than normal.

Early signals for summer do point to a drier and hotter summer being more likely than normal, particularly June.

Winter Weather Forecast 2023/24

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.

Autumn Weather Forecast 2023

Welcome to my autumn weather forecast for 2023.

First thing to note, as always, is that seasonal forecasting remains experimental. Whilst my forecast for June was good, and for August was respectable – for July I predicted a hot month. Aha. Though at least I thought there would be some rain, albeit of a thundery variety rather than Atlantic systems.

So, some of this forecast will be wrong – due to events, it is impossible to give accurate long-range forecasts, but you can give a general guide based on current weather patterns, background signals, etc.

I’m not sure what went wrong in July – did I misread the models? Perhaps but so did every other forecaster who I take notice of, in that case. I know there were unusual plunges of cold air into North America late June, which fired up the jetstream – and then there was some really anomalously warm waters off the coast of North America, which likely gave low pressure systems their oomph this summer.

That’s my working theory on what went wrong anyway.

So whatever I say here, take with a huge pinch of salt.

Thanks to Sarah for the superb photograph, and to all those that sent in – there were a few particularly excellent ones to choose from.

Background Signals

El Niño is still developing and is probably going to be a strong event. I’m not sure that it has too much effect on the UK weather patterns in autumn, perhaps a slightly increased chance of westerly flows later on.

Sea surface temperatures are still warmer than normal around the UK, which increase the chance of warmer than normal temperatures over the UK.

The Quasi-Biennial Oscillation is now in easterly mode – I’ve seen some people on weather forums blame that for our summer weather, but I’m not buying it. Though perhaps it can increase the chance of blocking highs or easterly flows during autumn.

As always, hurricanes/tropical storms and their remnants can affect our weather and add extra uncertainty, especially in September.

September

Speaking of hurricanes, Franklin is the major cause of our hot start to September, pushing high pressure east and allowing us to tap into continental warmth/heat.

So an increasingly hot and sunny start to September, very possible that the highest temperature of the year is recording during September, though I think we’ll stay short of the UK all-time September maximum – which is 35.6’C. Some warm nights too, though some early morning mist/fog/low cloud in places.

Towards the middle third, there will be (small) chances of thundery showers before the heat gradually faces, and by around mid-month or just after, we should be in something more changeable – perhaps briefly unsettled.

In the latter part of the month, probably some variation with some showers, but a return to warm and dry looks more likely overall. Bear in mind that hurricanes/tropical storms far to our west add uncertainty to this.

Overall I expect well above-average temperatures, above-average sunshine, and below-average rainfall – unless you catch a particularly heavy downpour during mid-month.

Confidence level of 85%.

October

Signals are weaker for October though there is a fairly notable signal for high pressure close to the east of the UK.

A dry start may give way to a spell of more unsettled weather into the first half of October, perhaps some very heavy, showery rain at times, and quite windy. Likely mild and occasionally warm.

In the latter half of October, it seems more likely that the high to our east will push west somewhat, meaning rain stays to our west most of the time, and it should generally be dry, mild with some overnight mist/fog.

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

Confidence level of 60%. The main risk is that the high pressure block is further east and low pressure systems get stuck over the UK – bringing a wetter month than I expect.

November

November I think will more likely start dry with high pressure close by. Overnight frosts with some morning mist/fog patches possible. Some sunny days, some cloudy days, temperatures around normal for the time of year.

During the latter part of November, the jetstream should pick up and we’ll have a more westerly flow – some rain at times from weather fronts though I suspect the bulk of the heavy rain and strong winds will be towards Scotland. Generally mild/very mild under such a set-up. Uncertain on cloud/sunshine amounts.

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

Confidence level of 50%.

Overall and Early Winter Thoughts:

So drier and warmer than normal for autumn, is what I expect. We shall see!

Early thoughts for winter are mostly for a mild and dry winter with a strong signal for higher than normal pressure over Europe.

I wouldn’t preclude a cold spell, and there will be some rain at some point, but overall drier and milder than normal seems the most likely outcome – albeit it’s 3 months away!

Summer Weather Forecast 2023

Welcome to my Summer Weather Forecast 2023. I think you’ll like it.

Some of this forecast will be wrong. That is the case for all seasonal forecasts (unless a forecaster gets lucky). We can have some confidence on general trends, but picking out short-term features or getting the timing right of changes, becomes impossible after a couple of weeks. And then the general trends can change – what you think was likely, then gets disturbed by a major event somewhere in the world, which then adjusts the jetstream, etc, etc.

