This is an in-depth Met Office UK Weather forecast for the next week and beyond. It's turning warmer but will there be a heatwave? Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
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00:00It's turning drier, but will there be any further thunderstorms?
00:05It's also turning warmer, but will there be an official UK heatwave?
00:10Those are the two main questions I'm going to be taking a look at in this week's MetOffice Deep Dive,
00:15your weekly dose of in-depth meteorology.
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00:46Now, in last week's Deep Dive, Alex was talking about summer or the lack of summer,
00:53and he was on a mission to find it.
00:55Now, in this week's Deep Dive, I think I have found it, but it's not entirely plain sailing,
01:02and there are a few interesting things to consider in the next 20 minutes or so.
01:08For starters, let's take a look at the bigger picture and how we got here in the first place.
01:14We are currently below average in terms of June temperatures.
01:19Rainfall has been closer to average this month, but certainly temperatures at the moment for June so far
01:25have been running at about 2 degrees below average across the country.
01:28First 10 days of June, we had a cool northerly flow, and those winds straight from the Arctic persisting for quite some time
01:35brought some snow to the highlands of Scotland and also significantly below average temperatures.
01:41Now, we've lost those Arctic winds in the past few days, but we're still sitting to the north of the jet stream,
01:48which is normally a cool place to sit in the summer, and it's often a showery place to sit.
01:53So, as we've been sitting in this what we call upper trough, this kink in the jet stream,
01:59we've seen relatively cool air and frequent showers across the country.
02:04In fact, Tuesday afternoon, northern England, parts of the Midlands are directly under the axes of that upper trough,
02:11and that's why there's a thunderstorm warning for hit-and-miss downpours for parts of northern England and the North Midlands.
02:18But we're going to lose that upper trough over the next 24 hours or so.
02:25Watch as it moves away, and that's helped by this strengthening and slightly flatter jet stream coming out of the Atlantic.
02:33That's going to help to move along the upper trough, and as you can see, it pushes into Iberia and over the UK.
02:39Instead, we've got this ridge in the jet stream.
02:42The jet stream pushes to the north of the country for Wednesday, bringing fine, settled conditions for many.
02:47But that flatter jet stream, it's got some oomph to it, and it will bring some weather systems to northern parts of the UK,
02:56most notably northern Scotland, where we'll see some showery rain and some strengthening winds during Wednesday into Thursday.
03:04And then another low turns up with, again, this pulse in the jet stream, bringing that low to the north of the UK
03:12and sending a couple of weather fronts in as we end the working week.
03:16So some rain into western parts as we begin Friday.
03:19As that crosses the country, it tends to weaken, and by this stage already, the jet stream's taking another slightly different shape.
03:29It's again flatter than it has been, but it's also starting to push to the north of the UK.
03:36Good news if you're looking for summer weather or at least something a little more settled, drier and warmer,
03:42because as that jet stream pushes to the north of the UK, we're now on the warm side of the jet stream.
03:47We're also seeing the influence of higher pressure building in from the Azores.
03:51This is called the Azores High, and that's because it typically sits near the Azores.
03:56But in the summer, if it extends towards the UK, that's when you can get widely fine and bright and warm weather across the country.
04:05So through the next few days, the jet stream is changing shape.
04:10It's becoming flatter, which helps to push that upper trough away, taking the showery conditions with it.
04:16But it's also then eventually moving to the north of the UK to allow more widely settled and warmer weather.
04:23Let's just take a quick look at the day-to-day detail, because there will be some things to talk about each day.
04:29Now, for the rest of Tuesday, as you can see, northern parts of England into the north midlands subject to quite a few showers.
04:36But as that upper trough moves away, here's the picture for Wednesday.
04:41Widely fine weather. However, that flatter jet stream, as I mentioned, just to the north of the UK,
04:48is going to send some showery rain into the northwest of Scotland and some strong winds as we end Wednesday.
04:54But by the time we go into Thursday, that's moved out of the way.
04:57This is the start of Thursday. As you can see, widely fine weather across the UK.
