Sunday 25th July 2021 -Thundery Downpour Chances

A more interesting day today than yesterday. Still lots of cloud around – there should be some brightness later in the morning, or early afternoon, which will only help to develop the downpours, though I’d fancy that there is enough instability and humidity to develop them even if it stays cloudy.

Scattered heavy showers, possibly with hail and/or thunder, could develop anywhere over south-east England, though I don’t think they’ll develop much further west than Reading, so it certainly could stay dry today.

Of more concern than scattered heavy showers, it does look as though there will be a zone of convergence, say 20-40 miles wide, roughly NE to SW, where multiple torrential downpours will likely develop this afternoon, with hail and especially thunder very possible. This would likely lead to flooding in places – a few spots could see some excessive totals of rain.

This zone appears more likely to be over London, but there is a plausible chance that it could be further west – or perhaps it develops over London and very slowly moves west later in the day/evening.

As always, plenty of uncertainty over the details – but worth mentioning the risk. Worth keeping an eye out on a rain radar, especially if you are out and about today.

Still warm and humid, reaching around 22’C, assuming the sun comes out for a bit.…

Saturday 24th July 2021 – Thundery Downpour Chances

So the forecast for today is a bit trickier and the chance of thundery downpours is lower than it looked a couple of days ago.

The early morning thundery rain has left a drizzly, cloudy overhang – and until this clears, storms will not be able to initiate.

There are signs of cloud breaking up on the south coast now, and these cloud breaks should spread north, though the longer it takes, the less likely there are to be storms developing – and it is certainly possible that cloud doesn’t break up until say around 6pm.

So the forecast really depends on how quickly the cloud breaks up and it feels more likely to stay cloudy until mid/late afternoon. I’d say therefore around a 30% chance of catching a downpour later this afternoon and into the evening, 15% chance of lightning – but if the sun breaks through in early afternoon instead of mid/late afternoon, the chance of a downpour will increase, as will the chance that it will be torrential with fairly frequent lightning – a very small chance of largeish hail too.

And if it stays cloudy until the evening, you may get a heavy shower but unlikely anything more notable.…

Thursday 22nd July 2021

I hope you enjoyed summer.

Low pressure will move up from the south-west for this weekend, bringing some downpours and possible thunder/lightning – then the jetstream sinks south next week bringing more changeable conditions – but still some pleasant, warm sunshine too.

Thanks to Chris for the photograph…had to go back a little to find something more appropriate!

Tonight will be another warm night though a little less so than of late, eventually down to around 16’C.

Friday will see more sunny spells, though hazy at times, especially in the afternoon – also some fair weather cloud bubbling up like recent days. Less hot, around 26’C and a bit more humid, but nothing excessive.

Overnight sees the start of the (possibly thundery) breakdown, as showers move up from the south. These kind of breakdowns are always difficult to get the details right – feasibly showers could be as early as midnight, but more likely say 4am onwards. Showers could be very heavy, thunder/lightning is possible though not an especially high chances, say around 25% chance. Also feasible that the showers don’t arrive until dawn.

So for Saturday, our developing low pressure is sat over the south of England.

Therefore we will see heavy showers throughout the day. Suggestions are that they are more likely early-mid morning, and again from mid-afternoon through to the evening (so lunchtime less likely) – but don’t take that as a guarantee as they could occur any time. Possibly very heavy, thunder/lightning could easily be in the mix too – showers could merge into longer spells of heavy rain. Still very warm, humid too, with a bit of sunshine in between showers then around 24’C should be reached. Showers remain possible overnight, down to around 16’C.

Low pressure is still in charge for Sunday. Lots of heavy showers, some very heavy/torrential downpours, hail and thunder/lightning all very possible, arguably even probable. Limited sunshine in between showers. Still warm and humid, around 22’C. Showers fading with clear spells overnight, down to around 14’C.

Monday is an improvement. Low pressure will still be close enough to the east to give a chance of heavy showers, say around a 60% chance so some places will stay dry. Sunny spells and fair weather cloud otherwise, and very warm, around 25’C. Clear spells overnight, down to around 14’C.

Tuesday again looks reasonable. Sunny spells and variable amounts of cloud, still the chance of a heavy shower, say around a 40% chance. Warm, 23’C. Clear spells overnight, down to around 14’C.