But hopefully I can give a reasonable guide.

I’m fairly happy with my spring forecast. It was cold to start March, and wet to end as I thought – though wetter than I expected. April I predicted average temperatures, slightly above average rainfall and slightly below average sunshine – which was broadly the case. May I thought we’d be in an easterly flow, which did dominate and still does into June, but low pressure was further south than I expected – I had expected it to be a bit closer and hence warmer with showers for the latter half.

Thanks to everyone that sent a photograph in – my choice is Dave’s with a gloriously sunny sky, though with hints of showers to come.

Background Signals

There isn’t really a lot to talk about, though the key factor is extreme temperatures don’t have the same base as they did last year, as the soil moisture profile is higher over Europe, which should just temper the possibility of extreme temperatures.

However, on the flip side, sea surface temperatures are higher, if not much higher, across much of the eastern Atlantic, from Spain/Portugal, all the way through to Ireland, which I’d suggest makes hot weather a little more likely.

It is contested, but personally I believe that winter sudden stratospheric warming events have an imprint into summer months, especially late season SSWs, like we had, and increase the propensity of blocking highs to our north (exactly as has happened in recent weeks). This doesn’t always lead to glorious summer weather for us (2021 for example) but can lead to drier, summer and warmer/hotter weather, depending on exactly where high pressure situates.

I struggle a bit to understand the atmospheric angular momentum theory, but if I understand correctly, the current positive and predicted strongly positive phase, should lead to high pressure to our east, low to our west – a hot but sometimes thundery set-up, down the line in future weeks. I stress that I don’t really understand this that well though.

The other factor is the developing El Niño, which hasn’t occurred yet, but is likely to be confirmed during the summer. It doesn’t have as much impact here as elsewhere in the world (at least as far as we know), but maybe we can infer a slightly greater chance of showers later in the season, at a push. But even that, depends on how strong El Niño becomes, and we don’t know.

All in all, background signals seem to point more to a hotter summer than normal. Though I think long-term models and predicted pressure patterns are more important for this season…and they also point to hotter than normal weather.

An attempt at some details:

June

High pressure dominates the start of June, some cooler and cloudy mornings, but generally sunny and warm afternoons. This changes around 10th June to a more south-easterly flow, with temperatures on the up, very warm or quite hot, but also some thundery downpours in the mix – potentially quite severe in places, but also the potential to miss everything and just enjoy varying amounts of quite hot sunshine.

After mid-month, temperatures generally staying very warm – a few less warm days possible, some quite days also possible, but broadly very warm, sunny spells – a few days likely featuring some heavy, thundery showers, perhaps even a day or two of heavy, thundery rain spreading up from the south, but overall plenty of very pleasant weather is the more likely general outcome.

Overall I expect a warmer than average month and sunnier than normal average. Low confidence on rainfall totals, as it will depend on if you catch any particularly torrential downpours, so perhaps best to suggest more dry days than average.

Confidence levels around 80% – main uncertainty is over whether the mid-month thundery showers turn into a more widespread low pressure system.

July

July looks to see high pressure close to our east or north as the dominant pressure pattern, which means plenty of hot, sunny weather is likely.

Perhaps during the first part of the month, we see high pressure more centred to the north/north-east, which will lead to it generally being very warm/quite hot, though with occasional thundery downpours for us in the south – there is a signal for a wetter than normal summer over Spain/France, so I’d expect we’ll import thunderstorms or at least some instability on occasion from continent.

During the middle and second half of the month is when the hottest part of the summer is more likely, with high pressure more likely to be to our east – low to our west, and depending on where the low is, those Iberian heat-pump scenarios similar to last year (and most summers but last year was notably so) will be more likely – so short very hot spells followed by short unsettled, possibly thundery spells, followed by fine weather – is the more likely general pattern.

Generally the signal for rainfall is higher in the south of the UK than the north, so those who like their holidays in Scotland may approve this year.

Overall for July, I expect above-average temperatures, slightly above-average sunshine and around the average amount of days with rain falling – with rainfall totals dependent on how intense any downpours in your local area are.

Confidence level 75%. I wouldn’t rule out it being the hottest July ever overall – but without the hottest day being recorded. 37’C or so with the “perfect” set-up seems plausible, but 40’C like last year seems too much of a stretch…as it stands.

August

Weaker signals for August, but overall I think the balance for the first half of the month sees more very warm/hot sunny days, though likely some days in the warm with showers kind of theme – the hotter days may also have some thundery downpours too.

