This is an in-depth Met Office UK Weather forecast for the next week and beyond.
High pressure is here - and it's here to stay for some time.
Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
High pressure is here - and it's here to stay for some time.
Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
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NewsTranscript
00:00Hello and welcome to the Met Office Deep Dive. All year we've been waiting for
00:05high pressure to turn up. When it finally does it arrives in October and it's a
00:10cloudy high. How long though will high pressure stick around and will it ever
00:15give us some sunshine? I'll be trying to answer those questions in this week's
00:19Deep Dive. Thank you for joining me on YouTube or on the Met Office app and
00:23it's at this point that we normally ask you to hit subscribe. It allows us to do
00:29more videos like this Deep Dive which has been going for almost two years now.
00:33And we always read your comments, we always take on board your feedback. One
00:39request has been popping up time and time again and we've been working behind
00:45the scenes here at the Met Office to make that request a reality.
00:50Unfortunately I can't say any more right now but if you are interested in what
00:55this mysterious request is and what we've been doing to make it a reality
00:59you have to tune in to next week's Deep Dive and we'll explain more at that
01:05point. But without further ado again please do hit subscribe, send us a like,
01:10send us a comment because you never know one of your suggestions might become a
01:14reality. Now I mentioned that it's a cloudy high but it's not cloudy for
01:18everyone. Let us know in the comments if you've seen some sunshine through the
01:21day because some areas have seen. This is the satellite image at 1 p.m. Tuesday
01:2629th of October. A lot of cloud as you can see but some areas are a bit more
01:33favoured than others for sunny skies. Most notably if I just draw on some
01:38weather symbols here you can make a bit more sense of it. Some parts of eastern
01:43England, eastern Scotland seeing decent sunny spells whilst well as you can see
01:50western Scotland a lot of low clouds and hill fog, some mist and so on. Now the
01:57reason we've got better chance of sunshine through eastern Scotland,
02:01north-east England is because we've got this westerly airflow so that's leaving
02:04a lot of low cloud across western Scotland but of course it's then
02:07breaking up over the hills. Further south the cloud breaks are somewhat more
02:11random because we haven't got that same mechanism. The winds aren't coming
02:15so much from the west. We've got high pressure more or less centred over the
02:19top and so yeah there are a few cloud breaks out there but they're not
02:23particularly organised or particularly reliable. They're a bit more tenuous.
02:32They're floating here and there and that's really the theme across southern
02:35parts of the UK over the next few days because high pressure has arrived and
02:40it's here to stay. To explain how we got into this situation in the first place
02:45with high pressure in charge let's go back to the beginning. Let's go back to
02:51Thursday and in last week's deep dive I was talking about how the jet stream was
02:56expected to become increasingly amplified, increasingly wavy across the
03:00Atlantic and that we'd see a cut-off vortex form that would eventually lead
03:06to higher pressure and actually this is visible now in the satellite imagery
03:11from the last few days. We can see what happened. In fact I'm going to try and
03:15annotate what happened. This was Thursday's satellite image so clear
03:20skies across eastern parts of the UK, cloudier further west and this long
03:24string of cloud out to the west but if I draw the shape of the jet stream which
03:29you can almost trace these areas of cloud to draw it on. The jet stream came
03:35out of Newfoundland there and then came south and it's at this point that it
03:42became really elongated and then rose across Ireland there and then into
03:49Scandinavia so you can see how wavy it is and it's within this area that you
03:54can also see an emerging area of low pressure, this cloud head here and these
03:59big shower clouds also forming. Skip forward to Friday and indeed that area
04:05of low pressure did form just by here and around that low we had an upper area
04:15of low pressure so where the jet stream cuts off from the main flow and starts
04:19rotating in an almost full circle. Meanwhile the main flow of the jet
04:25stream again continued to come out of Newfoundland there but upon reaching
04:30that cut-off low, well one branch dived south, one branch went well to the north
04:35of the UK and fast forward to Saturday. Now the cut-off low basically ended up
04:46around here somewhere. The jet stream again, by the way there's a point here
04:53where ex-hurricane Oscar pushed the jet stream well to the north into the
04:59Davis Strait and that helped to amplify the jet stream but what we saw on
05:03Saturday was again two branches of the jet stream coming around like this and
05:10effectively like a stone in a stream there's your cut-off low and it splits
05:17the jet stream into two like that one branch going to the south and forming a
05:21subtropical jet stream over North Africa and then we've got the polar jet stream
05:26going to the north of the UK and higher pressure forming through the UK
05:30although this branch of the jet stream by the time we got to Sunday as you can
