Deep Dive 27/08/2024 – Storms seasons and more
This is an in-depth Met Office UK Weather forecast for the next week and beyond. Today we look back at the recent storm season and discuss why there were so many named storms and talk about the more settled weather to come as we head into meteorological autumn. Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
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00:00Hello and welcome to the Met Office Deep Dive, our regular in-depth look at all matters
00:05meteorological. These are exclusive to the Met Office YouTube channel, so if you enjoy watching
00:11them and you want to encourage us to do more of this sort of thing in the future, don't forget to
00:16hit subscribe and that way you'll never miss an update. There's an awful lot to cover this week.
00:22Meteorological summer is coming to an end. Meteorological autumn is about to begin,
00:27although we've had a flavour of autumn during the last week or so. Last week storm Lillian was
00:33named, making it the most number of named storms in a season since the Met Office started naming
00:40storms back in 2015. I'm going to be talking to Will Lang, Met Office expert, in a bit to find
00:46out why last year was so stormy and if we can expect more of the same this autumn. But first
00:55of all, it's all about high pressure over the next few days rather than low pressure, although I
01:01thought I'd start with this graphic which sums up the rest of meteorological summer very nicely.
01:07And it shows effectively more of what we've seen during the last few weeks, and that is
01:13much more rainfall towards the northwest. Western Scotland, Cumbria, West Wales, Northern Ireland,
01:18and much less rainfall towards the southeast. And this is the amount of rain we're expecting
01:23until summer comes to an end, until midnight on Saturday. And some parts of the east and southeast
01:31not expecting any rain at all. Some parts of the northwest seeing more than 50 millimetres or so
01:36in that period, but much of that actually coming during the rest of Tuesday and into Wednesday,
01:42whilst the east and southeast experience a one day wonder, short-lived waft of warm air from
01:49the continent. And the reason behind all of that is this setup. Looking at the bigger picture,
01:55and we've seen a recurring pattern since around the middle of July. I talked about this
01:59in last week's deep dive, so check that out if you want to find out more if you missed it.
02:03But essentially, we've got low pressure between Iceland and Scotland, and we've got the jet
02:10stream coming in from the southwest, directing weather fronts and weather systems into northwest
02:15and parts of the UK. Hence the unsettled, the wet weather here, whilst further south and east,
02:21we're closer to an area of high pressure. And in fact, as the jet stream over the next 24 hours
02:26also digs a little bit further south to the west of the UK, we're going to draw up this warmth
02:34across many southeastern parts of the UK, whilst northwestern areas are cooler behind this weather
02:41front and more unsettled. So let's take a look at temperatures first of all. And I'm afraid it is
02:47once again all about the east and the southeast. Not necessarily just the southeast, of course.
02:54As far north as the Vale of York, we'll get some particularly notable temperatures on Wednesday.
03:01It's shown up there 25 in whole, but some parts of the Vale of York, perhaps up to 27, 28 Celsius
03:08or so. Somewhere in eastern England, likely to see 29 Celsius, small chance of 30 Celsius on Wednesday.
