- 5 months ago
This is an in-depth Met Office UK Weather forecast for the next week and beyond.
Bringing you this deep dive is Met Office meteorologist Alex Deakin.
Bringing you this deep dive is Met Office meteorologist Alex Deakin.
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00:00A red warning for extreme heat, record-breaking temperatures and a thunderstorm sandwich.
00:07It's all in this week's Met Office Deep Dive.
00:10There is plenty going on, plenty to talk about, as always,
00:14but this week is going to be pretty remarkable in terms of temperatures in particular.
00:18Welcome along to the Met Office Deep Dive.
00:20My name's Alex Deacon. We do this every Tuesday.
00:23Today we chat through in detail what's going on in the skies and in the atmosphere for 20 or 30
00:30minutes or so.
00:31It might be a bit longer this week because, as I say, there's plenty to talk about.
00:35Do let me know in the comments if you are enjoying this Met Office Deep Dive.
00:40If you've got any questions, pop them in the comments as well.
00:43Do hit the Like button. Do us a favour and spread the love as well.
00:47I'll let everyone know the Met Office is on YouTube and doing this kind of broadcast every week.
00:54Let's, before we get on to the temperatures, let's deal with the crash-bang wallop of Monday night and the
00:59thunderstorms.
01:00Here is some beautiful imagery of the storm that hit the southwest of England.
01:05You can see that's Devon and Cornwall poking out there.
01:08That's Wales there.
01:10And this storm that generated through yesterday afternoon caused some fantastic imagery, but also caused some significant flooding and lots
01:21of flashes of lightning.
01:22Now, this is what's called a sandwich image because it's a combination of the visible from the MTG satellite and
01:31also the infrared.
01:32That's what's providing the colour layers.
01:34That's been enhanced with colour layers for the infrared imagery over the top of it.
01:39You can see that cell developing really rapidly through the afternoon, expanding and then moving its way away to the
01:46east.
01:47Really interesting and highlighted to me by Neil Armstrong, one of our chiefs here at the Met Office.
01:53That was one storm.
01:55We then had another clutch of storms through the early hours affecting the London area.
01:58So this one kind of dissipated as it moved off and then another batch of storms brewed up in and
02:03around the London area through the early hours.
02:05But this one was particularly interesting.
02:07It kind of developed through the middle of the afternoon and you can actually see the overshoot here in the
02:13centre of the storm.
02:14You can see where it actually shoots up through the top of the troposphere.
02:17What am I talking about?
02:18Well, the troposphere is the bottom part of the atmosphere.
02:21That's where all the clouds are.
02:23That's where the weather happens.
02:24You do get some a little bit higher, but that's where all the weather happens in this bottom part of
02:28the atmosphere.
02:29And this yellow line is tracking the temperature as we go all the way up through the stratosphere, the mesosphere
02:34and the thermosphere.
02:35So generally in this bottom part of the atmosphere, the temperatures go down.
02:39So as you go up through the sky, it gets colder until you get to the top of the troposphere,
02:45the tropopause, and then actually get a change in the temperature.
02:48So actually through the stratosphere, temperature actually starts to rise again as you go through here.
02:53So we get this what's called a temperature inversion, and that's what keeps a lid, if you like, on the
02:57bottom part of the atmosphere.
02:58That's what keeps a lid on our clouds and why they generally stay down in this bottom part, because we
03:05have this temperature inversion.
03:06So the cumulonimbus cloud, the thunderstorm cloud, bubbles up.
03:10It goes all the way to the top of the troposphere, and then it generally stops.
03:13However, if it's got enough welly, enough energy from the updrafts causing the thunderstorm, well, it can pop through.
03:21So it goes through the top of the tropopause and into the stratosphere.
03:26So it does, at times, you do get these kind of explosions through the top of the troposphere.
03:30So instead of getting that flat anvil spreading out from a cumulonimbus cloud, you do get them popping up through
03:36the top.
03:37And you can see that on the imagery here that we saw from yesterday's storm, this darker circle in the
03:41middle.