05:35see we've got it coming into the UK like that and there's another area coming
05:42down like that so this area of the jet stream brought some wet weather into
05:47Western Scotland and Northern Ireland through the second half of the weekend
05:53before sinking south and this is what we ended up with again a very elongated
06:00jet stream just to the south of the UK now and by Monday what that resulted in
06:06is another cut-off vortex from the main flow whilst the main flow of the jet
06:12stream is now well to the north of the UK. Now this is of interest this cut-off
06:19low over Iberia because since the start of the week we've seen some very heavy
06:25rainfall some thunderstorms and some lively showers and that circulation is
06:30going to stick around over the next few days I'm going to talk about the
06:33expected rainfall amounts in a short amount of time. Meanwhile with the main
06:38flow of the jet stream going well to the north of the UK we've got high pressure
06:42building across the country instead and here's how it looks for Tuesday
06:50afternoon. There's that low pressure over Iberia over North Africa and just to
06:57switch on the rainfall there you can see some heavy outbreaks of rain rotating
07:02around the low but the wettest weather as I'll explain in a bit more detail in
07:06a moment eastern parts of Spain. This cut-off area of low pressure also known
07:12as a cold pool because it's a cold pool of air in the upper atmosphere that
07:17drifts over warmer surface levels can lead to an enhanced temperature gradient
07:24from the warmth of the surface to the cold air way up at the height of the jet
07:28stream and of course that triggers some very lively convection or thunderstorms
07:32and that's what we're seeing. So it's an upper cold pool and what it is often
07:37known as in Spain is a Gota Fria cold pool so that's a well-known phenomenon
07:43occurring often actually at this time of year. There was a famous flooding event
07:47that brought devastating flooding to Valencia in 1957. Similar sort of
07:52phenomena with high pressure extending from the Azores towards the UK and this
07:56cut-off area of low pressure bringing a lot of wet weather and I'll talk a bit
08:00more like I say about the expected rain in Valencia in just a moment. But for the
08:05UK we've got high pressure extending now and the jet stream well to the north
08:10and just playing that forward over the next few days and you can see really
08:15there's very little change in the bigger picture. The jet stream stays to the
08:19north, diverting weather fronts. Here's a series of weather fronts that start life
08:25in the mid-atlantic and you can see a deepening area of low pressure here that
08:29is starting to move with the jet stream but because the jet stream is to the
08:34north of the UK that frontal system will also remain mostly to the north of the
08:40UK. But if I pause it there, this is Wednesday evening, what you can see
08:43there's an area of low pressure near Iceland. A little bit of uncertainty
08:47about exactly how far from Iceland it will be but we've also got on the
08:52southern flank of that low tightening isobars across central and northern
08:57Scotland. So that's going to lead to increasingly windy weather Wednesday
09:00night into the start of Thursday. The weather front meanwhile brings mild air
09:05across the UK, although it has to be said by the way that the colours here reflect
09:11the temperature at 5,000 feet. Why do we choose 5,000 feet for this? It's because
09:16it shows quite clearly areas of similar weather, air masses, that's what they're
09:21called. And so we've got this warmth, this warm air mass that originates
09:25towards the southwest of the UK extending across the UK. But at this
09:30time of year you can often have very different circumstances towards the
09:34surface of the ground rather than at 5,000 feet and it won't be nearly this
09:37mild. The reason for that is because cloud breaks at night will lead to lower
09:41temperatures where we get those cloud breaks because of the increasing length
09:45of nights and also because the relatively low cloud during the day will
09:49prevent solar insulation. So yeah, either way if we had this situation in the
09:55summer, don't mean to rub it in, but if we had this situation in the summer it
09:58would be very warm indeed. In fact going into next week you'll see how the
10:03weather pattern next week could lead to some really quite warm weather in the
10:07summer or the spring, but because it's happening in November, mild yes but not
10:13particularly extraordinary temperatures. But the temperatures at 5,000 feet are
10:17well above average for that height whilst we've got the blues marked there
10:23towards Iceland and the fronts here acting as the boundary between the cold
10:28air to the north and the mild air to the south. And what happens through Halloween
10:34is that these fronts bring some rain and the strong winds to the north of
10:38Scotland, meanwhile the rest of the UK is basically under high pressure still. As
10:43the cold front starts to sink south later Halloween the blues start to sink
10:50south and so later and then into the 1st of November we've got the blues
10:56starting to make an appearance into the far north of Scotland. But that's as far
11:01as they get because another pulse of warm air in the Atlantic almost heading
11:07directly north, courtesy of these areas of low pressure, mean that the fronts
11:12over the UK are also deflected eventually to the north and these fronts
11:17weaken as they come south as well because higher pressure builds back in.