03:16There'll be some cloud around. It's not going to be entirely sunny. The sun's not as strong as it is
03:21in the middle of summer, of course. So that will mean that temperatures won't be quite as high as
03:25we'd normally expect earlier in the summer in this kind of scenario. Further west, as you can see,
03:32temperatures nowhere near as high. Scotland, Northern Ireland, western parts of England and Wales,
03:37mid to high teens, perhaps low 20s. And how does that compare with average? This is tomorrow's
03:43temperatures. As you can see, three to six degrees above average for parts of the Midlands into
03:49eastern England. Whilst there are some blue spots, if you squint at western Scotland and northern
03:56Ireland, that would suggest three to six degrees below average. And the reason behind that is the
04:03wet weather we're expecting. Now, it's already a wet day across parts of Cumbria into Lancashire
04:10into west Wales, the far southwest of Cornwall. That's the cold front that basically divides the
04:18cooler northwest with the increasingly warm southeast. But fast forwarding this to Wednesday
04:25afternoon and you can see showery rain across western England and Wales. Still some drier
04:31interludes, of course. Scotland and Northern Ireland, heavier showers and some more prolonged
04:35rain turning up across western Scotland through the day. Let's put the cloud on. And as you can
04:40see, hazy sunshine there across the Midlands, east Anglia and the southeast. So not entirely blue
04:44skies, but very warm nevertheless. Elsewhere, thicker cloud, a lot of rain, especially across
04:51western Scotland. Story of the second half of summer. That's been the story of the second half
04:56of summer. The most unsettled weather hitting western Scotland and northern Ireland, less
05:01unsettled towards the south and the southeast. This northwest-southeast contrast even more enhanced
05:09than normal. But that is about to change. If I just fast forward that, what you can see, there's
05:16the cold front, by the way. It fizzles out as it pushes east across the UK. And really, it's on
05:21Wednesday night that moves east. And while we won't see much rain from it across central and
05:27southeastern parts of the country, it will usher in those cooler airflow from the west, back to
05:35an Atlantic flavour rather than a continental flavour. And actually, Thursday, yeah, it's cooler,
05:40but you know what? Many places experiencing warm, sunny spells. And some showers for Scotland,
05:48northern Ireland, northern England, but even here, some interludes, drier compared with Tuesday and
05:53Wednesday. Even drier again into Friday. Look at that. Skip forward to Friday afternoon. A very
06:01nice day indeed across the UK. Virtually everyone's dry. It's not going to be entirely sunny. There is
06:06some cloud round, but it's drier compared with the next 24, 36 hours or so. The reason behind that
06:14is this high pressure building in. Rewinding a few steps back and I'll show you where it came from.
06:22It's coming from the Azores. Here's the Azores. Lovely group of islands. If you ever like to
06:26visit, you can get there from Portugal. But they've got a semi-permanent high pressure
06:31nearby that sometimes extends towards the UK. We call it the Azores High. That is likely to
06:37extend towards the UK during Thursday and then become centred over the UK into Friday,
06:44with the jet stream being directed to the north of the country. Although unlike Wednesday,
06:51put the temperatures on, we haven't got a feed of hot air from the continent. So temperatures
06:57will be rising as a result of a bit more sunshine around. Not entirely sunny either, but a bit more
07:02sunshine, more settled, lighter winds. But we're not tapping into the hot air of the continent at
07:08this stage. At this stage, as to be said. Now, moving that forward, and what you can see is a
07:16trend through Saturday for that high to push east and become centred over Scandinavia. There is
07:24another high that's building once again to the southwest of the UK. But as that high moves into
07:30Scandinavia, it is likely to allow temperatures to rise as the winds come in from the continent
07:37once again. You can see the warmer colours appearing there across the south once more.
07:43But Saturday into the start of Sunday, essentially a mostly fine day. One caveat
07:52is that, I'm not sure how well this will show up on the jet stream graphic, but you can see
07:57this very amplified jet stream, well to the north of the UK there. But there's this other branch of
08:02the jet stream which is over the continent. You can just about make it out there over northern Spain,
08:08some of these arrows down here. And there's basically a circulation in the upper atmosphere
08:13at the height of the jet stream, known as a vortex way up there, cut-off vortex basically, and a low
08:21pressure system way up in the jet stream height of the atmosphere over France. Now this is where
08:28there are some uncertainties for the second half of the weekend. So for the first day of September
08:32we've got high pressure close to the UK, so most places fine with sunny spells. But there are two
08:38things that could start to happen, could start to approach the UK. First there's frontal zone to the
08:45northwest that could approach and bring some cloud and some showery rain into the far northwest of
08:50the UK. Meanwhile we've got this upper vortex, this upper area of low pressure over the continent
08:56to the south of the UK, and that could start to nudge northwards to bring some humid and potentially
09:05thundery weather in from the south. A lot of uncertainty about this because different
09:08commuter models are saying different things at the moment. It's still of course five days away,
09:13but yeah if that happened then it could bring some showers into the south during the second
09:19half of the weekend as we start September. Even some thunderstorms make it feel a bit more humid.