03:42And really interestingly, it might not be that clear in this image, but I think you can make out these
03:45concentric circles coming out from the middle of it.
03:50That's caused by gravity waves.
03:52So, again, highlighted to me by Neil Armstrong, our chief here at the Met Office.
03:56You can see where the center here is.
03:57It's popped out.
03:58It's gone up through, then into the more stable part, the stratosphere, and it's dropped back down.
04:01So it then spreads out as a wave, like a pebble, dropping into the middle of a pond or a
04:08lake.
04:08You get this spreading out effect, that ripple effect, and they're called gravity waves caused by an anvil popping out
04:18the top of a cumulonimbus cloud.
04:20So you can see that quite clearly there.
04:22Really quite interesting, I thought, from one of yesterday's storms.
04:25Let's catch up on the other ones because it wasn't just across the southwest where we saw the storms yesterday.
04:32And this is showing the lightning flashes from yesterday afternoon into yesterday evening.
04:37So there's that first batch, and then we get another batch down here as we head through the night into
04:41the early hours.
04:42So if you're in the southeast, you may have got woken up by that set of thunderstorms.
04:48So let's take a closer look at that, and let's take it back to the afternoon.
04:52You can see the little clutch initially over Cornwall, then through Devon.
04:55Whoa, then it really kicked off, and then it died down again.
04:59And then as we went through the early hours, we got another batch in this zone just to the north
05:03of London.
05:04Then it moved through the London area, and we've still had those thunderstorms rumbling on even into the morning across
05:09parts of Kent.
05:09So really remarkable.
05:11Let's put a little tilt on that.
05:12You can see them better there as they crossed through, almost through the spine there, across Devon and Cornwall, up
05:17through the higher ground, perhaps sparked off by before they're moving through.
05:21And then you get this next batch coming in and around the London area.
05:24Twenty-nine thousand lightning strikes, we think, across England through the course of the night.
05:32I counted them all myself.
05:33But that's what we reckon.
05:35Twenty-nine thousand as those couple of storms moved their way through and continued into this morning.
05:41So, yeah, some thundery activity, to say the least, last night.
05:45Been a bit calmer today.
05:47But, of course, the residual moisture from those thunderstorms did have an impact on today's weather.
05:54Created a bit more haziness and took a bit more energy for the sun to work, to lift the temperature.
06:01So a bit slower taking off as we've been through the day today.
06:04But temperatures, definitely the story over the next few days.
06:09Well, as they have been for the past few as well.
06:11This is the bigger picture.
06:13This is what's happened over the course of the weekend.
06:15You can see this dip here, almost, in the higher cloud because of the jet stream, which has been dipping
06:21down to the south and pushing up to the north.
06:23And that's been allowing the warmer air to waft up.
06:26The heat's been in place across France for a number of days.
06:29We've had this kind of high-pressure heat dome, if you like.
06:32That's been there.
06:33That's been building record-breaking temperatures across parts of France.
06:36And increasingly, we've seen this dip.
06:39Let's put the jet stream on, actually.
06:40It's probably the best way to show it.
06:41We've seen the dip in the jet stream out in the Atlantic.
06:44And that is going to get more exacerbated over the next day or so.
06:48So the jet is dipping down to the south and up to the north, and that's allowing, under this upper
06:53ridge, the high pressure to sit in and around the UK.
06:56The high pressure is squashing the air, so the air is getting squished down.
07:01That is what's allowing the temperatures to build day on day.
07:03Also, you know, drawing in the air from the south and from the east, which is lifting the temperatures.
07:10The sun is high in the sky.
07:12It's the compression from the high pressure plus the heat from the sun that's gradually lifting the temperatures day on
07:18day.
07:18And we're seeing hotter air just gradually trickle its way northwards day on day as we go through this week
07:23until at least Thursday, which is likely to be the peak in the temperature.
07:28So high pressure here.
07:30There's the jet pushing its way southwards.