11:20The reason higher pressure builds back in is because of this pulse of warm air
11:24to the west of the UK that then comes in over the top of the country. Why are we
11:29getting this big pulse of warm air across the mid-Atlantic? Well I'm going to be
11:33exploring that towards the end of this and it's something to do with
11:38thunderstorms over the Pacific. But in the meantime for much of the UK it's
11:44relatively benign period. I'm just going to take a quick look at the weather
11:50summary over the next few days and what you can see with these four charts here.
11:53Pressure chart with the jet stream well to the north of the UK, high pressure
11:57building in for the rest of Tuesday. Here's the cloud map and that's the
12:00important thing because that will make a difference in terms of overnight
12:03temperatures, daytime temperatures, how it will feel. However with high pressure
12:08virtually centred over the UK these areas of cloud are just going to be
12:13floating around slowly and aimlessly with no particularly strong winds to
12:18break them up with the exception of eastern Scotland as already mentioned
12:20those westerlies across the far north of the UK are helping to break up the
12:25cloud for eastern Scotland. But elsewhere across the UK it's tenuous areas of
12:29cloud drifting here and there. Variable amounts of cloud, best way to sum it up over the
12:34next few days. The cloud will have a few spots of rain and drizzle particularly
12:38over western hills, most especially western Scotland Tuesday night into
12:42Wednesday. Temperatures yeah they'll dip into the single figures if we get
12:46cloud breaks otherwise by the start of Wednesday what 11, 12, 13 nothing
12:51particularly exciting. Now Wednesday this is two o'clock, high pressure centred
12:56over the UK, a lot of cloud but you can see some cloud breaks southeast England,
13:01northeast England, more extensive cloud breaks, sunny skies for much of northern
13:08and eastern mainland Scotland. Just some patchy rain pushing into Shetland and
13:12Orkney, that's the front making its first appearance later Wednesday. But
13:18winds are light, that's what this map in the middle is showing, light winds at
13:23this stage. Then the wind arrows start to pick up there across northwest Scotland
13:29and it's through the hours of darkness on Wednesday night, you can see
13:34these colours, these are areas of 50 mile per hour gusts or above. So just heading
13:40into the far north of Scotland, there's the jet stream, there's the frontal
13:43system, tightly packed isobars and some outbreaks of rain into Shetland, bits and
13:47pieces of rain for western Scotland. Further south it's more of the same,
13:51Wednesday night into Thursday we've got variable amounts of cloud floating here
13:56and there. Where we do get cloud breaks on Wednesday night there'll be some fog
14:00patches for the start of Thursday but yeah otherwise they'll clear through the
14:04morning. And then Thursday, this is two o'clock, so Halloween mid-afternoon and
14:12it's breezy in the north of Scotland, light winds elsewhere. Outbreaks of rain
14:16to the far north of Scotland, mostly light but some moderate rain. Front
14:20starting to sink south and some cloud breaks but otherwise a lot of cloud
14:24across the country. Temperatures 14, 15, 16 in the south, 13, 14 further north. Then
14:31fast-forwarding to Friday, similar sort of time and what you can see is the
14:36front has sunk south across Scotland, Northern Ireland. The jet stream is
14:41becoming more amplified once again but we've got colder air coming into the
14:45north so into the single figures Friday afternoon into northern Scotland. The
14:51winds are coming from the north but that brings some brighter skies so after the
14:55damp weather on Halloween, the 1st of November in northern Scotland at least
15:00is looking a little drier and brighter. The front though is coming south across
15:05central and southern Scotland, Northern Ireland. It's weakening, light and patchy
15:08rain and then it just basically fizzles out as high pressure builds back in. Now
15:13that high pressure is with us into the weekend but by Saturday it's starting to
15:20move to the east of the UK. As a result what you can see on this graphic and
