This is an in-depth Met Office UK Weather forecast for the next week and beyond. After a chilly start to the month, the sunshine has returned for many this week. However, there are changes on the way from Friday with a risk of thunderstorms and low cloud. Meanwhile it’ll turn more settled in southern Europe after the devastating impacts of Storm Boris. Bringing you this deep dive is Met Office meteorologist Annie Shuttleworth.
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00:00How long will this September sunshine last? Hello and welcome to this week's
00:05deep dive. The deep dive is exclusive to YouTube so thank you very much for
00:10joining me. Welcome back if you're a regular. Don't forget to subscribe to our
00:14YouTube channel and make sure you click on for the notifications as well. Share
00:19this video with anyone you think might be interested in learning a bit more
00:21about the weather. This week we've got a lot to cover. It's a very exciting deep
00:25dive because there is so much to talk about but also because it is actually my
00:29last deep dive for a little while because I'm going away on maternity
00:33leave at the end of this week. Thank you very much to those of you who have
00:37already noticed my expanding tummy over the past few months. Thank you very much
00:41for all those messages you've sent through but I'll be going away for a
00:45year at the end of this week and we'll be back next autumn. So that does mean
00:50I've got a lot to get through today and we're going to be talking about the
00:55sunshine this week, the weather across the UK, what's coming up for this weekend
00:59and next week. But first of all I want to talk about Storm Boris which you
01:04might have seen in the news through this week. It's brought intense rainfall across
01:08parts of Europe and you can see it here on the satellite picture. It's a swirl of
01:12cloud that's lingered across parts of Europe through much of last week
01:16actually. It started off as a small area of low pressure, that was what Storm
01:20Boris initially was, off the northern part, the Italian parts of the Alps and
01:24then moved eastwards where it stalled and continued to develop into quite a
01:28big area of low pressure that brought intense rainfall all through the weekend.
01:33Now the situation is improving but because there's so much rain that has
01:37fallen there's still impacts yet to come as the rivers continue to react. So that's
01:42a satellite imagery from Storm Boris over the past seven days but
01:47this is the radar imagery so you can get a really good idea. This starts on
01:51Wednesday the 11th of September and will go all the way through until midnight
01:54last night on Monday night. You can see as the rainfall came through it's
01:58particularly parts of Czech Republic, Slovakia, Austria, parts of Poland,
02:04southeastern areas of Germany, that's where we've seen the most intense
02:08rainfall falling over particularly a three-day period from Friday to Sunday.
02:13That's when we saw the most intense rainfall. Some areas have seen close to
02:18500 millimetres of rain falling through the total event and over half of that
02:23did fall across in some areas just in 24 hours.
02:28Parts of the Czech Republic saw nearly 250 millimetres falling over just the
02:33course of Saturday. So that's where we saw the highest rainfall totals but if
02:39we look at here this is the approximate rainfall totals we've seen over the past
02:43seven days in that area. We're a bit more zoomed in here. So where we see the
02:47blues here somewhere between 300 and 350 millimetres of rain. This is the
02:52satellite-derived rainfall from the Global Precipitation Measurement. You
02:56can find that online if you google that and have a look at this data for
03:00yourself. But this is the past seven days how much rainfall has estimated to have
03:05fallen. And yes we've seen really high rainfall amounts in just some local
03:10areas of up to 500 millimetres but actually quite widely many areas have
03:14seen 200 millimetres. So for this area of the world this time of year somewhere
03:19between 50 and 100 millimetres is the average of monthly rainfall. So this
03:23amount of rain has overwhelmed the rivers caused flash flooding initially.