07:32And if we continue, see this dip down in the jet stream.
07:35It's continuing even into Thursday afternoon.
07:38And that's allowing that high again to sit in here.
07:40Let's put the temperatures on and that's drawing up that heat, that excess heat.
07:45And that's when we're going to see the peak probably through the course of Thursday afternoon and into the evening.
07:50So temperatures will continue to rise over the next few days.
07:54Just going to show you now where our air is actually coming from.
07:57I'm going to show you the trajectories of where the parcels of air are coming from, because that's really important,
08:02because this isn't just hot air that we're seeing.
08:05It is quite humid as well.
08:08And that is vital in terms of the impacts that it has.
08:12The more humid air, the way that you sweat, the way that the body loses heat or regulates itself is
08:18by sweating.
08:19And if the air around us is more humid, it makes it that much harder to sweat.
08:24So the humidity is a key factor in this heat wave, not just how high the temperature is going to
08:30be, but the longevity of the heat, the fact that it's sticking around overnight and the fact that it's going
08:35to be humid, more humid than in 2022.
08:38So the last time we saw temperatures over in the high thirties and the only time we've seen temperatures over
08:4440 degrees, 2022, the all time temperature record broken in July of that year.
08:50I'm going to show you where the air came from on that day.
08:54So these are the back trajectories tracing back the air, but this is going back in time.
08:59We're going back to 2022 and this is showing where the air parcels have come from.
09:04So the UK is under there. If we just play this forward, actually probably have a little closer look at
09:09this so we can, the UK is under there.
09:11There's a map of Europe. So the UK is under there. There's Ireland, Northern Ireland, Scotland under there as well.
09:17And then England or Wales under there. So this is tracking back the air to Lincolnshire where we have the
09:21top temperature.
09:23This is a profile, this one here, the height, how high up the air has come from.
09:29And this is time going along the bottom here.
09:31So this is going back in time and we're tracing the air to the bottom 1000 metres, the bottom kilometre
09:39at the time that we broke the temperature record back in 2022 in Lincolnshire.
09:43So the yellow lines is the air at the top of that one kilometre and the dark blue purple lines
09:50is the air at the surface where we experience it, where the thermometer was as well.
09:54So the dark blue lines, that's the temperature right at the surface, the yellow lines is the air about 1000
10:00metres up and then goes down through the greens, which is in the hundreds of metres.
10:06And it's tracing where the air has come from. So you can see that the air actually originated across North
10:10Africa that was a kilometre up in the sky when we broke the record.
10:15But the air at the surface back in 2022 actually originated up here.
10:21So you can see that the temperatures, the air is coming from the temp, from Greenland and across into Iceland.
10:29So the air originated from a cooler source and a drier source as well.
10:35So actually in 2022, the humidity wasn't that high, the dew points weren't that high.
10:40If we fast forward and show you the profile of what we're expecting this Thursday in and around the London
10:45area, you can see the trajectories are very different.
10:49You've still got the yellows, which is at the top of that kilometre line coming from North Africa and some
10:54of the greens as well.
10:55But the darker blues, the air that's going to be at the surface on Thursday has come from the Atlantic,
11:03from down to the southwest of the UK.
11:05So that is important because the source of the air is not only a little bit hotter than it was
11:10back in 2022, but it's also going to bring more moisture with it because of where it's coming from.
11:14It's coming from over the Atlantic. So it's moist, warm air that's coming, getting compressed, traveling around.
11:21And then that last bit gets drawn around from across France, where we've seen the high temperatures at the moment
11:28before it gets drawn in and around to the London area.
11:30So that's a key difference. That increase in moisture means we'll feel the humidity more and that is likely to
11:37have more health impact.
11:39So although we may not realize, not ruling it out, but the moment, the most likely temperature is 38, 39
11:45for the peak on Thursday.
11:47But the humidity is going to be higher than it was back in 2022, which has greater health impact.
11:53Let's take a look at the temperatures now, then, and what we are expecting over the next few days.