15:27more so on Sunday are southeasterly winds. Southeasterly winds coming from the
15:34continent could be more reliably drier and clearer compared with the Atlantic
15:40flow that we've got over the next few days. So you can see a greater chance by
15:45the start of Sunday of some cloud breaks developing across England and Wales. That
15:49means that for southern parts of the UK, although they'll still be variable
15:53amounts of cloud coming and going through the weekend, there's perhaps a
15:56better chance through the weekend of some sunshine. Further north we've still
16:00got a large amount of cloud for Scotland, Northern Ireland, particularly Western
16:03Scotland and Northern Ireland and over the hills but some good cloud breaks
16:09there for the northeast, for Aberdeenshire for example. Temperatures
16:13dipping a little bit by the weekend. Let's take a look at temperatures
16:16actually. This is the temperature trend over the next few days and really it's
16:21spot the difference. It's low to mid-teens across most of the country. The
16:27one big difference there is Northern Scotland by Friday and in fact we can
16:33take a look at that on a graph. So London, a small downward trend in maximum and
16:41minimum temperatures through the next few days. Maximum on the top, 16 down to
16:4513, 11, 12 Celsius by the weekend. Minimum temperatures there down to the
16:51mid to high single figures by the weekend. Edinburgh, similar sort of trend
16:57really, just a couple of degrees lower but if we click somewhere further north
17:03than that, so this is a point in the far north of Scotland and you can see by the
17:08start of Friday low single figures possible. Just move the map up here and
17:15go to Shetland and yeah, mid to low single figures possible by Friday
17:21morning. Temperatures do recover in the north of Scotland actually by the
17:24weekend so although there's this gradual decrease in temperatures for England and
17:29Wales, I think for Scotland and Northern Ireland the lowest temperatures will be
17:33around Friday with that brief northerly and then as high pressure builds back in
17:38again those temperatures recover. Just want to quickly look at wind speeds as
17:43well because I mentioned that winds are peaking Wednesday night into Thursday.
17:47This is a summary for each day so the maximum wind gust for each day over the
17:50next few days but we can pinpoint the time at which those winds peak and as
17:58you can see it's 5 a.m. Thursday. Now it's picking out their exposed parts of
18:05northern Scotland but we're also likely to see, particularly through Halloween,
18:11these westerlies or southwesterlies are going to be colliding against the hills
18:17and then bouncing on the other side of the hills so that's what we call lee
18:22gusts, lee gustiness. It's where you've got stable air because we've got high
18:26pressure and so as the wind gusts push or the strong winds push against the
18:33mountains in the west they're forced up but high pressure is trying to keep a
18:38lid on activity because high pressure is sinking air and so as those winds are
18:43forced to rise over the mountains they're then forced back down again by
18:48that high pressure as they descend over the mountains to the east and that
18:53causes some buoyancy basically. They rise over the mountains, they're forced back
18:58down by high pressure and then they overshoot somewhat so they rise again
19:03and then they descend again and you get this lee wave activity so this ripple in
19:10the atmosphere and wherever the winds are descending you get a peak in wind
19:14gusts and that can happen say over eastern parts of Scotland so there's the
19:18risk basically, eastern Scotland through Thursday and early Thursday of wind gusts
19:25of 50-60 miles an hour so that's something that we'll be monitoring
19:29closely over the next few days but of course for the rest of the UK it's not windy at
19:32all, it's very light winds hence the variable cloud floating here and there
19:37and just want to talk specifically about Halloween weather because you might be
19:43making plans, you might have kids, you might be going out trick-or-treating so
19:48let's take a quick look at that. That's the wrong graphic. Still getting used to this.
