This is an in-depth Met Office UK Weather forecast for the next week and beyond.
The weather turns colder this week - cold enough for mountain snow in Scotland. Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
The weather turns colder this week - cold enough for mountain snow in Scotland. Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
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00:00 Hello and welcome to the Met Office Deep Dive, our regular in-depth look at the UK's weather
00:06 for the meteorologically minded.
00:09 And this week, it's going to feature a return of the zero-degree isotherm, a return of the
00:16 S-word, snow, and introducing for the first time on the Deep Dive, a histogram.
00:24 More on all of that in just a moment, but I thought I'd start with this.
00:28 This is the satellite image of the, well, North Atlantic and Europe area over the last
00:34 few days.
00:35 It runs from Saturday, the 1st of June, up until the present day.
00:39 And it's a great way of showing how the weather patterns have evolved and how they are changing
00:44 during the next few days.
00:46 And you can identify the position of the jet stream just by this satellite image.
00:51 So the jet stream is marked out by this streak of cloud, if you can see it there.
00:57 The start of June, running to the north of the UK.
01:00 That's where the jet stream was running.
01:02 But this extra push of cloud towards green, and that's a push of the jet stream north
01:06 on the other side of the Atlantic.
01:08 And then the cloud sinks south across the UK.
01:10 That's the jet stream sinking south across the UK.
01:14 So that, over the next few days, this is on a loop, by the way, so we're back to the weekend
01:19 again.
01:20 Over the next few days, that sinking line of cloud, the sinking jet stream, will introduce
01:26 more changeable and much cooler conditions across the UK.
01:30 Another thing that's quite interesting to me anyway, to point out, is this closed circulation
01:35 that we've had over the last few days, close to the Azores.
01:38 Lots of showers and thunderstorms down there.
01:40 We basically saw a cut-off area of the jet stream just form its own circulation over
01:45 the Azores.
01:46 Now, we've got the jet stream, the main branch, dipping south over the UK.
01:51 And you can see the speckled nature.
01:53 Actually, I'll zoom in a touch there.
01:55 The speckled nature of the clouds coming in at the moment behind this main area of cloud.
02:01 So over the last couple of days, these speckled clouds here making an appearance into Scotland.
02:08 And that basically, there we are, that sums it up for the rest of the week.
02:13 Basically, the jet stream sitting to the south of the UK and much cooler, more changeable,
02:19 more showery weather in general for the UK, particularly towards northwestern parts.
02:26 And that is the current shape of the jet stream.
02:27 We've got this dip and we've got this upper low pressure in the dip and this surface area
02:33 of low pressure you can see near Iceland.
02:35 And really, that's how the situation will remain during the week ahead.
02:41 So if I press play there, you'll see this cold front coming south.
02:45 That's going to contain some cloud and some rain crossing southern parts later Tuesday.
02:52 Into Wednesday, that clears through.
02:54 And then we're all in this unstable, showery, northwesterly airflow with low pressure remaining
03:01 anchored to the north of the UK.
03:03 These weather fronts coming through, occluded fronts, bringing more persistent rain at times.
03:08 But in general, it's showers coming into northwestern parts.
03:12 The jet stream to the south, allowing cooler air to affect the whole of the UK for the
03:19 next few days up to and including much of the weekend.
03:24 Here's Friday.
03:25 That low pressure is remaining more or less in the same place.
03:28 It's starting to fill, so perhaps becoming less unstable.
03:31 We've got this large area of high pressure, meanwhile, sitting to the west of the UK.
03:36 And so that's allowing the jet stream to continue to sit in the same place.
03:41 This high pressure is blocking any progression in the system and keeping things very stationary
03:49 over the next few days.
03:51 And essentially, that northwestly airflow stays with us into the weekend.
03:55 But later in the weekend, some signs that that high to the west is going to build in
04:01 from the west.
04:02 Very slowly, it has to be said.
04:04 So very slowly transitioning back to something less cold, less blustery, less showery in
04:12 the north.