11:59These are the maximum temperatures. So today we're struggling to get up there, but at 33, 34, 35, possibly.
12:07Wednesday more widely in this zone across the Midlands, Southern England, 35, 36, 37, or perhaps the 38 in and
12:14around the London area.
12:15Thursday could see that heat pushing a bit further north into Northern England, 34, 35, and then into the Midlands.
12:22We've got 38, and in this zone again across the Midlands, Southeast Wales, into the London area.
12:27That's where we could see 38, maybe 39 degrees Celsius in this zone here.
12:33Cooling off? Not really.
12:35In the east temperatures again, 35 at least, perhaps even a little bit higher.
12:39So we're delaying the onset of the slightly fresher air.
12:43Certainly in the west, temperatures won't be as extreme by the time we get to Friday,
12:46but we may well linger into this extreme heat in the east, even into Friday.
12:51So that's the air temperature, but I wanted to show you something else now, the dew point.
12:59As we go through Thursday and into Friday, now, going back to those trajectories, back in 2022,
13:05the dew point was around about 8 or 9 degrees, whereas now, if we look at Thursday, take off.
13:13The cloud and the rain.
13:15What we're expecting in terms of the dew point is something closer to, oh, is it going to work?
13:21Yeah, there we go.
13:2218, 16, 17, further south and east.
13:25We're looking at these dew points.
13:27The dew point is the temperature that you have to reduce the air to to make it saturated.
13:34So if you have the same body of air, if you take the temperature down, what temperature would it be
13:39saturated at?
13:40And that gives you an indication of the humidity.
13:42So if we took that air that's sitting across us on Thursday and took the temperature down,
13:47it would it would be saturated in the high teens or perhaps even the low 20s in places.
13:52So that is indicative of how much more moisture there is in the air this time around compared to 2022,
13:58which is why we're more concerned about the health impacts,
14:01which is why we've got the warnings in place across England and Wales.
14:06So this is the amber warning in place for today.
14:11It was in place yesterday and today covering large parts of England and Wales.
14:15Temperatures likely getting up into the low to mid 30s.
14:19But by the time we get to tomorrow, we are expecting, particularly in this zone,
14:23with that combination of humidity and high temperatures,
14:27to see temperatures getting into 37, 38 degrees, maybe 39 on Thursday in this red warning zone.
14:35So in that red warning zone, I say there's the humidity,
14:39the fact that it's going to be long lived for three or four days and the nighttime minima.
14:45They're also playing a key factor.
14:47Also, we had a tropical night last night.
14:49Temperatures where temperatures stay above 20 Celsius.
14:52That's the definition of a tropical night and record breaking in Wales,
14:55the warmest June night on record in Wales.
14:57And for the next few nights, we are likely to see those temperatures again,
15:02staying up in the high teens or potentially into the low 20s of Celsius.
15:08That is here.
15:10This is the chance of having a tropical night on Tuesday night into Wednesday morning.
15:17Across the south, the chance of a tropical night.
15:20Sorry, this is Wednesday night.
15:21Chance of a tropical night on Wednesday night.
15:22So the probabilities up in this zone here from Lincolnshire down to southeast Wales
15:30and across to the southeast corner,
15:32that's where we're most likely to have temperatures over 20 degrees Celsius.
15:35And the chance is, what, 60 to 80 percent.
15:38But we keep the warmth over the next few days and nights.
15:42And if anything, it gets a bit hotter by the time we get to Thursday, Friday night,
15:46that warmth continuing across the southwest for Thursday night and into Friday.
15:50And then Friday, again, the probability of keeping temperatures over 20 Celsius,
15:57particularly in that southeastern zone,
15:59so that the air is just shifting around a little bit more to the southwest Thursday night,
16:03back into the southeast on Friday night,
16:05because by Friday we may see some slightly less hot air coming in from the west.
16:10But still a potential Friday night into Saturday of temperatures,
16:13particularly in that southeast corner,
16:14high probability of them staying over 20 degrees Celsius.