09:24So those are the two things to watch, whether more changeable weather will move in from the Atlantic
09:28to affect northwestern areas, or whether this vortex to the south will just nudge some thundery
09:34rain in to the south during Sunday. And that and the associated uncertainties really continue into
09:43the start of next week. Now this is the graph for temperatures and for rainfall
09:51for southern parts of the UK, just to highlight the uncertainties really. And what this shows,
09:57the red boxes on the top of here are the likely temperatures compared with the average line,
10:04which is the red line, for the next two weeks. And what it's showing is that on Sunday and into
10:11Monday and Tuesday, the boxes get bigger. That indicates more uncertainty, a greater range of
10:16likely temperatures. But also the boxes are generally above the red line, so warmer than
10:20average as we potentially import that warmth and humidity from the continent. Likewise,
10:26overnight temperatures warmer than average. That's the blue line and the blue boxes. On the top,
10:31that's the rainfall. And this is from running the computer model 52 times or so. This is the
10:37European model. And what we're seeing is very little rainfall really for the rest of summer.
10:42We've already covered that. Then some of these spikes, what you're not seeing is a clear box
10:48above the zero line, but you're seeing some spikes, quite high spikes there for the middle
10:53of next week. And what that indicates is that many computer models have no rain, but some computer
10:58models have a lot of rain. And when that happens, when that's showing up, it's indicating that the
11:04rainfall would be convective. It would be showery, so hit and miss, thunderstorms potentially.
11:11That's for next week and in the south of the UK. I'm just showing the south of the UK there because
11:16it's the most uncertain aspect of the forecast. The rest of the UK likely to keep higher pressure
11:24and be mostly fine. And the reason for that is because we're moving into a weather pattern for
11:31the first week of September that is coloured in this shade of red. Now this shows the colouring
11:38of different weather patterns and their relative likelihood going out to the next two weeks.
11:44The first week of September or the first 10 days of September is shown here
11:48and it's dominated by this red colour. Red is normally associated with higher pressure closer
11:54to the UK. It doesn't always mean dry and settled because it depends where that high pressure is.
12:00And this shade of red would normally indicate higher pressure just to the north of the UK or
12:06the northwest or perhaps the northeast. So higher pressure, yes, but towards the north. That would
12:11mean lower pressure perhaps to the south, maybe over France, but maybe over southern parts of the
12:17UK for the first few days of September. Let's put a bit more detail on that. Does that work? There
12:24we go. This is the same thing but in map form and this is showing the most likely pressure anomaly
12:30for the UK and Europe here, there's Iceland, for the first week of September. And it is showing
12:36those deep red colours to the northwest of the UK, blue over the continent. So lower the normal
12:42pressure over the continent and then higher the normal pressure to the northwest of the UK.
12:48And as I say, that would indicate many places settled but always that chance for the first
12:54few days of September, a lot of uncertainty, always that chance of some thundery rain perhaps
12:58coming up from the south, a thundery low coming in from France, for example. What does that look like?
13:06Well, something a bit like this. This is the most likely weather pattern for Monday,
13:10the 2nd of September. This is showing two areas of high pressure actually near the UK.