03:28Now the rivers are flooding the tributaries are set initially flooded
03:32but the main rivers are now seeing the effects of that's caused landslides and
03:36lasting effects. And this sort of event is generally around 1 in 20 to 1 in 100
03:43year events. So for some people a once-in-a-lifetime rainfall event but
03:46they are becoming more frequent. In fact actually across more western areas of
03:50Germany just earlier on in June we saw a similar setup bring intense rainfall and
03:55some fairly widespread flooding as well. So these are becoming more common that
04:00can be attributed to climate change around the globe, more frequent heavy
04:04rainfall events, a warmer atmosphere can hold more moisture. So these sorts of
04:10devastating impacts from intense rainfalls are likely to become more
04:14frequent in the future. But thankfully things are changing for this area of the
04:19world, parts of Europe, as high pressure is moving in. It's moving in for the rest
04:26of the week and they are going to be seeing a drier spell. Naturally and the
04:29lead-up to this, to Storm Boris across those areas, it's actually been
04:34quite dry. There were heatwave conditions across parts of Europe just a week
04:38before temperatures into the 30s. They had heatwave conditions so it's quite
04:43dry weather so the conditions beforehand didn't really have much of an effect but
04:48thankfully they're in for a bit more of a prolonged dry spell coming up so that
04:52will really help with repairing the damage that Storm Boris has brought to
04:57such a vast area of Europe. Multiple countries have been affected but as high
05:03pressure builds in to this area of Europe that does mean that the high
05:07pressure that's bringing the fine weather to the UK is on the move as we
05:12head towards the weekend. So I'm sorry to say that if you have been enjoying
05:16this September sunshine and the fine weather, things are going to be changing
05:21into the weekend but more predominantly into next week. That doesn't mean there
05:24won't be any fine weather this weekend. Some areas will continue to see warm and
05:28sunny and dry weather but it's going to become more limited as this high
05:32pressure starts to edge its way up to the north and east of the UK and we'll
05:39start to see subtle changes. Now this chart doesn't change a huge amount, it just
05:43really looks like an easterly wind is starting to develop but actually we're
05:48starting to see more unsettled weather develop across the UK and as we head
05:54towards Saturday start to see low pressure developing down to the north
05:59and western parts of Europe and that low pressure will bring a risk of
06:04intense downpours and thunderstorms to southern areas of the UK into the
06:10weekend, from Friday really, with an easterly wind dominating across
06:15elsewhere across northeastern areas so more low clouds come for the northeast
06:20and the best of any dry weather across the north and west. So that's the
06:24generally the bigger picture but as I said it's a really subtle change and
06:27actually from this chart showing you the the pressure pattern at sea level we do
06:32have the jet stream on here as well but doesn't really tell us anything major is
06:36going to happen. So to see what else is changing I'm going to show you
06:41something else and we're going to look at the temperature of the air at 500
06:45hectopascals which is about five and a half kilometers up into the atmosphere.
06:51So the temperature of the air higher up can show us how stable or unstable the
06:58air is becoming. So this chart shows us 12 o'clock midday on Thursday this
07:05coming week and you can see here's the UK and here we have some warmer air
07:11aloft we'd say and the upper air is warmer and across the UK on Thursday but
07:18to the east of the UK you can see these blues and greens and that's what we call
07:22a cold pool lying out to the east of the UK and as this high pressure is centered
07:26up to the north and east this easterly wind that has brought a fairly chilly
07:31field to the eastern areas of the UK this week and will continue to do so
07:35this easterly wind will drag in this cold pool to end the week and into the
07:41weekend and that is what is going to destabilize the air and bring a risk of
07:46thunderstorms. So by the time we get to Friday at midday just 24 hours later
07:51this cold pool in the upper air it's not at the surface so it's not gonna be
07:55getting cold at the surface this is just the upper air will be sat over the UK
08:01now it's a few days away some models show the position of this cold pool
08:04slightly further west or slightly further south so that brings a little
08:09bit of uncertainty with exactly where it's going to see the greatest risk of
08:13thunderstorms but all models are showing this cold pool moving in and the air
08:18becoming less stable. How does a cold pool moving in like this in the upper
08:23air make our air less stable? Well to look at that we're going to have to look
08:28at something that looks quite complicated initially a tethergram if
08:32you haven't seen a tethergram before prepare yourself they are fantastic
08:37tools for weather forecasters we look at them every day you can tell so much from
08:42a tethergram here is your first tethergram if you've never seen one
08:46before but they can show you what height clouds going to form what temperature
08:50fog will form and sometimes and also if there's a risk of thunderstorms or how
08:56high the clouds will be because if you didn't know already the taller the cloud
09:00and often the the deeper the cloud and the more likely it is to bring a heavy
