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.…