05:01Some patchy cloud here and there.
05:03What was the chance of the odd shower into the far south?
05:08And actually, what you can see there near Paris are some very lively showers later Thursday.
05:16And moving up to the low countries into the start of Friday. More on that in a moment.
05:21So don't go anywhere if you want to find out a bit more about those showers and thunderstorms.
05:26Otherwise, for most of the UK, it's fine on Friday at first before the cold front that I mentioned.
05:31That's coming into the west. Thickening cloud, outbreaks of rain.
05:34And as that crosses the country on Saturday, it turns to showers and it's a relatively weak affair.
05:43So, yeah, it's mostly settled picture over the next few days.
05:47But there are some showers to think about and also some patchy cloud and a breeze in the far north of Scotland.
05:57Now, those showers and thunderstorms that I mentioned over the continent are most likely to stay away from the UK.
06:04But it's not a guarantee. Let's take a look at that again from the bigger picture.
06:11We've got that upper trough that I mentioned. It's being pushed away.
06:14But as you can see, later Wednesday, it's digging down over Iberia.
06:19And if we put the rainfall on, you can see it's causing an awful lot of showers and thunderstorms over initially Iberia.
06:26And then this showery activity starts to move up.
06:29So that's Thursday. Chances of showers in the far south.
06:32But watch this clump of showers moving north eastwards across France into central Europe.
06:42And it's associated with this flabby area of low pressure.
06:46So the ingredients there, not only do you have the jet stream intensifying this area of low pressure and some heavy rain, some thunderstorms.
06:55You've also got a marked temperature contrast, some heat across central parts of Europe colliding with cool air across much of France and the UK.
07:05Now, the Met Office model is sending that rain away from the UK.
07:12It's moving north east across central parts of Europe. And in fact, the European model has the same idea.
07:19So this, it might not look too clear on the screen there, but basically this is the UK right here in the middle.
07:28And this is Denmark. And just south of Denmark, we've got the area of low pressure I mentioned there.
07:35And that's in roughly the same place on the European model. That's what this is showing as the Met Office model.
07:40So that's in agreement. But we don't just run these computer models once.
07:46We run them lots of times. And one of the simulations of the European model has that low pressure much closer to the UK.
07:56So there it is in two parts of East Anglia and the southeast.
08:01And in fact, when we run the Met Office model lots and lots of times, here's just a selection of those different computer model runs with each run showing different rainfall distribution here on the screen.
08:15These are known as postage stamps for obvious reasons. And the UK is somewhere in the middle.
08:19Might not be that obvious on the screen, but just want to point out that there are a couple of these runs that have some heavy rain of East Anglia in the southeast.
08:27For example, this one, number 31, number 26 here has some white colours across East Anglia in the southeast, which would indicate 32 millimetres or more in the space of six hours.
08:39Most of these don't have any rain at all over East Anglia in the southeast, but a few of them do.
08:46So it's an idea that we can't entirely discount from the computer models.
08:50In fact, as I mentioned, the Met Office main model run doesn't have any of that rain or the thunderstorms across the southeast on Friday.
08:58Neither does the European model run, but the American main model run does.
09:05And this shows the rainfall totals from each of those simulations.
09:09This is the Met Office on the left, the European model in the middle, and this is the American model on the right.
09:16And this shows the amount of rain we're expecting to accumulate between now and Sunday night.
09:23And what you can see is very little rain across eastern England, for example, between now and Sunday night.
09:31And the Met Office model on the left, a fair amount of rain there across western Scotland.
09:35That's where those weather fronts will be moving in from the northwest.
09:39But the European model also very similar.
09:42So most of the rainfall there, northwestern parts of the UK, a few showery outbreaks, perhaps for the south, but very little for the east of England.
09:52By contrast, the American model, which had those thunderstorms just further west to affect east England and the southeast, has 50 mils or so between now and Sunday night.
10:05And most of that 50 mils, incidentally, would be falling in a few hours on Friday morning.