13:16One is to the west and one is over Scandinavia. And in between we've got low pressure over Iceland
13:22but also low pressure just there over France and Belgium and the Netherlands. And these blue
13:28colours here just indicating that showery rain coming in from the continent. And also a front
13:36dangling from that low pressure to bring some showery rain into western Scotland. So those are
13:42the two areas to watch, as I say, Sunday to Monday, perhaps Tuesday as well. We're in between areas of
13:47high pressure and there's the potential for some changeable stuff into the far north and northwest,
13:52also the potential for some thundery showers into the south of the country. So it's not all
13:56plain sailing even if we do have higher pressure building through the weekend. Then this is most
14:02likely weather pattern for Wednesday, the 4th of September. It shows higher pressure again to the
14:09west of the UK but that low pressure to the south and the low pressure of Iceland have tended to move
14:14away. And what we're likely to see, this is what the general suggestion is in the model output,
14:20is this high pressure building to the west and northwest of the UK and allowing a cooler airflow
14:27but a lot of fine weather actually across the country. So perhaps our air coming from the west
14:32or northwest, areas of cloud and so on, but many places settled. So yeah, first week of September,
14:39high pressure moves in, a lot of places will be fine, increasingly warm through the weekend,
14:44especially in the south, but just those question marks over whether we get some thundery rain into
14:50southern parts through Sunday, Monday, and whether we get some changeable stuff into the northwest
14:56throughout that period. But otherwise, a much quieter start to autumn compared with how autumn
15:04last year ended up. But it's worth remembering that last autumn started off similar to this.
15:10The high pressure was in a different place but we had high pressure in charge during the first 10,
15:1411 days or so last autumn and we had as a result the warmest September on record in the UK. But
15:21then of course it completely switched around through October, November and December. What did
15:27we end up with? We ended up with the most number of name storms that we've named ever since we
15:36started naming storms in 2015. And that's why I've asked Will Lang to come back and talk about the
15:44reasons behind the number of name storms that we saw last autumn and winter and whether we can get
15:52or expect a repeat through this autumn. So, Will Lang, welcome back to the Met Office Deep Dive.
16:00You are of course a friend of the show, you've been on a few times and you're also head of
16:04warnings here at the Met Office. Plenty of warnings over the last year to keep you busy,
16:10certainly associated with storms. Anyway, it's been a particularly stormy year and the most
16:16number of name storms we've seen since we started naming storms back in 2015. That's right, we got
16:21to 12 finishing up with Storm Lillian only just last week, so that's the most we've ever had.
16:28So it has been a particularly busy year. Yeah, and some of these will really stand out for,
16:32I don't know how many of these storms stand out for viewers at home, but some of them certainly
16:37stand out for me and of course for you. Which ones in particular were most notable for you?
16:45Well, the really big ones from my perspective were Storm Babette. Lots of people will remember
16:50that from last October. Really interesting setup, really messy weather picture. You can see
16:56that we've got lots of areas of low pressure. Actually, more than one weather system was
17:00involved in Storm Babette. We had other systems running into the back of it, lots and lots of
17:04fronts. The whole point was though that these weather systems were getting stuck across the UK.
17:10You can see a big area blocking high pressure across Scandinavia. The storms were trying to
17:15move north-eastwards, trying to clear into the North Sea as they normally do, but they couldn't.
17:20So they were just getting stuck and we get these strong easterly winds feeding rain into areas that
17:24aren't really used to that heavy rain. So the interesting thing is that storms usually are
17:30named because of wind, but also rain can be involved as well and we factor that into our
17:34decision making. Yeah, and the rain was just incredible for Storm Babette. Here on the left
17:40we've got the total rainfall amount over just three days, 18th to the 21st of October. So this
17:45is the rainfall amount. Parts of eastern Scotland more than 200 millimetres in those few days,
17:50but also more than 100 millimetres across parts of northern and eastern England. And then over on
17:55this side we've got how that rainfall amount compared with the seasonal average because that's
18:01in some ways more important because it shows how exceptional this rainfall was. Huge amounts of
18:06rain and let's also consider where the rain normally falls as well. So what you'd normally
18:10look for for a season, most of the rain would be in the west. That's where the systems come from.
18:15Most of the heaviest rain would be western Scotland, parts of north-west England. But
18:20because we had these few days of weather systems coming in, driving the rain in from the east onto
18:25the hills in particular, you get this huge build-up of rain eastern Scotland, parts of eastern Pennines
18:31down into east Anglia. So that's really unusual for that time of year and that's why it had all
18:35of the impacts that it did in terms of flooding. Yeah, river that runs through Brechin of course
18:42flooded. Lots of the Trent rivers down into the Midlands, east Anglia as well flooding.