16:18I might be overplaying it a little bit, but just giving you the idea
16:21that we are going to keep this heat, particularly by night,
16:26but also by day, across especially the south over the next few days.
16:31But parts of the north are also seeing some warmth,
16:34some warmer conditions over the next few days.
16:37Tuesday's temperatures.
16:38Wednesday a little bit lower, perhaps, across Scotland,
16:40because there will be a bit more cloud here.
16:42But we are seeing the warmth building again.
16:44A bit of uncertainty about Thursday.
16:46But again, temperatures, particularly in southern Scotland,
16:48could be pushing up in and around that 30 degree mark.
16:52So that's something we need to watch as well,
16:54is that heat could push into parts of southern Scotland.
16:56But overall, the hottest weather is focused across the south.
17:00That's why we've got the amber and the red warnings in place.
17:03People have been asking about,
17:04oh, well, I'm going to get, I'm forecast to get 38 degrees.
17:07Why aren't I in the red?
17:08And as I say, because it's a combination.
17:10We issue the warnings because they're based on impacts.
17:14What impacts we're likely to see.
17:15And there's an increased chance of impacts because of the length of the hot spell.
17:18So it's not just one day where we get to 38.
17:21It's a combination of the length of time that we're staying in this very hot air,
17:26the humidity, and those nighttime temperatures as well,
17:29likely to stay up.
17:31Because then you can't, if you don't get enough sleep,
17:33then your body can't recover.
17:34And then it struggles again through the day
17:36to cope with the kind of temperatures that we're looking at.
17:39So some very high temperatures on the way.
17:41That high humidity also likely to be playing a key part
17:45in what we're likely to see over the next few days.
17:48Just one more map I wanted to show you here.
17:51This is the heat index, the Humidex,
17:54which is a combination of the temperature and that wet bulb temperature.
17:59Sorry, not the wet bulb, the dew point temperature.
18:01And this is showing where that peak is in this zone.
18:05The Humidex of up to 35 degrees in this zone.
18:09That's really quite high.
18:10So it's a combination, not just the temperature,
18:12but the dew point and where we're likely to see the biggest stress on the body.
18:16It's in that zone on Thursday across southeast Wales,
18:19into the Midlands and in southern parts.
18:21That's where the humidity will be at its peak.
18:23And you can see that that area extending up of 30 plus
18:26goes and that kind of matches that amber warning that we've got in place
18:31across the UK for Wednesday and Thursday.
18:36So amber warning in place, red warning within that.
18:40Question marks about Friday, about when we're going to see the end to the heat.
18:44Will it be Friday?
18:45Will it be into the weekend?
18:46And how quickly will temperatures drop off?
18:49Are we going to see some more thunderstorms?
18:51Well, if we look at the outlook for Friday,
18:55you can see we are starting to see more showers appear on the chart.
18:59And that's basically because we're seeing that change in the jet stream.
19:03The trough is edging its way in initially.
19:05So this is the first trough, which is digging down,
19:09allowing the warm air to push up.
19:11But if we fast forward that, how that looks,
19:14what actually then happens, you get this secondary push from the jet stream,
19:19which actually then tries to push an area of low pressure and a cold front in.
19:23And that looks like eventually winning out
19:25and pushing everything away by the time we get to Sunday.
19:30But even on Sunday, you know, the hot air isn't that far away.
19:33It's only been slowly eking its way away.
19:36OK, we're not going to see the extreme temperatures.
19:38Unlikely to see those continue beyond Friday.
19:41But even into Saturday and Sunday,
19:43it still likes to be very warm across these eastern areas.
19:45And then the fresher air trying to come in as we go through next week
19:49and probably winning out.
19:50And it looks like we will see a more mobile pattern as we go through next week.
19:57There'll still be some fine weather around.
19:59High pressure is not far across the south.
20:01But we will see those weather fronts introducing cooler and fresher conditions.
20:05But when we see the transition, as is often the case,
20:08we may well see some thunderstorms.