19:53Please bear with me. Okay that's the one. Skipping forward to Halloween and
20:02assuming you're going out just after dark which of course at the moment is
20:06about five o'clock. Here's how it's looking across the UK. A lot of cloud basically, an
20:13awful lot of cloud. Some thick low cloud across western parts of Scotland giving
20:19some drizzle and we've got that strong wind as well across Scotland. Breezy for
20:25Northern Ireland and Northern England but not quite as strong as further north and we've
20:29got more persistent damp weather for Shetland, Orkney and the far north of Scotland, the
20:32Outer Hebrides. But elsewhere across the UK it's dry. There'll be some breaks in the
20:38cloud. There'll be somewhat random again especially in the south. You can see some
20:42breaks being picked out there for southern counties of England. Could be a
20:45bit more extensive. It's difficult to say at this stage because these breaks are
20:49going to be so tenuous and random but if we put on the temperatures you can see it's
20:53going to be fairly mild. 12 Celsius, 11, but anywhere you pick it's double figures
20:58whether you've got the drizzle or strong wind or the low cloud and so on. So mild, a lot
21:06of cloud but most places dry for Halloween. Nothing particularly spooky
21:13about that. I'll tell you what is scary though, the thunderstorms that we are seeing across
21:20Iberia at the moment and I just want to show you some of the rainfall totals
21:26that are taking place here. Now this, the eastern part of Spain is the focus for
21:39the heaviest rain and although these will be in the form of thunderstorms and
21:44heavy showers so it's difficult to pinpoint exactly where we're going to see the
21:48liveliest weather. It's really through Tuesday and Wednesday so the rest of today and into
21:52Wednesday. This is showing the rolling rainfall accumulation so as it's playing
21:56it's showing the rain adding up through time and what it's picking out there is
22:00in excess of a hundred and fifty millimetres of rainfall across eastern
22:05parts of Spain so some really exceptional rain totals and as it plays
22:12through you can see those areas getting a little bit bigger. I think that's, yeah
22:17there we go, there's a spot there that's in excess of 200 millimetres and I
22:21understand there is that risk of two to two hundred and fifty millimetres of rain
22:26accumulating and Valencia is around here somewhere. These are areas that are
22:31really quite populated so this amount of rainfall with the additional risk of
22:37tornadoes, water spouts, large hail, flashes of lightning could cause
22:43considerable impacts over the next few days because of that cut-off vortex
22:47because of the gotofria situation that Spanish call it and those slow-moving
22:51areas of showers and thunderstorms. Meanwhile there are also areas of
22:58thunderstorms across the Western Pacific. Take a look at those. There is a
23:06reason these are significant. Let's zoom out a little bit. Okay and if we go to
23:19the day, daytime, there's an area about here of enhanced tropical convection,
23:29enhanced rainfall. So we've got thunderstorms on the other side of the
23:33planet, we've got thunderstorms in Spain on Halloween. These you might say are
23:41spooky types of weather, thunderstorms, so hence the thumbnail title spooky action
23:47but at a distance from the UK. Those fans of quantum mechanics might also
23:55recognize that phrase because it's a phrase that Einstein used to describe
23:59quantum entanglement and that's the phenomenon, a really strange phenomenon,
24:04whereby subatomic particles can share the same information or observe to do
24:11the same thing but be you know many thousands of miles or light-years apart
24:17even though information can't travel that fast between the two of them
24:22they've got no apparent means of communicating between each other and
24:27they still somehow influence each other at that great distance and Einstein said
24:34that violated the law of physics that nothing can travel faster than the speed
24:39of light and so he called it spooky action at a distance. That's why I use
24:44that as the title for this week's deep dive thumbnail. Clickbait for Halloween
24:49enthusiasts and quantum mechanics enthusiasts. I'm not going to go into any
24:54more detail about quantum mechanics, you'll be pleased to know, mainly because I
24:58don't understand any of it anyway. But I thought it was interesting because this
25:02area of enhanced tropical convection is connected to the UK's weather next week
25:10but that's where the similarities between the weather forecast and quantum
25:15entanglement finish because there is a connection and it doesn't happen
25:22instantaneously, there is a mechanism by which this rain influences the UK's
25:28weather. This is a teleconnection. Teleconnections, we've talked about them
25:32plenty of times before, are things like El Nino and the quasi-biennial
25:38oscillation. There's plenty of these teleconnections that meteorologists look
25:41at and they're basically weather or climate phenomena that can happen
25:45thousands of miles away but have an influence on the UK's weather and this
25:51particular teleconnection is called the Madden-Julian oscillation. Unlike the El
25:55Nino teleconnection or other similar teleconnections, this one happens at
26:00sub-seasonal timescales, so at timescales of a few weeks to a month or two and it
26:08was only discovered relatively recently actually, back in 1971 by Roland Madden
26:13and Paul Julian. What they discovered was there's this travelling area across the
26:24globe of enhanced tropical rainfall and suppressed tropical rainfall and it
26:29slowly moves from west to east at about four or five metres per second.