10:11So what we reckon at the moment, looking at all this different model output, is that there's an 85% chance that those thunderstorms will miss the southeast on Friday.
10:22But there's a 15% chance that those thunderstorms will hit east England and the southeast.
10:27And it's a chance that we can't entirely discount.
10:30And it's a chance that would be very impactful, 50 millimetres of rainfall or more falling in the space of a few hours.
10:37So certainly something to keep in mind.
10:39Hopefully, we'll have a bit more clarity over the next 24 hours when more computer model runs come out.
10:45So that's Friday's rain.
10:47The other main talking point this week and into next are the temperatures.
10:52So let's just take a look at that.
10:53As I mentioned, the jet stream is going to be moving to the north of the UK.
10:58And actually, not only have we lost that Arctic wind, but we're also going to be sitting on the other side of the jet stream, the warm side.
11:07So naturally, we're going to see sunnier skies and we're going to see rising temperatures as a consequence.
11:14What does that look like on here?
11:18We skip to day three, for example.
11:21This is Thursday, skip to day four, Friday and day five, Saturday.
11:27And you can see some warmth starting to appear from the west as that higher pressure begins to arrive.
11:34These orangey-red colours.
11:36So as higher pressure moves in, we'll get more sunshine, but we're also importing warmer air from the southwest at the same time.
11:43Now, temperatures at this stage won't be extraordinary.
11:46Sure, on Thursday, Friday, Saturday, Sunday, we could see temperatures exceeding the highest temperature of the year so far, which is something like 27.5 degrees.
11:56But we're not looking at temperatures into the 30s just yet.
12:00And just to give you an indication of how those temperatures will rise, I'll just get my pen over here.
12:05There we go.
12:09I'm just going to draw a little line across the country and you'll see how the temperature trend will vary.
12:16Now, this is, for example, in the Midlands.
12:19We're looking at high teens later this week into the low 20s by the weekend.
12:25Southeast, 23. It's showing 23 there.
12:29This is the raw computer model output.
12:31You could probably add a couple of degrees or so onto this, given optimal amounts of sunshine and light winds and so on.
12:40But you can see a clear temperature trend upwards later this week and into the weekend.
12:49But at the moment, as I say, temperatures up to the mid to high 20s in some of the spots, some of the warmer spots through the weekend and early next week.
12:58Just for a bit of comic relief, I don't know if you saw this headline.
13:01It kind of went viral from the Daily Mirror.
13:03UK to be blasted by 48-hour 26C heatwave with five cities in England the hottest.
13:10This forecast, incidentally, didn't really come from the Met Office, as was put out last week.
13:16But a lot of people found it amusing that 48 hours of 26 Celsius was considered a heatwave.
13:23As you can see by some of the comments from people in Australia and Louisiana.
13:30You're all weak, that person says.
13:34But obviously, the definition of a heatwave is going to vary from place to place around the world.
13:41What would be considered a heatwave in Iceland would be very different to Louisiana and Australia.
13:46And it is indeed different to what's considered a heatwave in Scotland compared with the southeast.
13:54And this is the official Met Office heatwave definition.
13:58And basically, for Met Office purposes, a heatwave is declared if the temperature exceeds a certain temperature.
14:09Three days in a row. So the maximum temperature has to exceed a certain temperature three days in a row.
14:14And that temperature for most of the UK is 25 degrees.
14:18Scotland, Northern Ireland, Northern England, Wales and Devon and Cornwall, for example.
14:22Then you get into the Midlands and central southern England and it's 26 degrees.
14:28And then across much of the rest of the Midlands, East Anglia, the southeast, it's 27 degrees.
14:33Except for London and some of these counties to the north of London, Cambridge, Hertfordshire and so on, where it's 28 degrees.
14:39This is obviously based on what we're used to climatologically.
14:43These are hotter places in the UK, typically in the summer.
14:47And so the threshold is slightly higher.
14:50But you'd have to exceed those values three days concurrently.
14:54And 28 degrees from London to 25 degrees for Scotland.
14:59So the question is, as temperatures rise into the start of next week, are we looking at an official heatwave?