04:13 But it's probably going to take all weekend and possibly the first day or two of next
04:19 week before all of us notice the influence of that high pressure.
04:26 Some areas will notice it first.
04:27 The south and southwest will be mostly settled end of this week and into the weekend.
04:33 But it's not until really the middle of next week that that high pressure exerts much more
04:39 dominant control across the whole of the UK.
04:42 Of course, with these weather fronts potentially toppling in over the top of that high.
04:47 But let's go back to the beginning because I just want to put on the temperature at 5,000
04:54 feet.
04:56 Why do we show the temperature at 5,000 feet?
04:58 It's actually a good proxy for air mass.
05:01 So where the air is coming from, how cold, how warm the air is.
05:04 If we put on the temperature at the surface, that's much more affected by day-night differences,
05:10 mountains, coast, all this stuff.
05:12 So this shows basically the character of the air, the personality of the air.
05:17 And you can see this air mass coming from the north and northwest.
05:22 We've got the blues coming back, displacing the oranges.
05:26 We've got the colder air arriving.
05:29 And it's going to be blustery.
05:30 It's going to be windy across many parts of the UK, but particularly across the north
05:35 and northwest.
05:36 And I'll be taking a look at wind chill in just a moment as well.
05:39 But effectively, we've got this air mass with us for the next few days.
05:44 The nadir of the temperature this week is actually Wednesday because gradually, as the
05:49 area of low pressure to the north fills and with the showers that develop, they help to
05:56 stir up the temperatures from the surface up to the top of the atmosphere.
06:00 So they help to mix up the air somewhat.
06:03 So when you've got a very showery airflow, it does tend to slightly warm up the air eventually.
06:09 And also, of course, the source of the air becomes increasingly cut off.
06:14 So it's not necessarily directly from the Arctic.
06:16 So gradually, the air becomes less cold.
06:19 Wednesday is the dip in temperatures, both by day and by night.
06:23 And then gradually by the weekend, things are becoming a little less cool.
06:28 But we're not looking at above average temperatures really until at least next week.
06:33 There's that high that wants to move in through the weekend, but it is going to take its time.
06:38 And really, it's only as that high pressure builds and the winds begin to ease through
06:42 the start of next week that temperatures are likely to start to climb to average or slightly
06:47 above average in places.
06:49 And let's take a look at the weather quickly, because really, it's very similar weather
06:55 over the next few days.
06:56 So I'm not going to go into tremendous detail.
06:59 Tuesday is the day where many places are seeing outbreaks of rain across the country from
07:04 north to south.
07:05 And you can see this band of rain later Tuesday.
07:07 It fragments, so it's showery on and off rain across southern and southeastern parts.
07:12 It moves into the continent, and that's the cold front.
07:14 Then we're all into this unstable northwest of the airflow, but on the cloud as well.
07:18 And what you can see are a lot of showers.
07:22 Just pause it there.
07:23 That's midday Wednesday.
07:25 Showers even across some southern and central parts.
07:28 It wouldn't rule out a shower anywhere in the UK, but the further south you are, the
07:33 less frequent, the less widespread there'll be, the greater chance of staying mostly dry
07:38 effectively with some bright spells.
07:39 It's going to be less windy in the south as well, but some patchy cumulus, stratocumulus
07:44 cloud out there.
07:45 Now, further north and northwest, you can see the showers become more frequent.
07:49 And so northern and western Scotland's certainly seeing frequent showers, perhaps some small
07:53 hail, some rumbles of thunder as well, and over the mountains, some snow.
07:58 I'm going to be looking at that separately in just a moment.
08:01 Skip forward to Thursday.
08:02 Really, it's more of the same.
08:03 Yeah, a clear start to the day.
08:05 Quite chilly start in many places, but we've got further shower development, further cloud
08:11 development as the day goes on.
08:12 So the sunniest part of the day will be in the morning.
08:14 The cloud builds again, mostly dry in the south with some bright or sunny spells, but
08:20 a cool breeze.