26:35Here's an illustration of enhanced tropical convection over the Indian
26:40Ocean. You've got this strong upward motion which then results in this strong
26:45downward motion a thousand miles or so away over the West Pacific. Now this area
26:52of enhanced tropical convection would slowly move eastwards at about four or
27:00five metres per second and we end up with eight known phases of the Madden-
27:07Julian oscillation, that's what it's called. Phase one to eight and this
27:14basically describes that enhanced area of tropical convection as it moves
27:18around the world, it circumnavigates the world, although it's strongest when it
27:23appears in the Indian Ocean and the Pacific Ocean, it kind of loses a lot of
27:27its identity as it moves through the Atlantic and Africa and so on, but it can
27:32influence tropical cyclone activity and African rainfall. So phase one shows it
27:39starting to appear in the Indian Ocean, that's what this is showing and what
27:42you're seeing here the greens and then into the blues are where it's wetter than
27:46average and here just off the coast of East Africa we've got phase one, wetter
27:51than average weather into the eastern or the western part of the Indian Ocean and
27:55then it really through phase two and phase three it really gets going across
27:59the Indian Ocean, this big area of blue. Phase four then sees it move into the
28:04maritime continents, that's you know much of Indonesia, North Australia. Phase five
28:11shows it's really taking off across Indonesia, Borneo and North Australia.
28:18Phase six then takes it into the West Pacific. Phase seven continues its journey
28:25across the Pacific. Phase eight it tends to weaken as it moves further east
28:31across the Pacific. So we've got this traveling wave of enhanced precipitation
28:38through the Indian and then through the Pacific Oceans. Why is that important?
28:44It's important because it does all sorts of funny things to global weather
28:48patterns, it influences rainfall in California, it influences the Indian and
28:52Australian monsoons, it influences tropical cyclone activity and it
28:57increases or decreases the chance of high pressure over the UK. And that's
29:03shown by this diagram, this is a paper from 2008 by Christophe Casseau and it's in
29:09nature, you can see the full reference at the top there. Now just to summarise this
29:14very briefly because I know there's a lot to take in, this shows different
29:18weather patterns for the UK in four different columns. The left column here
29:22is the negative North Atlantic Oscillation, basically that's high
29:28pressure near the UK or just to the north of the UK to put it simply. The
29:33next column is the positive North Atlantic Oscillation, that's where we've
29:37got stronger westerlies over the UK so in the winter that can lead to more
29:41storminess, it can lead to milder and wetter winter, it's what we've seen a lot
29:45of in the last 18 months basically. Then in the third column it's the Atlantic
29:51Ridge, so a big area of high pressure across the Atlantic and often
29:54northwesterlies or northerly winds for the UK and then we've got a Scandinavian
29:58high pressure so that's where we've got easterlies or southerlies for the UK but
30:02still an area of high pressure nearby. The strongest relationship as is shown
30:08by this paper between the Madden-Julian Oscillation phase and the weather
30:14patterns over the UK are from phases, so the phases are listed here, we've got phase
30:20one which is a relatively weak phase but then by the time you get to phase three
30:24and four where the Madden-Julian Oscillation really intensifies over the
30:28Indian Ocean, what that's linked to and what that's showing here with these
30:33orange columns coming out is that you're more likely to get stronger NAO positive
30:43phase for the UK, stronger westerlies, more likely, not guaranteed by the way,
30:47there's a lot of other things going on with UK's weather, this is just one
30:52relationship with UK's weather so phases three and four where you've got
30:56enhanced tropical rainfall over the Indian Ocean you get a greater chance of
31:01westerlies for the UK rather than high pressure. The opposite is then true by