Details are uncertain for Wednesday/Thursday, but the general theme is that our weekend low pressure system will be circulating around the UK somewhere as an enlarged trough, with other low pressure systems being attracted to it’s circulation.

This will mean temperatures down to around 20’C or so – lower than average for the time of year, and with some showers or general rain at times, for both Wednesday/Thursday – though some dry spells too with fairly limited sunshine, but some.

Friday and into next weekend will depend on how the low pressure trough develops during the week, and where it situates itself. More likely it will be either over the UK or to our east, meaning temperatures below normal (though still warm given that it is late July) with further showers/rain at times.

There is a small chance instead, that it ends up to our west, and we drag some very warm/hot and humid air up from the south, but I rate it as a 10% chance. Still, 10% chances do happen occasionally.

The more likely outcome for next week is that the low pressure trough reloads from the west/north-west with further showery conditions to come, below average temperatures but also some sunny spells at times.

More likely we will have to wait until around 7th to 10th (ish) for the next build of high pressure and some general settled conditions with some warm sunshine. Earlier cannot be ruled out. Likewise, neither could a continuation of the changeable conditions further into August.

Of course, August brings the wild card of Atlantic hurricanes into the question, which can help over-ride the other factors that are causing my expectations of how early-mid August will play out.

Enjoy your weekend…I’m looking forward to getting back out and about once more after a weekend at home (yeah…I was pinged).…

Tuesday 20th July 2021 – Thunderstorms Update

My kind of day! I don’t know what the cloud is like in Reading, but in my corner of NW London it is certainly bubbling up.

Thundery downpours have broken out in a few places already, and will continue to do so through the afternoon and early evening. I do think the greater risk area is roughly between London and Peterborough (both for higher chances of a thunderstorm and higher chances of severe weather in a thunderstorm), but we are in the game also, and I’d still suggest around a 30-40% chance of a thundery downpour.

For the next couple of hours, storms will probably be quite brief – building up, then fading away very quickly. But later in the afternoon they should be able to survive longer.

Large hail, gusty winds, torrential downpours, flash flooding and frequent lightning could be in the mix, or any combination of those.

But remember, you are more likely to miss them and stay hot and sunny (with some gorgeous clouds) than to catch one – but catch one, and you’ll probably know about it!…

Monday 19th July 2021

Hot and sunny this week – with small chances of thunderstorms.

Thanks to Lee for the photograph.

Tonight will be a warm night with clear skies, temperatures eventually getting down to around 18’C, maybe 19’C.

Tuesday sees low pressure to our west and to our east – with high pressure sandwiched in between, but not the strongest build ever.

It will be hot and sunny in the morning, some cloud will bubble up in the afternoon and scattered thunderstorms will break out. I’d suggest around a 30% chance of catching one, and if you do it could feature torrential downpours, lightning – a small chance of hail and/or localised flash flooding. Many places missing them and will just stay hot with sunny spells. 31’C should be reached. Another warm night under clear skies, eventually down to around 19’C.

Wednesday will again be largely hot and sunny. Fair weather cloud will bubble up, one or two isolated heavy, thundery showers will develop but I think no higher than a 10% chance of catching one. Hot, around 30’C. Clear skies overnight, a tad less warm, eventually down to 17’C.

Thursday looks a bit less sunny than of late, but still decent sunny spells – just more fair weather cloud bubbling up. Still hot but a tad less, around 28’C. Clear skies overnight, down to around 16’C. A little high cloud spreading up from the south-west by dawn.

Friday sees sunny spells with variable amounts of cloud – sometimes rather cloudy, sometimes mostly sunny. High cloud will thicken during the afternoon making the sun hazy, as low pressure approaches from the south-west. Still very warm, around 25’C, likely somewhat humid too. Overnight (perhaps as early as late evening – timing is uncertain), a band of heavy, thundery rain will spread up from the south. Feeling quite warm and humid, around 17’C.

Saturday sees low pressure back in charge.

There may still be some heavy, thundery rain to clear in the morning – timing of the overnight rain is uncertain. This should clear north (not 100% certain – it could hang around) to leave sunshine and heavy showers. Kind of warm and humid, assuming some sunshine, around 23’C.