09:06downpours and potentially thunderstorms. Okay so an introduction to the
09:11tethergram here this is essentially the temperature plotted against the height
09:16as the height in the atmosphere so and the main things to look at is this
09:21wiggly solid line and that plots the temperature of the atmosphere compared
09:26as we go up with height so it's at a slight angle so it doesn't necessarily
09:31mean it's you can't you can't sort of read it off very easily but essentially
09:37the further back the line goes the colder it goes and the further forward
09:42to the right the warmer it is. So this is the atmosphere at midday on Thursday
09:48that's when we don't have that cold pull over the UK and then this curved
09:53line shows the behavior of how a parcel of air something from the surface would
09:58behave in the atmosphere. Now if the atmosphere is unstable a parcel of air
10:03would rise as it warms up in the daytime and then if the air was unstable it
10:09would continue to rise and that's because it would be warmer than the
10:13atmosphere but in this situation because we have that warmer air higher
10:18up it means that the parcel of air this curved line is cold as it as we go up is
10:23actually colder than the atmosphere so it wouldn't actually continue to rise
10:26and we wouldn't get big clouds forming so that means that on Thursday still
10:30looking quite sunny for most areas particularly when it's regarding
10:35convective clouds so that's your cumulus clouds, your cumulonimbus those sorts of
10:40clouds. Okay so if you're still with me now we go to the change of what happens
10:46when this cold air starts to move in higher up so how does our tethergram
10:51change when that happens? Well this is at the same time this is 12 o'clock
10:57midday on Friday when we've seen that transition of the air becoming colder
11:01higher up so you see this red and shaded area marked on I'll talk about that in a
11:06minute first thing to look at is this thicker wobbly line that's the
11:10atmosphere now plotted and you can see it's further back further to the left
11:13that means it's colder that's because the air higher up has got colder. Actually at
11:18lower levels it doesn't look too different at this stage. So as we plot
11:23the same plot of a parcel of air, parcel air would always behave in the same way
11:28thermodynamically as it moves up through the atmosphere and as we plot the same
11:33line actually this time because the air aloft is colder the parcel of air is
11:38warmer so it would be so the atmosphere is unstable so that means once it starts
11:43to rise it continues to rise all the way to the height at which it then crosses
11:48back across the line and becomes cooler than the atmosphere. So all in all what
11:52I'm trying to say is that as that cold pool comes in it becomes more unstable
11:58and because we get this big depth this is the depth the potential cloud height
12:03we could see and this is deep enough to produce some cumulonimbus clouds that
12:08would bring a risk of thunderstorms from Thursday evening into Friday and that's
12:15across southern areas. I should say this is for somewhere around the west
12:19Midlands, southwest Midlands that's where we're going to see the greatest risk I
12:23think of this where as this cold pool starts to move in and starts to move in
12:29for Friday and then it hangs around for the weekend in fact. So how does that
12:36look on the maps? Well we have got I'll just play through so this is Thursday
12:46we get the cloud on as well we've got this easterly wind so all the way
12:49through Wednesday and Thursday we've got that high pressure easterly winds
12:53bringing in low cloud overnight. We start to see those easterly winds and bring in
13:00the cloud that will linger a bit longer through Thursday and potentially into
13:04Friday as well. But Thursday night we start to see some of this unstable air
13:09moving in from the near continent you can see these wispy clouds these are
13:13starting to see some rain develop so there's potential we could see something
13:16from Thursday evening but most likely it's actually from Friday once the
13:20sunshine gets to work and you can see intense rainfall very bright colors
13:25developing on the on the charts here. Let me just go back to Friday so that low
13:37cloud to start the day and then quite quickly as soon as the sun comes out
13:41intense rainfall developing through a large swathe of southern and central
13:45parts of England and parts of South Wales as well. Now the nature of
13:48thunderstorms means that you can't take this exactly for word and it's not
13:55necessarily going to happen exactly like that but gives us a good idea of the
13:59threat of thunderstorms and then we'll continue through the weekend as a low
14:02pressure dominates to the south we then start to see the surface level starting
14:06to change that low pressure at the surface and continuing to drag up a risk
14:11of potentially unsettled weather from Europe through Saturday and Sunday so it
14:16will turn increasingly unsettled across southern areas. Meanwhile across the
14:21east we've still got this easterly wind low cloud drizzly rains is probably
14:26going to be quite a cool and dull weekend for many eastern areas or
14:30northern parts of the UK particularly across parts of eastern Scotland
14:35northeastern England and meanwhile as again a third zone across the north and
14:41west Northern Ireland and Scotland seeing the best of any dry weather let's
14:46go back to Friday and best of any dry weather staying dry here so we look at
14:53the rainfall totals that gives us a good idea let's look at the 24-hour rainfall
