Seasonal Forecast – Summer 2020

Right. Welcome to my Summer 2020 Weather Forecast.

Let’s start with the caveat. I am not a professional meteorologist and at least some of this forecast will be wrong.

The aim is for more to be right than wrong – and my Spring 2020 forecast went pretty well. Not perfect – that is impossible. But I’m certainly happy with it, I think it was the most successful seasonal forecast for a year or so.

Also this is where I ask you to do some work. I do these forecasts for free and the only thing I ask in return is an occasional share. Share on Facebook, Twitter, Reddit, Mumsnet, Lycos Chat Rooms, whatever your internet poison of choice is. There are links to donate on my website, but I seriously don’t want or expect anything – if you feel thankful then maybe give to charity instead…there are people going hungry and I eat too much…but if you insist on doing so the option is there.

And thanks to Louise for the photograph. I had 150+ photographs, I could easily have used 130+ of them…and some really astounding ones. Out of my very favourites, this was the one that told the story most closely.

A £20 donation to the charity of her choice will be upcoming…please get in touch if you are reading!

It does look like a good summer ahead (unless you want cold and wet), but there will be a fair mix of conditions along the way.

Background Signals

Lets start by looking at some background signals.

The main one that I have my eye on is the sea surface temperatures. Anomalously warmer than normal near us – and colder over the west Atlantic. I feel that this will be the main background signal for our summer, and this should help with high pressure building either over the UK or to our east.

It looks like La Niña might develop later in the summer or early autumn, which a month or so ago I thought would develop around July and bring a cooler and wetter end to summer – now it looks more likely to develop during August/September and even then there is uncertainty. So I’m mostly discounting any effect – but this explains my original thinking of an unsettled August which I am now thinking unlikely.

The Quasi-Biennial Oscillation (look it up if you want to be scared by maths) is heading into easterly phase which can help promote high pressure to our north – but this transition is wobbling and perhaps showing signs of going back westerly which it absolutely should not do for a couple of years. Odd and concerning, but as far as the summer goes, this again helps my confidence that summer may end warm and sunny. I was originally expecting that this could increase the chance of unsettled and cooler conditions towards the end of summer, but the wobble makes me think not.

We are at a solar minimum which I feel favours weather patterns to get stuck in situ more easily – so things take longer to change…hence the long sunny spring. The science on the effect of solar minimum is debatable – it should in theory have favoured a cold winter in 2019/20 and look what happened! Though the record (?) strong Indian Ocean Dipole just overrode all other signals it seems.

The lack of heat over the continent so far this year and relatively wet conditions to our south suggest to me a lower chance of extreme heat – so a lower chance of record temperatures being broken, but it certainly can still be hot or very hot at times.

I also expect a busy Atlantic hurricane season. Whilst I have no idea how this might play out and affect our weather this far in advance – think of it as a greater curveball to my forecast than usual. When hurricanes get this far east (being ex-hurricanes by that point), they can change weather patterns – or exacerbate them. 2011 (I think) was a classic where two ex-hurricanes passed to our north-west bringing us that really hot September.

So…tell me something I understand

The general pattern for June will often see high pressure to our west, and also to our east over Russia – with us stuck in the middle, occasionally enjoying an extension of either high pressure, but low pressure dominating to our south.

June starts very warm (granted I’m writing this on 6th June so easy to forecast for the past). A northerly flow develops, bringing cooler and showery conditions for a while.

Exactly what happens after is uncertain, but rain or showers are quite likely in the second week or June – and rain bands could get stuck somewhere over England and produce some large totals of rain…but whether that is here or somewhere else I cannot know at this stage.

I feel that an easterly flow may develop before the middle of June – bringing warmth but an increased risk of thundery downpours.

Later in June looks more likely to be warm or very warm, perhaps even quite hot at times. Some good sunny days but I’m not expecting wall-to-wall sunshine and some thundery showers or even rain should be mixed in.

Certainly an interesting month, and watch out for the potential of flooding in France and/or Spain.

Overall I expect around average sunshine, somewhat above average temperatures. Low confidence on rainfall as it will depend on whether we get stuck under bands of rain in the second week of June, and any potential downpours.

Confidence level 70%.

July (I will write less, I promise), again looks quite a mixed month. There is a danger that I will get timings wrong on things here especially, but here goes.

There is a weak signal for something cooler and showery for the beginning of July again.

Otherwise July looks like a mixture of fine, very warm/quite hot sunny weather, with occasionally weak weather fronts from the north/north-west bringing some less warm conditions and a bit of rain/showers.

Towards the latter part of July, it looks like high pressure will be close to our east and low pressure close to our west – there should be some hotter and more humid days around, but also some wet days too, perhaps some thunderstorms.

Overall I expect slightly above average sunshine, above average temperatures and rainfall slightly below average – though catch a thunderstorm or two and it could locally end up well above average.

Confidence level 50%.

August now looks like high pressure will dominate to our east or over the UK and low pressure to our west. This distance away it is still finely balanced and I wouldn’t be surprised to see a wet August, but my forecast is for a sunny and hot August.

Yes, August I expect to be the best of the 3 summer months and I don’t recall ever forecasting that! Though I barely remember last week let alone every summer forecast I have made.

Often very warm or hot, good sunny days – occasional heavy, thundery showers developing some afternoons, though plenty of very nice weather.

Towards the end of the month, unsettled conditions arguably more likely as we head towards September – and the potential influence of La Niña.

Overall I expect above average sunshine, above or even well-above average temperatures and rainfall again more likely below average, but could be above locally if you catch some downpours.

Confidence level 60%.

Happy with that?

A brief look ahead to autumn – September looks more likely to be unsettled, otherwise there are no strong signals for the rest of autumn – a very weak signal for a drier than normal October.

I’m not thinking about winter until I know how the Quasi-Biennial Oscillation progresses.

Go on then – get sharing!

3 thoughts on “Seasonal Forecast – Summer 2020

  1. When you are talking about cool, warm, very warm, hot etc do you actually have specific temperatures, or even a range of temperatures in mind.?
    Love reading your predictions! Thank you

    1. Good question! I guess there would be a little seasonal difference in my definitions – in early spring I would probably call 15’C quite warm, but in summer I’d call it cool. Warm is roughly 20’C or above, very warm 23’C to 25’C, quite hot 26’C to 27’C, hot 28’C+, very hot 32’C+. Give or take but those are the rough values in my head.

  2. Thanks for that James, on the whole that looks very promising to me. Thank you for all the work you put into these forecasts especially this one.

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