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.
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:
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 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.
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!