Low pressure may be a bit closer to our south-west for the latter month, this bringing more southerly flows – so some hot and humid days, but also some wet days, or at least some thundery downpours. Pretty low confidence though.

Overall for August, I expect above-average temperatures, around average or slightly-below average sunshine, and slightly above-average rainfall.

Confidence level 40%.

Summary And Autumn Thoughts

So, a hot summer but with an increased chance of thunderstorms, I think would be the headline.

Of course, I could be totally wrong. And things change unexpectedly. We shall see.

An early look at autumn currently suggests a warmer but wetter than normal September, and a warmer and drier than normal October/November.

No point in thinking about winter until we know how strong El Niño will be, as that can have an effect on our winter.

Enjoy your summer!

Spring Weather Forecast 2023

Welcome to my Spring weather forecast 2023, for Reading and the surrounding areas.

Firstly a reminder that seasonal weather forecasting remains experimental and probably always will be – however there are normally general trends that look more likely on a seasonal basis, especially in the 1-2 month timeframe.

Some of this forecast will be wrong. My winter forecast wasn’t bad – December was pretty accurate, as was the first half of January and latter half of February – though there was a good 3-4 weeks that I expected to be wet, that were actually dry. I don’t think I saw any seasonal forecast suggesting February would be dry – and I think I read that it was the driest for 30 years.

Also thank you to everyone that sent photographs in, even if half of them didn’t have any weather in them! Thanks to Isabel for the photograph – do drop me a message so I know which charity to donate to.

Background Signals

The main background signal is the sudden stratospheric warming event that started in the middle of February, and we have just had another bout of warming up in the stratosphere. This greatly increases the chance of colder flows from northerly and/or easterly directions, and could impact on and off for around 8 weeks.

We still have La Niña, which I think can increase the chance of westerly flows in March – though this goes against the SSW, so, hmmm, not sure on this. There are hints of El Niño developing towards summer, but this shouldn’t impact spring.

The MJO currently is going into phase 7/8 at a high amplitude, which from my understanding increases the chance of colder flows from northerly and/or easterly directions – but maybe the SSW has impacted the MJO anyway?

March

March is very much expected to start on the cold side, snow falling is very possible, overnight frosts likely at times – though sunny spells during the days also, which with the strengthening sunshine at this time of year means any settling snow shouldn’t last too long.

Towards mid-month, milder and wetter weather will try to push up from the south-west, and where this hits the cold air, there could be heavy, disruptive snow – exactly where the battleground will be is uncertain – it is always more likely to be further north than us, but we are certainly in the game. But likewise, maybe low pressure systems don’t quite get this far north, the cold weather stays and the heavy snow ends up in northern France.

If the snowy battleground is much further north, say Scotland (not especially likely), then we may sneak a very mild day or two.

For the latter part of the month, I expect the colder air to move back south at times, perhaps easterly winds setting in – at this point rain will be more likely than sleet/snow, but wintry showers could still be mixed in, overnight frosts still possible. Temperatures sometimes around average, sometimes below average.

Overall I expect below average temperatures, around average rainfall and around average sunshine.

80% confidence.

April

For the first half of April, I still think we’ll be seeing the hangover of the SSW event, with high pressure to our north, and low pressure either to our south or over the south of the UK.

This means generally fairly cool conditions, with rain or showers at times – an outside chance of some wintry showers, and frost still possible on any clear nights.

The second half of the month has much weaker signals, but I’d favour something a bit drier with some warmish sunshine at times, but still some heavy showers on some days.

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

70% confidence.

May

May I still think will have high pressure to our north and low pressure to our south – though by this time of year an easterly flow tends to be warm rather than cold, as the continent will be warming up.

So a warmer than normal month overall but also a showery month – low pressure probably close enough at times for spells of general rain, but more likely the month will be predominantly warm/very warm, sunny spells but with heavy/thundery showers quite often.

Overall I expect above average temperatures, above average rainfall (though this assumes some of the showers being very heavy) and around average sunshine.

60% confidence.

Early Signs For Summer

At this stage I’d suggest that a repeat of last year’s 40’C is unlikely, due to there being more rain over Spain this spring, and hence soil and sea surface temperatures probably lower than last year.

However, I still think hot and therefore heatwave conditions more likely than normal, just not quite to that extreme – particularly June and July.

August maybe more showery, especially if El Niño becomes a force.