Sunday looks likely to be a day of sunshine and very heavy, thundery showers. Still a bit of uncertainty at this stage – I wouldn’t rule out general heavy rain, or dry with sunny spells. And temperatures around 22’C.

Next week is uncertain, though the somewhat more likely outcome keeps it changeable, with further heavy showers at times, perhaps general rain – but also some sunshine. Likely on the warm side.

We should return to something similar to this week, as we go into August.…

Monday 19th July 2021 – Small Chance Of Thundery Downpour

Morning. Another hot and sunny day today, we should reach around 30’C.

However, some cloud will bubble up this afternoon and isolated torrential downpours may develop. A bit of uncertainty over whether they will develop at all, but there is just about enough potential to be worth an update.

Around a 10% chance of catching a downpour this afternoon, with around a 5% chance of either lightning or hail. Localised flash flooding will be possible.

Slightly higher chances of a thundery downpour tomorrow.

You’ll have a full forecast this evening, but it will stay hot with sunny spells all week though gradually becoming less hot.…

Thursday 15th July 2021

Hot and sunny.

Honestly.

Thanks to Jonathan for the photograph.

Tonight sees cloud clearing, temperatures getting down to around 12’C.

Friday sees our high pressure nudge a bit further east, so we lose the northerly breeze which brought us lots of cloud in recent days.

Long spells of sunshine for most of the day, a little patchy cloud developing in places during the afternoon which will be hit and miss, some places seeing short cloudy spells, others staying glorious. 25’C, maybe 26’C. Mostly clear skies overnight, down to around 15’C.

Saturday again sees long spells of sunshine. A little bit of cloud bubbling up in places in the afternoon, but again hit and miss, some places staying glorious. Hot, 28’C feels realistic. Mostly clear skies overnight and a warmer night too, no lower than 17’C.

Sunday again sees long spells of glorious sunshine. A little bit of fair weather cloud possible and we should just about reach 30’C – which, if we do, I think is the first time this year? More in the way of cloud overnight so a warm night, around 18’C.

Monday sees our high pressure system a little to the north-west, which allows a weather front to scrape along the eastern side of the UK, bringing something a little fresher.

Still a reasonable day, a fair amount of cloud but also some decent sunny spells. One or two scattered showers will develop – they will be hit and miss but could be heavy. Still quite hot, around 25’C, maybe 26’C. Clear skies overnight, down to around 15’C.

Tuesday again sees sunny spells, but quite a bit of cloud developing especially around lunchtime/early afternoon. A small chance of a shower and still very warm, 24’C, maybe 25’C. Clear spells overnight, down to around 13’C.

Wednesday will see sunshine amounts increasing once more, and probably temperatures too. Still some fair weather cloud around but another pleasant day overall. Temperatures somewhere between 23’C and 28’C – depending on the position of low pressure to our west which could drag up something hotter – uncertain at this stage.

Uncertainty starts to increase from Thursday as a low pressure system to the west edges closer – which will determine temperatures and also shower chances in the latter part of next week and into the weekend.

More likely it stays sunny on Thursday, and very warm/hot – though I cannot discount thunderstorms or thundery rain arriving on Thursday or Thursday night.

More likely would be that thunderstorms or thundery rain arrives on Friday and staying showery for a couple of days after – but confidence isn’t especially high yet.

It should settle down again – I don’t expect this low pressure system to bring a change in the weather like the (non-thundery) low did in June at the end of the hot spell.

With plenty more fine, summer weather to end July and for a good chunk of August – though not perfect – not without showers/thunderstorms on a few days and temperatures will vary, sometimes warm, sometimes very warm/hot.

Enjoy the hot and sunny weekend, if you can. It feels like ages since I’ve been able to sit outside and have a beer on a weekend in the sunshine.…

Monday 12th July 2021

Summer’s coming home.

Really. It is. After the heartbreak of last night (at least for those reading who support England), hopefully the promise of high pressure building from the west during this week will offer some hope.

I have been expecting a switch to high pressure over or close to the UK to occur in the first part of July for some time now, it is a few days later than I previously expected, but we should this week switch to summer-like conditions for a few weeks – not perfect, not without showers at times, not glorious sunshine every day – but a big improvement from recent weeks.

And yes, I’m expecting to be too tired to do a forecast this evening, hence doing one now with the morning’s weather models instead of usual evening ones!