14:57totals from Friday that's to midday Friday midday oh that's gone back to
15:06three hour there we go and midday Saturday so a risk of some quite intense
15:11downpours we could see 50 millimetres falling in a few places in quite a short
15:15space of time so it's got the potential to bring some disruption so that's worth
15:19keeping up to date we'll be keeping a close eye on that as we get closer to
15:23the weekend Friday and the weekend as to whether we've got a risk of
15:27thunderstorms developing across the south and across the northeast we'll
15:32just start to see that drizzle bringing in the cooler weather and the duller
15:36weather but meanwhile staying very dry across the north and west so Western
15:42Scotland Northern Ireland the place to go for any dry and sunny weather the
15:45continued nice weather we've had this week and for the weekend if you are in
15:50the south though please stay tuned we'll have more on the 10-day trend tomorrow
15:53on that and I think it's Alex Deacon doing the 10-day trend so he'll have
15:58more on that for you tomorrow and so how long that's what we wanted to have
16:07a look how long will that situation last well what's going to happen into next
16:11week is probably an even bigger transition to that more unsettled weather
16:16this is the pressure pattern the trend and the pressure pattern from decider
16:21and this looks at lots of different models and the Met Office model the
16:26European model as well and predominantly through this and for the
16:31next two weeks and and the red colors show the high pressure the blue colors
16:35show the lower pressure we have shown this a few times so some of you may be
16:38familiar with this chart and but the high pressure through this week in
16:42general it does move away to the north and east but we get that kind of blocked
16:46pattern with low pressure just sitting to the south higher pressure dominating
16:50to the north and and then from around midweek next week Wednesday the 25th
16:56of September they're showing them as things become sort of over 50% likely and
17:01to be more blue dominated that's low pressure dominating and more of a
17:06westerly wind Atlantic mobility and that's probably what's going to
17:12dominate in fact all the way through until the weekend of the 28th of
17:16September thereafter into the first week of October we could start to see more of
17:21a 50-50 split between the high and the low pressure it's a couple of weeks away
17:25I think more likely we'll continue to see this low pressure dominating and at
17:30least well for much of next week once it does set in arrive and and probably
17:35lasting at least until early October so what does that look like and well we'll
17:41have low pressure pushing in from the south and west bringing with it this I
17:47mean it's fairly mild there it's going to be it's not going to turn
17:50particularly cold we've had our temperatures fluctuating quite a bit so
17:53far through September we had a really cold week last week temperatures are
17:58actually quite high this week above average and then into the weekend
18:02they'll probably be around average once again away from the north and east and
18:06but southwesterly winds through next week will bring low pressure wet and
18:11windy weather across north and western areas pretty typical setup for the UK
18:16dry weather across the south and east now the south and east may hold on to
18:20that dry weather through a lot of the latter part of next week if these low
18:23pressures take a while to push through but I think it's most likely to turn
18:27wetter and windier there's a chance we could see some ridges between these low
18:32pressure systems and so it's not going to be a total washout or change to
18:37complete autumn necessarily but it's less is not going to be as settled or
18:43nowhere near as dry as this week next week is looking wetter than the week
18:47we're having at the moment but the dry weather we've got at the moment is
18:53it's bringing plenty of clear skies overnight as well and I wanted to finish
18:58by showing you this lovely picture we had from Chris Jones shared this with
19:02our love UK weather hashtag on Twitter with us yesterday and tonight is in fact
19:08the full moon for September it is the harvest moon known as the harvest moon
19:15it's a full moon tonight there's also potential for to see a partial solar
19:20eclipse this evening and sorry a partial lunar eclipse this evening of
19:24the moon and before you see the full moon and there will be clear skies for
19:29many of us plenty of opportunity for stargazing and getting some great
19:33pictures like this one over the full moon I think the potential for early
19:36morning fog throughout the rest of this week as well and will bring some
19:40beautiful sunrises for some of us as well so please make sure you share any
19:44more pictures with us and as Chris has done with our hashtag love UK weather
19:49you can do that on Instagram and on Twitter or X as well but that is all I
19:56have time for for today we've covered quite a bit if you have any questions or
20:01anything I'll be around to check out the comments for the next couple of days and
20:05so I'll be checking in on all your comments and but thank you very much for
20:10watching thanks for joining us we couldn't do these without you guys
20:14watching so give us your feedback make sure you subscribe to our channel and we
20:19really appreciate all your views and comments and feedback and again as I
20:24said I won't be around for a little while so thanks for your support over
20:27the next few months and I will see you again next autumn bye bye