John Hammond’s Month Ahead – Heatwave to return? Will it or won’t it?

There’s been a lot of back-slapping going on in the world of weather forecasting. And why not? This summer’s hot and dry spell was correctly predicted by some long-range computer models several months in advance. On the face of it, they’ve been very impressive. Knowing their usual limited skill, I was certainly surprised by their ‘success’ this time – the heatwave was both more intense and more prolonged than I, for one, had expected. A quirky pattern of warm and cold water in the Atlantic is thought to have helped to build the dome of hot and dry weather that has for so long shielded much of northern Europe from the rain.

But was this skill or just luck? The truth is probably somewhere in-between. What forecast centres are being less vocal about now is how those very same models seem to have lost their touch. After the current ‘blip’ of cooler and damper weather, they have been predicting a swift return to very warm and dry weather through much of August and even into September as the jet stream’s path is once more blocked.

But with each day that passes, that signal seems to be retreating over the horizon. I’m not surprised. By definition, extreme spells are rare; and their continuation becomes less likely with time. As I’ve been suggesting for some weeks now, once the ‘block’ has been removed, it’s hard to rebuild it again – in the short term, at least. Here are my latest thoughts…

 

Mixture of rain and shine 

Blustery winds at times

Some lengthy dry spells

 

MONDAY 13TH AUGUST – SUNDAY 19TH AUGUST

From parasols to umbrellas (and back again?)

To get us in the mood, a low pressure area will wander in from the west through the weekend, to be sitting on top of us by Monday morning. This weather system contains some remnants of tropical air, bringing both the potential for some downpours, and also some muggy conditions. It’ll feel quite warm in any brief sunnier spells. (But Tropical Storm Debby is most definitely not about to batter us as some headlines would have you think).

In the wake of this system, we can expect a brief drier interlude as we approach midweek. With light winds, it’ll feel quite pleasant by day; but the nights will be quite cool.

We look to the west from midweek onwards, with further frontal systems set to bring more rain. The trajectory of these systems suggest that northwestern areas will see most of the wet and windy weather. Meanwhile the south and east will fair better, especially as the weekend arrives.

There should be some reasonable evenings at the Film 4 Summer Screen at Somerset House in London, but I’d take a layer or two for the cool evenings. Meanwhile at the Green Man Festival in the Brecon Beacons, you might want to pack a waterproof too – just in case.

 

Tropical Storm Debby is most definitely not about to batter us as some headlines would have you think

 

MONDAY 20TH AUGUST – SUNDAY 26TH AUGUST

Mixed messages

This is when things get, well, challenging. Many computer models are again trying to build higher pressure to block the jet stream’s path. This would begin to enable hotter and sunnier weather to become re-established, especially across the south and east of the UK.

I can’t dismiss this possibility. But as I implied earlier, this signal that has been ‘moving to the right’ on the timeline for some time now. Another factor which may complicate matters further is the possibility of ex-hurricanes or tropical storms injecting unpredictable ripples of energy into the Atlantic jet stream. Computer models struggle with these, even at much shorter time-scales.

All in all, I expect some lengthier drier and warmer spells for a time, especially across southeastern areas. But I don’t expect this to mark the beginning of another prolonged hot and dry spell. There will be further rain, most likely across northwestern areas. And thunderstorms may also threaten from the Continent later in the week. But for those going to both Carfest South in Hampshire and The Big Feastival in the Cotswolds, there’s enough evidence to suggest a ‘washout’ is unlikely.

 

Sticking one’s neck out is risky enough. It’s worse when there’s a Bank Holiday involved!

 

MONDAY 27TH AUGUST – SUNDAY 9TH SEPTEMBER

Heatwave Part 2?

Sticking one’s neck out is risky enough. It’s worse when there’s a Bank Holiday involved! There are so many events taking place – too many to mention. Fingers crossed for one of the most famous – Notting Hill Carnival! I continue to be sceptical about long-range predictions of a return to widespread dry and very warm weather as we arrive at the end of summer. Based on their lack of recent skill, Heatwave Part 2 seems unlikely to me.

Instead, I suspect that the likely blend of rather more mundane weather will suit most tastes. There will be some lengthy dry spells. But as occasional wet weather systems arrive from the Atlantic, we can hope for a continued slow recovery from the recent prolonged drought.

The shortening days bring a chill to the evenings as we head into September. As the holidays come to an end, I’m reminded that every day’s a school day in weather forecasting. It’s keeping us on our toes now, and will no doubt continue to do so as the Autumn term arrives.

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