18:48Really exceptional rainfall, really important and significant impacts as well. Red and amber
18:55warnings issued across many parts of the UK. Storm Ciarán, that must stand out.
19:02Really interesting one. In some respects this had some similarities with the great storm of 1987.
19:10It didn't have that effect on the UK and that was pretty close shave. So we had a rapidly
19:14developing system moving in from the Atlantic, really deep, really tightly packed isobars.
19:20Particularly on the southern flank, that's where the strongest winds are. So if this
19:24had been shifted a little bit further north, 50 miles, 100 miles further north, we'd have had some
19:29really, really serious damage across southern England, perhaps parts of south Wales. Luckily for us
19:35it passed further south. Unluckily though for other areas, the Channel Islands, northern France,
19:40where they saw some really horrendously strong winds and some serious damage. Yeah, we were lucky
19:45weren't we? Narrowly missed similar impacts to the great storm. But it just shows here from the
19:52shipping forecast, this is the Plymouth Sea area, and it talks about violent storm 11, perhaps
19:56hurricane force 12 later. You don't see that very often in the shipping forecast. No, no, really,
20:02really exceptional winds that just went through the Channel. Still, these are the wind gusts,
20:07by the way, might be difficult to see on the screen, I understand for the audience, but we've
20:12got 66 knot wind gusts across some southern English Channel coast. But through the Channel there,
20:18that's where the strongest wave of winds hit. Northern France, wind gusts in excess of 100 knots,
20:25115 miles an hour for one or two spots across northern France. And the Channel Islands were
20:31really impacted by those winds, weren't they? So yes, as I said, if it had been further north,
20:37if we'd had those winds across southern England, then that would have been really, really nasty.
20:42So we got lucky, our colleagues in the Channel Islands and northern France not so lucky.
20:47Now, also, Channel Islands hit by a tornado in the midst of the most powerful winds going through as well.
20:55Then, moving on to January, and this substantial storm moved across northern parts of the UK.
21:02This was Storm Esher. Almost your more traditional big winter storm. A strong jet stream, a strong
21:09storm track across the Atlantic, driving systems across into the northern part of the UK.
21:16Normally, when we start to see the strength of the jet stream exceed 200 miles an hour and it's
21:22pointing towards the UK, that sets the alarm bells off and it tends to spew out these really
21:27intense storms, usually across the northern half of the country. And that's what Storm Esher was
21:32in this case. We had a red warning out for parts of northeast Scotland for Storm Esher.
21:36Yeah, and that jet stream that you mentioned, the power behind that was due to this temperature
21:44contrast across North America. So this is North America, there's Florida, you've got the Great
21:48Lakes up here. And this is just showing the temperature numbers, might be difficult to see
21:52on the screen, but we're essentially looking at temperatures below minus 30 Celsius across
21:58northern parts of the USA, and then more like mid-teens further south, and a really significant
22:05temperature contrast. And it's that contrast, even elsewhere in the world, almost halfway around the
22:09world, can have big influences on the UK. The temperature contrast here drives the strength of
22:14the jet stream out in the Atlantic, and then that becomes a real breeding ground for these storms
22:19that spit out across the UK. So that's something we always keep an eye out for.
22:24Yeah, sometimes people ask whether we're going to experience the weather that North America
22:29is experiencing, perhaps in a few days' time. And often there is a connection, but it might not
22:34necessarily be in the same way that you might expect. That's right, it's a connection. The patterns are
22:39connected, and we can spot patterns that emerge to the west of us in particular, and that might
22:45influence what we have in the UK in a few days' time. Yeah, and these were the wind gusts that we saw
22:52from Esher, and yeah, very strong winds across the UK, with wind gusts into the
22:58noughts, by the way, into the 50s there, across southern areas, but into the 70s there for
23:05northern parts of the UK and significantly higher. Yeah, it was a really, really big storm. So it was
23:09windy everywhere across the UK. Everywhere probably saw some impact in terms of trees down, etc.