08:22 Further north, that gusty wind blowing in frequent showers across northern and western
08:26 Scotland in particular, parts of Northern Ireland, northern and western England, as
08:28 well as parts of North Wales.
08:31 But effectively, it's very similar to Wednesday and very similar again on Friday.
08:37 A clue to fronts will come through at times, so some more prolonged rain moving through
08:43 the northwest of the UK, perhaps from time to time, it'll move through quickly.
08:47 Effectively, it's showery over the next few days with the showers focused particularly
08:53 across the northwest of the UK, but always a chance of the odd fleeting shower further
08:58 south.
08:59 And this is how Wednesday unfolds into the weekend.
09:02 Another pulse of those north-northwesterly winds, further showers coming through across
09:06 Scotland.
09:08 A city of mostly fine weather further south, certainly not a heatwave.
09:13 Temperatures a little below average across most parts, but with lighter winds further
09:19 south with some bright or sunny spells coming through, not feeling terribly unpleasant either
09:23 of course.
09:24 The sun is quite strong at this time of year.
09:26 So that's Saturday and really Saturday's another similar day to Wednesday, Thursday,
09:33 Friday.
09:35 Showers mostly across northwestern parts of the UK.
09:40 Now let's take a look a little bit more in depth at temperatures because that's the thing
09:46 that is most interesting this week of course.
09:48 We're in the first proper week of meteorological summer, but temperatures are falling this
09:54 week because of that airflow.
09:55 The winds are coming from the northwest.
09:57 And so these are the maximum temperatures on Tuesday.
10:02 And the numbers that show up here, these are the temperatures that are likely to be experienced
10:07 in main urban areas.
10:08 So we're talking about 14, 15 in the north, 16, 17 for central areas, perhaps a 20 there
10:14 for the south and southeast, or 21.
10:17 Into Wednesday and you'll notice those temperatures have come down by a degree or two or three
10:23 degrees.
10:24 Mid-teens at best in many places, perhaps 17 there in the southeast, 12 or 13 for Scotland.
10:32 And by Friday, similar sorts of values.
10:36 So low teens up to high teens perhaps.
10:40 And Saturday once again we're talking about perhaps a slight recovery in temperatures,
10:46 but very little difference.
10:47 So how does that compare with average?
10:51 This is Wednesday's maximum temperatures compared to the - this is the June average by the way.
10:57 So it's the average that you'd normally see with the month as a whole.
11:02 And of course June tends to warm up from the start to the finish.
11:05 So you would expect slightly below average temperatures at the start of June compared
11:10 with the whole of June.
11:11 But this shows that quite widely across northwestern parts of the UK temperatures are several degrees
11:16 below the June average.
11:18 But this is Wednesday and then you'll notice slightly less cold on Thursday, not much in
11:23 it really, a degree or so.
11:25 Again some recovery on Friday and into Saturday as well.
11:28 But the greatest anomaly is across the northwest of the UK, closer to normal there across the
11:34 south and southeast.
11:37 Another way of showing temperatures - we love showing this on the deep dive - click on the
11:42 maximum temperatures is by these graphs.
11:46 So this shows the maximum temperature out to Sunday for a specific point in the graph.
11:52 At the moment it's just there to the south of Manchester.
11:55 But if I put my pen on the screen and scroll around you can see that many central parts
12:01 of England there, we've got a maximum of 13 degrees on Wednesday, some recovery there
12:05 to 14 or 15 later this week.
12:08 If I go a bit further south, again you can see the coldest day there near Southampton,
12:14 14 degrees on Wednesday, some recovery up to 17 degrees by the weekend.
12:19 Moving down towards the far southwest, this is Cornwall, 12 degrees there showing for
12:25 Wednesday 13 Celsius and some recovery.
12:29 Southeast so probably the warmest part of the country around London, 14 degrees on Wednesday,
12:35 recovery to 17 or 18 by the weekend.
12:38 And we can just draw a little line and travel north, there's the Pennines, we'd expect it
12:46 to be a bit colder there, the Grampians and yeah you can see how chilly it is but some
12:53 recovery there by Sunday.