15:04And the answer is, it's complicated.
15:07Let's take a look, first of all, at the probability of 25 Celsius or above.
15:14And this shows each day, taking the European model, all those 52 computer model runs.
15:19And it shows the probability from all those different simulations of exceeding 25 Celsius each day.
15:26This is Tuesday 18th, this is today, this is Wednesday, tomorrow, and then up to Saturday.
15:31All these maps are white, basically.
15:34Although I would say there is a chance, certainly in some spots on Thursday, Friday and Saturday, of exceeding 25 Celsius.
15:41But by the start of next week, we're getting these colours appearing on the maps.
15:46And certainly on Monday, Tuesday, Wednesday, the colours become a little darker.
15:53And that just suggests that through Monday, Tuesday, Wednesday, the chances of exceeding 25 Celsius are greater.
16:02And what we would suggest is that certainly it looks likely, as that azores high builds, as the jet stream sits to the north of the UK,
16:11that we'll see quite widely across England and Wales temperatures of 25 to 27 or 28 Celsius for at least two days at the start of next week.
16:21Say Monday, Tuesday or Tuesday, Wednesday or so further north.
16:25Widely settled weather, as to be said, but not as hot across Scotland and Northern Ireland.
16:30We're looking at low 20s more widely.
16:34But then the probabilities just ease off there for Thursday.
16:41And if you were to look at the main operational run of the European model, you could see why.
16:48This again is showing the UK about here.
16:53And this is the forecast from the high resolution run of the European model for Wednesday, the 26th of June, around midday.
17:01And this has got that azores high just further west again.
17:04It's moved it to the west and it's got this blue line across southern parts of the UK.
17:09That's a cold front with a northerly airflow behind it.
17:14So bringing those temperatures back down again after a couple of days of warmth and then it keeps things cool for the rest of the week.
17:24But when you compare that with what the other simulations from the European model are suggesting, it's quite interesting.
17:33Now, just this top chart here, this is, again, the European model output and it shows the temperature trend.
17:40This shows it at 5,000 feet or so, but that's quite a useful place to look at the temperature trend because it smooths out those day night differences and any differences to do with mountains and coasts and so on.
17:51So it just shows that temperature trend and it's an upward trend.
17:54If you look at the solid line in the middle at first, it's an upward trend into the start of next week and then peaks on Tuesday.
18:02This is the main high resolution model run from the European model, then takes this nosedive back down to current levels.
18:10So the heat peaks on Tuesday. But all the other dotted lines on this chart show all the other simulations from the European model run.
18:21And a lot of them are to the higher end of that chart.
18:27So they keep things warm. They don't peak on Tuesday and then bring them back down.
18:32They keep things warm Wednesday into Thursday and some of them go even higher.
18:37Now, what this suggests is that the high res model run is actually a minority outcome in terms of the 52 simulations.
18:47It's a bit of an outlier. And many more of the simulations keep the warmth across the UK.
18:54This is Reading, by the way, in the south of England. And some of them even push it even higher.
19:01So there's a slim chance that temperatures will get into the low or even mid 30s if some of these warmer simulations were true.
19:11But most of them keep things in the mid to high 20s throughout next week.
19:16It's just that operational run that has things cooling off once again.
19:20And just to show you that that's the case for the whole of the UK, this is Glasgow.
19:25And it's even more stark here, actually. It's got that nosedive around Wednesday as those northerlies appear in the operational run.
19:31But the darker colours here just show that grouping of all the other simulations that keep things warm.
19:39So what do we do when we're faced with that information?
19:43We'll look at the reasons why. And this, again, is the high res run from the European model.
19:49But just to give you a sample of what the other simulations are saying and why there's this disparity, here is Member 22.
19:57It's similar to the high res run. It's got the cold front to the south of the UK. It's got northerly winds.
20:02But there aren't that many out of the 52. There aren't that many that look like this.
20:07Some of them look a bit like this. There's the UK and there's low pressure over France.
20:12And that would suggest warm and perhaps thundery across southern parts.