23:14The strongest winds of all were for that part of northeast Scotland where they saw the most damage.
23:19Yeah. Now, last week was the week that we got the 12th named storm of the season,
23:27which meant that it was officially the most named storm since 2015 when we started naming these
23:33storms relatively small. Sample size, of course, but it goes to show how stormy it's been. But it
23:38was a different kind of storm once again, wasn't it, last week? Yeah, we see fewer storms overall
23:43in summer, but it doesn't need it to be as windy because we are more vulnerable to an extent in
23:48summer. We've got a lot of people out of doors on holidays, camping, other leisure activities going
23:55on. We have other factors as well. A lot of the trees are in full leaf, so if they come down or
23:59branches come down from those, then that can cause some serious damage. So it's another set of factors
24:03to consider, which means that it doesn't take as much to have a storm in summer as it does in the
24:08winter in terms of wind speeds alone. But that doesn't mean that they won't be impactful as we
24:12saw last week. And this is just a snapshot from the BBC website. It's showing a tent in the air
24:19there being flown up from Leeds Festival. Stages that were damaged and out of action at Leeds
24:26Festival as well. So, yeah, this is the significant thing. Storms are named based on impacts rather
24:33than wind speed thresholds, which is the sensible thing to do, isn't it? Because naming storms and
24:38our warnings are based on impacts, of course. Naming storms is all about making sure people
24:42are prepared for those impacts. Absolutely, it's about getting the message across in however way
24:47we can. And getting a warning out is something, but also giving it a name gives an extra boost
24:52to the communications. People see it on social media. If you're going to a festival, you might
24:56think, well, I need to be prepared for that. And that was exactly what we were thinking in the
25:01second half of last week when we started to see this storm emerging in the Atlantic. We were
25:08thinking, what's going on across northern England where this storm is likely to hit on Friday? And
25:13we knew things like the Leeds Festival, other festivals going on, and we take that into
25:18consideration. And that was a big part of our decision to name that storm, just to get that
25:22message across and hopefully get people to take some action and keep them safe. Yeah, that's the
25:27point, isn't it? Making these storms famous so that more people are aware that it's happening,
25:31so that they can be prepared when doing outdoor activities or travelling and so on. The next
25:37question is, why was autumn and winter so stormy? I guess there are a few different reasons, but
25:45let's bring up this graphic. And it takes a bit of explaining, but basically, here's the UK,
25:51there's Greenland, there's North America. And what you're seeing is the jet stream anomaly through
25:57autumn. Where the colours are blue, the jet stream was stronger than normal. Where the colours are
26:03orangey, the jet stream was weaker than normal. And so what this graphic for autumn 2023 is showing
26:09is that the jet stream was more powerful than normal to the south of the UK and out in the
26:14Atlantic, south of the UK's latitudes. And so we had basically a south-shifted strong jet stream
26:21through autumn. That's right. And so this south-shifted jet, remember, we talked about Storm
26:26Babette, about something coming up from the south, from the southwest. And actually, the fact that
26:30the jet is further south means that there's more of an incidence of high pressure to the north of
26:35the UK, so that blocking high-pressure signal. So that's exactly how we ended up with this
26:40situation from Storm Babette, where systems were coming up and then getting stuck and giving us
26:44lots of rain. Storm Ciarán as well, on that south-shifted jet stream, that's why it ran through the
26:50channel. Similar storms to that would more likely, in a typical autumn and winter, go to the north of
26:56the UK. And it was a bit more mixed for the winter as well, wasn't it? It was, yeah.
27:01So this is the pressure anomaly for autumn, and it goes to show much lower than normal pressure
27:06there. The blue centred over much of the UK, but especially central and southern areas.