12:56 The far north of Scotland, these are the maximum temperatures, 7 or 8 Celsius.
13:02 And for Northern Ireland as well, their coldest day quite clearly Wednesday.
13:09 And what's interesting about this is that it's showing values that are lower than those
13:15 urban areas that I mentioned earlier because those urban areas get slightly warmer and
13:23 these are where most people live, these places, but this is sampling much of the countryside
13:28 obviously.
13:29 But another way of showing the distribution of temperatures across the country is by using
13:37 one of these, a histogram.
13:41 Now this is very experimental and it might not work.
13:45 Let me know if this is just too confusing or if it could be improved or made clearer.
13:52 Literally this is two hours old, this graph, I drew it up in my lunchtime.
13:57 Just thought I'd play with something a bit different for once because this shows the
14:02 distribution of temperatures across the United Kingdom, the land areas, and it's sampling
14:09 the temperature data at 2km resolution.
14:13 So if you divide up the whole of the UK into 2km squares and then you count up how many
14:18 squares are at say 6 degrees, how many are at 12 degrees, it counts them up here.
14:24 And this is the count, this is the number of grid squares.
14:26 It's an exponential scale by the way so there's the 100 marker, there's the 10,000 marker.
14:32 So that just helps to show up some of those lower numbers.
14:36 Another thing to point out is that this is showing both the daytime maximum and the overnight
14:40 minimum temperatures.
14:41 So this, right, this is Wednesday.
14:44 So this is showing Wednesday's morning's minimum temperatures, so the temperatures people will
14:49 be waking up to on Wednesday morning.
14:51 And the minimum temperatures are coloured up in this kind of blue-grey colour.
14:56 And then the maximum temperatures, so that Wednesday afternoon's numbers basically, showing
15:01 up in the orangey colour there.
15:03 Apologies if I've got the colours wrong, I'm completely colour blind, I've no idea.
15:07 But that's how it looks to me.
15:09 Now, what this is showing is that Wednesday morning's minimum temperatures are mostly
15:16 going to be in the range of 2 to 6 degrees.
15:20 That's where these highest counts are, up to 10,000 grid squares, OK?
15:26 But there are a few grid squares, 100 or so, that are showing below freezing.
15:29 So that's what that's showing.
15:31 And you can see, this is useful to see the extremes.
15:33 So some grid squares as low as -1, -2 degrees, but not many.
15:40 Other grid squares, quite a number of them, are in the mid-single figures on Wednesday
15:44 morning.
15:45 By the way, I've also limited this to everywhere below 200 metres, so it's not sampling hills
15:51 and mountains, just to make it a bit clearer.
15:54 Also Wednesday afternoon, we've got the maximum temperatures, and what you can see there is
15:59 that there's a lot of sites that are showing 12 to 16 degrees, a few that are showing 18
16:07 degrees.
16:08 So what you can see there is that across the landmass of the UK on Wednesday, many places
16:12 are starting the day with mid-single figures, a few spots are starting the day lower than
16:17 that.
16:18 Many places are ending the afternoon with temperatures in the mid-teens, generally,
16:23 that's where a lot of these are clustered, but then there are a few more extreme spots
16:27 that are warmer than that, up to the high teens.
16:30 Now that might be where most people live, for example, the centre of London.
16:35 But this is just looking at the land area of the UK.
16:38 That's Wednesday.
16:39 If we skip forward to Thursday, and you can see there's a bit of a change there.
16:44 So this is Wednesday, this is Thursday.
16:47 There are a few more Thursday morning with these lower numbers, so a few more land areas,
16:55 so a few more grid squares that are below freezing.
16:59 But equally there are a few more in the afternoon that are warm.
17:02 So a warmer afternoon, slightly, slightly colder start to the day potentially, but there's
17:08 a greater spread, so greater variability across the UK.
17:15 Watch what happens if I change it to Friday.