Thanks to Louise for the photograph.

We are not quite done with the unsettled weather yet – this afternoon will see heavy showers break out widely, hail, thunder and some torrential downpours all possible, and this will carry on through the evening. I’d be surprised if you missed them all, but feasible that you could stay dry and avoid them, highly unlikely though. Kind of warm and humid, around 20’C or a tad over. Showers gradually fading later this evening, variable cloud overnight, down to around 14’C.

By Tuesday we have our low pressure trough to our east, with high pressure starting to nudge in from The Azores.

Still quite a lot of cloud around, but there will be some sunny breaks – especially later in the afternoon. Still some showers developing, they could be heavy but some places will stay dry. Warmer, 22’C is likely. Clear spells overnight, though more cloud by dawn, down to around 14’C.

Wednesday looks like seeing quite a lot of cloud for a good portion of the day, but still some brightness at times and only a small chance of a light shower. Likely sunnier by late afternoon. Very warm, 23’C and breezy too. Clear spells overnight, down to around 14’C.

Thursday starts sunny but a lot of cloud will bubble up, and for a good portion of the day it will be mostly cloudy – only a small chance of a light shower. Again from around mid/late afternoon sunshine amounts will increase. Very warm and breezy, 23’C. Clear spells overnight, down to around 13’C.

By Friday high pressure is more dominant over the UK, and we lose the annoying northerly breeze of the previous days bringing the cloud.

And this means glorious sunshine all day. Yep. Maybe a little cloud at times, but the nicest day for some time – and reaching around 25’C. Clear skies overnight, down to around 14’C.

Saturday also sees long spells of sunshine. Maybe a little cloud at times, but overwhelmingly sunny and very warm, around 25’C, maybe a little more. Clear skies overnight, down to around 14’C.

Sunday again sees long spells of sunshine and very little cloud, if any. Temperatures nudging up to the hot category, around 28’C. Clear skies overnight and a warmer night too, down to around 17’C.

Next week will see high pressure remain in control, though the orientation is uncertain at this stage and this means whether it is glorious sunshine or there are some cloudy spells is uncertain, and also temperatures are uncertain – likely either warm or hot. Not expecting anything heatwave-like.

Chances of heavy showers/thunderstorms increases for later next week but that is very vague at this stage.

Broadly I do expect this high-pressure dominated scenario to last until at least early August, perhaps mid-August at a push. But as I mentioned in the introduction, it won’t always be glorious sunshine – there will be some cloud at times, there will be the odd weather front from the north-west bringing some rain and fresher conditions occasionally, and also the odd homegrown thundery downpour, more likely on hot days.

The chance of heatwave conditions is lower than recent summers, but is possible. Mostly I expect it to be very warm or hot during the next few weeks.…

Thursday 8th July 2021

The summer re-start has been delayed again thanks to another weak low pressure trough idling in from the west, but it is coming…summer will be coming…ho…no don’t say it. Way too obvious.

It does feel a bit like in May, where I could see the pattern change but it took longer (much longer in May) to arrive than expected. Although the weather for July so far does fit in reasonably well with my seasonal forecast – these delays to the restart of summer do make me nervous, yet I am pretty confident that next week will see the restart.

Alas, more showers to come first.

Thanks to Tara for the photograph.

A small chance of a heavy shower this evening, but these fading quite quickly – variable cloud follows with temperatures down to around 13’C.

Friday will see plenty more cloud but there will be sunny spells too, a bit more sunshine than recent days but still overall more cloud than sun. A chance of a shower in the afternoon, say around 30% chance and warm, around 21’C. Cloud tending to thicken overnight, some patchy rain arriving before dawn, down to around 14’C.

Saturday sees the next pesky weak low pressure trough arrive on the scene.

It starts cloudy with showery outbreaks of rain – it should be mostly light/moderate. Gradually during the afternoon brighter skies will push in from the west, though with one or two scattered showers. On the cool side for July, 18’C. Clear spells overnight, down to around 12’C.

It’s Coming Home Day looks rather cloudy with some occasional sunny breaks. Some showers also likely at times, perhaps heavy, but uncertain as to how widespread they may be – certainly could stay dry but I wouldn’t put money on it. Around 20’C. Showers or rain likely at some point in the evening or overnight – again uncertainty about timing and track on this – potentially heavy/very heavy and around 15’C.