27:12And yeah, you mentioned the winter. This is the jet stream anomaly for the winter, and it's similar,
27:19but it's a bit further north. Yeah, so things broadly coming up from that direction, but also
27:23there's a bit more signal further north as well. So there was a bit more to play for in terms of
27:27possible storm tracks. That's where we saw Storm Isher coming across this way, for example, but it
27:33did contribute to that overall wet, stormy theme for the autumn and for the winter. Yeah, and they
27:41have the pressure anomaly, so lower than normal pressure again through the autumn and through the
27:46winter. Slightly different position for that anomaly further east of the UK, but very similar.
27:53So more powerful jet stream through the autumn and winter, and generally to the south of the UK,
27:59more low pressure systems, deeper low pressure systems, all of that stuff. The next question
28:04people watching this will be asking is, why did we have that set up through autumn and winter?
28:11There are so many factors, but the main factors we were considering
28:15last year, this time last year when we talked on the deep dive, things like El Nino and La Nina,
28:23so that's about ocean temperatures in the Pacific, but again knock-on effects around the globe.
28:29Last year we were in an El Nino situation, that can favour some wetter conditions in autumn and in
28:37the first part of winter in particular, so that was one of our considerations. Another one is that we
28:41had really, really high sea surface temperatures around the UK. You remember people talking about
28:46marine heat waves at the time, and that also can provide that extra energy for storm development
28:53that we saw last autumn and winter. Yes, lots of these factors coming together, leading to wetter,
29:00windier conditions, more powerful jet stream through the autumn and winter. We've got different
29:06conditions coming together potentially for this autumn, of course. We've just issued the
29:12seasonal forecast for the autumn, here it is. If you could talk us through this, what's the
29:19seasonal forecast for this autumn? So this always takes a bit of explaining, so I'm sure viewers
29:26will have seen this before, some of you at least, but let's go through it again. What we do is we
29:31break down each of these categories, temperature, precipitation and wind speed, into three categories,
29:36so that's below normal, near average and above normal, and we assign those probabilities,
29:42and the normal probability of this happening should be in each category 20%, 60%, 20%
29:49by definition. So if we see anything different from that, it indicates that the seasonal forecast
29:55is going for something shifted in a little bit of a different way. So what this is telling us for
30:00September and October and November, which is the meteorological autumn, is that there is a shift
30:06above 20%, it's gone to 40% for warm, that's actually fairly standard because that's what
30:11we're seeing through climate change. Most of the seasons that we see will be warmer than they were
30:16historically. Interesting ones, precipitation, not 20%, 35%, so that's skewed towards the wet side
30:24of things for the UK as a whole. Also the windy side of things, so again not 20% for windy but
30:3035%. So overall for the UK as a whole it's suggesting that that season has an increased
30:37probability of being wetter and windier than average. It doesn't mean it will be, it just
30:41means that the odds have shifted a bit in favour of those outcomes. Yeah and I guess it's still a
30:4955% that it's near average, it's still a 10% chance that it's dry and cold. It could still be dry,
30:55cool and calm and we're not ruling that out. This is like assessing the odds of a sports team at
31:03the beginning of a football season for example, lots of things can change but this is just the
31:07initial indications based on the models and the other drivers that we're looking at. However based
31:13on our assessment, our expert assessment of what might be going on, near average is still most
31:18likely but there is a significant shift towards the wetter and windier conditions. What are those
31:24factors that you're looking at to inform this? Are we looking at El Nino again? Well El Nino has waned
31:31really and we're in what we call a neutral state at the moment. There's not too much going on in
31:35the Pacific in terms of the contrasts of temperatures. What it looks like will be
31:41happening in the next few months is the developing La Nina situation but it's actually not being a
31:47big player in the UK weather yet. That might come later on in the winter, we'll keep a close eye on
31:53that. So there's not a big driver from what's going on in the Pacific. Sea surface temperature
31:58is a bit above normal, not so much as last year, so that's a little bit of a factor. So there's not
32:03too much to go on in terms of the large-scale driver patterns. What we do is use our models
32:08though to give broad indications of what the pressure patterns might be across the UK.