20:17Again, high pressure sitting to the west. This is a relatively minority idea.
20:22The most common theme is this sort of thing. I know it's quite complicated with lots of red and blue lines on them.
20:29These are weather fronts. But the basic idea from this is that high pressure, instead of sitting to the west of the UK,
20:36it pushes to the north and allows this southeasterly airflow across the country.
20:41And it keeps the warm plume in place for Wednesday and beyond that into Thursday and Friday.
20:47So this is Member 29. Member 30 shows a similar sort of thing. Higher pressure moving to the northeast and allowing the warmth to arrive from the southeast.
20:55So what this suggests to me is that it all depends on where that high pressure ends up.
21:02And just to give you an idea of the three most likely pressure patterns for the middle of next week.
21:11This looks not just at the European model, but the Met Office model.
21:14The American model takes all those model simulation, dozens and dozens of them.
21:18And it comes up with likely scenarios for the middle of next week.
21:24And the most likely or the joint most likely is for higher pressure to be sitting over the UK, keeping things relatively warm, dry and sunny for many places.
21:35But also in that top likelihood category, 19% chance, joint most likely, is for the higher pressure to sink or to push to the northeast of the UK.
21:47And this warm plume, so temperature anomalies, that's what these are showing, 2.6 Celsius there in the south, 1.7 Celsius compared with average across Scotland, for example.
21:58This is also 19% chance, same as the other one. A less likely chance, this is a 7% chance, is for the higher pressure to push to the west.
22:07And for this colder northerly flow with temperature anomalies of minus 1 Celsius compared with climate.
22:14So that main run of the European model is looking less likely than other output, which suggests that we'll keep the warmth for more than a couple of days next week.
22:25Either way, the signals are relatively weak.
22:31This shows the probability of either northerly or southerly winds.
22:37So this shows on the top row there, the most recent model output on each date going forward out to the next two weeks.
22:46So the final column is 2nd of July. If the boxes are coloured red, it shows that southerly winds are more likely than northerlies.
22:56And if the boxes are coloured blue, northerly winds are more likely.
23:00And it's showing quite strong reds through the weekend. That's what this is showing and into the start of next week.
23:06Then the reds get a little bit more faint from the middle of next week and then sort of disappear altogether.
23:12But what that does suggest is that southerly winds are slightly more likely than northerly winds, but certainly not a guarantee.
23:19And it's an increasing trend when you look back at previous model runs for those reds to become slightly more dominant.
23:27We've got a similar sort of chart here and it shows the likelihood of higher pressure or lower pressure.
23:33So in this case, higher pressure is coloured in red.
23:36And what this shows is that through next week, we've got the reds.
23:40Higher pressure is a little more likely than lower pressure.
23:44But certainly those reds aren't dark enough for us to say it's definite.
23:50So all in all, what we're looking at through next week is an extension of the Azores high, widely dry, settled and increasingly warm weather.
24:01Most likely temperatures in some of the warmer spots in the south, mid to high 20s, low 20s elsewhere across the UK.
24:07And then the potential for that higher pressure to move away around the middle of the next week.
24:14But where exactly it moves will have a big effect on how high the temperatures will be.
24:20Will it turn cooler as the high moves to the west?
24:23That's looking slightly less likely than the high pressure moving to the north or northeast and allowing the warmth to continue to arrive from the south.
24:34Either way, higher pressure doesn't seem too far away from the UK, so it's likely to say mostly settled.
24:41But of course, this time of year, you couldn't rule out thundery downpours whenever you've got heat in the mix.
24:48So I hope all that made sense. Of course, Glastonbury is coming up as well.
24:53And as I say, conditions look mostly settled at first, but the signals are weak.
25:02So we'll keep you updated right here.
25:05We'll look at all the different output every day and we'll hopefully be able to give you a clearer forecast in the next few days and so on.
25:14But I hope you enjoyed it this week. That's all from the Metal Viz Deep Dive.
25:18Don't forget to hit subscribe, hit like and send us a comment, send us a question. Bye bye.