17:18 And fewer of these colder values, less spread actually as we start Friday, so this is Friday
17:24 morning.
17:26 Most places are mid to high single figures, so we haven't really got a frost on Friday
17:31 morning anywhere.
17:33 And then on Friday afternoon there are more of these grid squares that are up to 16 to
17:39 18 Celsius, so you can see this warming trend, but also there's less variability and that
17:43 suggests that there's perhaps a bit more cloud cover on Friday, a slight change in wind direction,
17:48 it becomes a bit more westerly for a time, and so there's less of a contrast across the
17:53 UK and less cold air in place.
17:55 By Saturday actually that spread gets a bit bigger again, it's a colder start in some
18:00 places so more clear skies perhaps, lighter winds as well, a bit of a colder start.
18:07 But equally by the afternoon we're back into slightly higher numbers, high teens, a few
18:12 spots, 20 Celsius or so.
18:15 So I've no idea if any of that made sense, but I thought I'd experiment with it, get
18:19 your feedback and see where we go from there, if we ever want to show this again or if it's
18:24 a complete disaster.
18:26 Just let me know in the comments.
18:28 But that's effectively everything I wanted to show you for this week's Deep Dive.
18:35 And oh, I promised it didn't I, the S word, snow, and I haven't mentioned it yet so just
18:43 quickly I wanted to look at the freezing level.
18:47 We have shown this before, the height of the zero degree isotherm, and you can just about
18:53 make out the UK there, I know the border isn't particularly clear but you can see the towns
18:57 and cities.
18:58 And what this shows is the height above sea level of the zero degree isotherm.
19:03 And the top colour on the key there, above 1400 metres, means that the zero degree isotherm
19:09 is above all hills and mountains in the UK.
19:13 You're not going to get snow where it's that colour basically.
19:17 But you can see these other colours coming into the north-west on Tuesday.
19:20 And if we skip ahead to the start of Wednesday, because that's when the coldest air arrives
19:25 across northern parts of the UK, and we've got these different shades of green across
19:30 England and Wales and parts of Ireland there, some blues into Northern Ireland, the far
19:36 north of England and Scotland.
19:38 And the blues would suggest a freezing level of 600 to 800 metres.
19:43 But a general rule of thumb is that you take off 200 metres because the snow doesn't immediately
19:50 turn to rain when it goes from the zero degree isotherm into warmer air below.
19:55 There's a difference of about 200 metres, so it takes about 200 metres because of something
20:00 called evaporative cooling, and also if the precipitation is heavy, then that gap becomes
20:07 even bigger.
20:08 So typically a rule of thumb is you take 200 metres off these values and that's the height
20:13 of the snow.
20:14 So what we're looking at is about 600 metres potentially for Wednesday's showers across
20:20 Scotland, perhaps the far north of England, for some snow to be falling.
20:25 And then later Wednesday you can see the greens pushing those blues further north again.
20:30 So really that dip, that nadir in temperature, in freezing level is Wednesday morning.
20:37 That's when the greatest chance of some snow coming down to 600 metres.
20:40 By the time we get to the end of the week, the freezing level is above 1000 metres again,
20:45 so really it's the very tops of the Scottish mountains, for example, where we're likely
20:49 to see some white stuff.
20:51 But this isn't particularly unusual for June.
20:56 We've checked with our climate experts and they've suggested this happens, snow on the
21:02 Scottish mountains, every three to five years.
21:05 So it's pretty interesting to be talking about snow for the first time for a few weeks,
21:11 if not months, but nothing especially unusual about it.
21:16 And it's Wednesday morning that we're most likely to see those snow levels come down
21:20 to about 600 metres or so before gradually warming up later in the week.
21:26 And that really is it from me and I hope you've enjoyed it.
21:31 Let me know what you think, let me know if you've got any comments, any feedback, any
21:35 suggestions.
21:36 We like hearing from you.
21:38 And don't forget to hit like and subscribe if you want to see more of these things in
21:44 the future.
21:45 Thanks very much.
21:46 Bye bye.
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