32:14And this is a pressure anomaly chart for the next three months, so this is a forecast.
32:19But what I'd suggest we do is compare that with that graphic you showed before
32:23of the seasonal average pressure and where we saw low pressure across the UK
32:29for autumn and winter last year. Now the blue is the lower pressure than expected.
32:34The take-home message is that to the north and northeast of the UK we're likely to see higher
32:39pressure. Or lower pressure. Sorry, lower pressure, higher pressure to the west of the UK out in the
32:45Atlantic. So that's a different pattern to what we were seeing at this time last year. It is
32:49shifted further north. It does suggest a fairly mobile setup with systems coming in off the
32:55Atlantic, still a fairly strong jet stream at times, but things more likely to come across
33:01the northern half of the UK rather than getting stuck across the south and east like they did last
33:07year. So a bit more like climatology with westerlies, low pressure, more towards the north?
33:14A bit more like you'd expect. In fact, a little bit more than you'd expect from a normal setup.
33:19An enhanced kind of climatology?
33:21An enhanced climatology. So it'll probably be wet in the usual places, north and west,
33:25perhaps a bit wetter than normal. Further south you go, it's less conclusive. It might be higher
33:32pressure that's dominating there. It's very much on the boundary of things. So if there's anywhere
33:37going to be drier, it's probably likely to be the southern part of the UK.
33:40Yeah, and it's this gradient, isn't it, that we're looking at? That's lower pressure to the north
33:45and east, higher pressure there, and that gradient...
33:48And it's really subtle. And you can see that this is trying to cover the whole of the three months.
33:52And this is just trying to infer this broad pattern. So there'll be lots of other things
33:56going on in an interim. There will be times when the winds are coming from this direction
34:00and the jet stream's up here, et cetera. So this is really blurring everything together
34:05to look at the season as a whole. But this seems to be the prevailing pattern.
34:08Yeah, yeah. And so this is the most likely, but it's not certainly going to be the only pattern
34:15through the next three months, nor is it necessarily guaranteed to be the overall pattern
34:20for three months. Absolutely not. Everything is still on the table. And in fact, the UK autumn
34:25and the winter is probably characterised by its variability more than anything else.
34:30Yeah. Week to week, place to place. And also, as we've seen over the last few years, of course,
34:35from year to year, we had the stormiest season since we started naming storms in 2015 last year.
34:41Yeah, before we only had two storms and they happened in the summer, didn't they?
34:44They were both in the summer, both in August. Yeah.
34:46There's no real pattern there. We're not seeing anything hugely significant because of climate
34:51change or any other long-term trends. So there's just a lot and lots of variability in how the UK
34:59autumn and winter plays out and then the number of storms that we get.
35:02Yeah. And I guess the fact that it's so variable from year to year is because we're so subject to
35:10those small changes in the position of the jet stream that we've seen in the last few years.
35:14If it's 100 miles to the south, it's very stormy. If it's 100 miles to the north, much less.
35:20And as we always say, that's due to our privileged position sticking out into the Atlantic,
35:24but also close to the European air mass. So we've talked about winds coming in from the Atlantic.
35:30As we get into winter, when the winds come from the other direction, that's where we get our cold
35:34problems. So we can be subject to all kinds of weather. Everything is still on the table for the
35:40UK over the next six months. We are definitely in a privileged position and it makes our jobs
35:44interesting as well, doesn't it? Absolutely. Keeps us on our toes.
35:47Thank you for joining us again, Will Lang. And that's all we've got for you this week
35:50on The Met Office Deep Dive. Don't forget to hit subscribe, click like, send us a comment,
35:57a question. If you've got a question for Will, I'll pass it on and see if we can get an answer.
36:01But yeah, that's it for this week. Join us again next week. Bye-bye.