20:10So that's the big question about when we're going to see the downpours coming in.
20:15You can see this little, I'll take the temperatures off that,
20:17little ripple, little curl in the jet stream there.
20:20That could enhance some thundery showers as we head into the latter part of Thursday.
20:27So generally speaking, it's dry and sunny for the next few days.
20:31But notice there's some mist and low cloud in the North Sea that may come onto shore at times.
20:35So that could impact the temperatures in the east.
20:38Then look at that.
20:39The potential for some thundery showers coming up late on Thursday across the southwest.
20:44So we could again see some thunderstorms.
20:46Unlikely to see any or many on Wednesday.
20:49But it's really on Thursday when we've got that combination of the jet stream rippling around
20:53and destabilizing things higher in the sky.
20:57We could see some heavy showers coming up from the southwest.
21:00Don't take these charts.
21:01Literally, as I say, there's a lot to play for in terms of the detail.
21:05But then we see those showers moving eastwards.
21:08And generally then the weather turning more showery as those weather fronts try and push in
21:13and introduce that fresher air as we go through the weekend.
21:15So we are likely to see a change, but it's going to be a gradual change.
21:20Where we see things changing most dramatically,
21:23that means we could well see some further thunderstorms and some big downpours and some lightning.
21:28So we'll need to keep an eye on those as they develop
21:30because of all the heat we've got at the moment.
21:32That provides extra energy for the atmosphere.
21:35But certainly in the outlook we could see some changes coming in.
21:39We will see some changes coming in.
21:41But it's still likely to be very hot across eastern areas on Friday
21:45and even into the start of the weekend.
21:47As we said, it could be a very, very warm night again on Friday night and into Saturday morning.
21:55Got to get those right.
21:58So the temperature's there again.
22:00If we just move forward a day, you can see that those temperatures start to drop off again.
22:04Saturday, probably closer to 30 Celsius across the east.
22:07A lot will depend on the sunshine, but back for many in the west, certainly more to more typical conditions.
22:13And then perhaps cooler still on Sunday.
22:16It's still quite warm, probably still quite humid.
22:17And it's not that clear cut, but that is the general trend.
22:21We will see those temperatures coming back down, but we will also potentially, with that change,
22:26see some thundery showers, particularly during the course of the weekend.
22:31So we won't go into much more detail about what's happening next week.
22:33I think I'll save that for the 10-day trend for tomorrow.
22:38So, yes, temperatures are on the way down, and it's to do with the bigger picture,
22:43and we're all to see more of an Atlantic influence as we go into next week.
22:48Right.
22:48Lots of really good advice about how to stay cool in this hot spell on the Met Office website.
22:54And urge people not to cool off by jumping in water as well.
22:58That's a really important message.
22:59Lots of people in this heat want to go and cool off.
23:04But the messages from our friends at the RNLI and the RLSS, please don't do that.
23:11If you are going to the beach, go to a lifeguarded beach.
23:14And if you are going in any other body of water, make sure it is supervised.
23:18If you do get into trouble in the water, then float to live.
23:22Lie on your back and try and float, try and calm yourself down,
23:26because cold water shock is a very real thing.
23:29And if you just jump into these bodies of water where they are cold,
23:33it will be refreshing, but it is going to potentially cause that cold water shock,
23:38which is very real and very dangerous.
23:40Again, lots more advice about that on the Met Office website.
23:43Thank you very much for watching.
23:45Please do try and stay cool.
23:47Keep up to date with the weather warnings.
23:50Keep up to date.
23:51See if you're going to be impacted.
23:53Temperatures are varying quite a bit over the next few days.
23:55It's not all about the heat.
23:57So, yeah, and do keep an eye on the radar as well.
24:00If you see any other thunderstorms on the horizon, let us know.
24:04And, yeah, keep your questions coming in the comments.
24:08We do read them, and we'll try and answer some of them in this week's live, no doubt.
24:12But that's this week's Deep Dive.