Monday is uncertain due to the positioning of the low pressure trough, though it will be a more notable feature by this point. Likely unsettled, the question is really over whether it will be cloudy with spells of heavy/very heavy rain or sunshine and heavy showers – the former more likely. A small chance of thunder. Around 18’C, give or take. Showers or rain still possible overnight.

By Tuesday the low pressure trough will be over the east of the UK – though high pressure starting to nudge in from the west, helped along by ex-tropical storm Elsa to its north-west.

Details again sketchy for Tuesday – more likely a case of sunshine and heavy showers, but smaller chances of something drier and also smaller chances of more general rain. Around 20’C, perhaps a tad more.

By Wednesday, high pressure should be starting to influence a bit more, so it should be an improvement from Tuesday, but still good chances of a shower or three, and still likely plenty of cloud around, but some sunshine. Around 21’C.

Thursday should see high pressure just nudging a tad closer. Still a small chance of a shower, still plenty of cloud at times – especially the middle of the day, but warmer and a bit closer to what you might expect in summer.

By Friday, probably dry (no promise), probably more sunshine – but still a long way from glorious with plenty of cloud still likely to bubble up. And warm, around 22’C, give or take.

Next weekend should be dry and fine – sunshine amounts and temperatures are uncertain at this stage. Could be mostly sunny, could be mostly cloudy, could be anywhere from around 19’C to 27’C – all will depend on where high pressure situates itself.

I still expect most of the latter half of July, and first part of August to be broadly very warm/hot, decent amounts of sunshine – small chances of thunderstorms or the odd weak weather front spreading down from the north-west.

Next full forecast should be Monday, but who knows whether I’ll be capable after celebrating/commiserating the final of Euro 2020. Have a good weekend.…

Monday 5th July 2021

Some sun, some cloud, some showers and getting a bit warmer.  Not a summer classic, but it could be worse.

Thanks to myself for the photograph – I was just passing through though.

This evening sees rain spreading up from the south, heavy at times, especially around an hour either side of midnight, briefly dry before further heavy/very heavy showers push up from the south-west, a rumble of thunder possible. Quite windy, temperatures around 14’C.

Tuesday still sees low pressure in control, over the UK but starting to shift north.

Some sunshine at times, but plenty of cloud and lots of heavy showers, a rumble of thunder possible. Temperatures disappointing for July at around 19’C and windy for the time of year too. Showers less likely in the evening – but still one or two isolated heavy showers. Plenty of cloud overnight, a few clear spells, 12’C.

Wednesday will be similar, but a bit more sunshine and a few less heavy showers – yet still plenty of heavy showers around, and a rumble of thunder possible too. Showers tending to become less frequent later in the afternoon and in the evening, and less likely to be heavy. We should squeeze 20’C, maybe 21’C. Some clear spells overnight, down to around 11’C.

Thursday improves a tad more. Sunny spells, quite a lot of fair weather cloud around also, some scattered showers – some places will stay dry, others will catch one or more showers which could be light or heavy. Warm, 22’C – maybe 23’C. Clear spells overnight, down to around 13’C.

By Friday we are in this kind of no overall control situation which we’ve had a few times – which risks weak low pressure troughs developing – very similar to two weeks ago. Both the Azores High and Russian High are too far away to influence at the moment.

That said, Friday should be quite reasonable. Sunny spells at times, more likely in the morning – tending to be more cloud in the afternoon though how much is uncertain at the moment, perhaps rather cloudy if I’m forced to choose. Warm with a small chance of a shower, around 22’C, give or take. Rain possible overnight…

So as I mentioned, this no overall control situation may lead to another trough incoming for the weekend…joy. But at the moment this is uncertain, but a little more likely than not.

This would lead to some rain either Friday night or during Saturday – you can hope for Friday night, which would leave sunshine and showers for Saturday, though even Saturday morning rain would likely clear to showers in the afternoon.

Sunday would then likely be sunshine and showers.

So not the most amazing week/weekend ever for July and annoyingly uncertain for an important weekend, but also not a total washout either. Next week should see more influence from high pressure building from the Azores, though I feel like I said the same last Monday (I actually said it was too close to call).

I’ll be back on Thursday…well…depending on how much I celebrate/commiserate a semi-final.…