31:06the time you get to phase six and more especially phase seven and that's what's
31:10shown by this here is that as that enhanced area of rainfall moves into the
31:19maritime continent and then more especially moves through Western Pacific
31:22you get an increased chance of higher pressure near the UK, more likely to the
31:29north of the UK or perhaps directly over the UK, a negative North Atlantic
31:34Oscillation. But there's a lag effect and it's reckoned that when you get into
31:40phase six of the Madden-Julian Oscillation when it's going from
31:44Indonesia into the West Pacific, 10 days later, 12 days later, you're more likely
31:51to have weaker westerly winds for the UK, higher pressure over or to the north of
31:58the UK, more likely, not guaranteed, like I say there are lots of other things
32:02going on with the UK's weather. But what we are indeed seeing and another
32:09complicated diagram here for you but this basically shows how the Madden-
32:15Julian Oscillation phase has changed during the last 40 days and how it's
32:20expected to change in the next few weeks. The black line that goes around, I say
32:26it's a line it's more of a circle isn't it, it starts off 40 days ago 19th of
32:31September and it shows a dot in this quadrant the West Pacific. So the last
32:38time we saw enhanced tropical rainfall in the West Pacific was the 19th of
32:43September. Then it moved around the world so if you imagine it's circulating
32:47around the world going through all these different places, West Hemisphere and
32:51Africa and then down here we've got the Indian Ocean and then it's moving
32:55through the maritime continent in the last week or two and now the current
33:01time it's going from phase six to phase seven so it's well and truly in the West
33:05Pacific. So it's at this point that you can add on a week or a bit longer and
33:11say okay that's when we can expect weaker westerlies if that's the only
33:17thing that was influencing the UK's weather which of course it's not. Then
33:20into the first few days of November the phase moves into phase eight and then
33:26phase one which are typically phases that don't really influence the UK's
33:30weather so it's at that point that we can't really use it for predicting the
33:34UK's weather but we're already in phase six going into phase seven as I
33:38mentioned and so let's take a look at that and how it looks and why does it
33:50influence the UK's weather that's what I want to address basically. We've got this
33:54enhanced area of tropical rainfall now and that at the top of the atmosphere
34:02well the top of the troposphere where the weather takes place got these
34:06towering cumulonimbus clouds a tremendous amount of energy being lifted
34:12through this convective process so all these towering thunderstorm clouds and
34:17what you notice if you took a temperature reading of the upper
34:22troposphere where the tops of these clouds are is that you've got a lot of
34:26cold air up here and that's because you've got all this energy being taken
34:31from the surface and as it rises it cools and by the time it gets you know
34:37these towering cumulonimbus clouds by the time they get to the top they're
34:40very cold indeed and that's just indicative of how much energy they hold
34:43so at the top of these clouds you've got a lot of cold air and you've got a lot
34:49of energy leaving the top of the troposphere and that has a ripple impact
34:54a ripple effect on both hemispheres and in fact the jet stream of both
35:00hemispheres and one of the things that it tends to do when it's in the West
35:07Pacific and it's producing all this energy in the upper troposphere is it
35:13influences the shape of the jet stream then it's almost like these ripples are
35:17coming out and just bumping into the jet stream in the North Pacific and it
35:23leads to a more wobbly jet stream basically that's what happens and what
35:29we're seeing at the time recording is this very loopy jet stream over the
35:34North Atlantic and in particular I want to draw your attention to this diving
35:40segment the jet stream this elongated trough over western parts of North
35:44America and if we just fast forward slightly what you can see is that that
35:54then eventually has an impact on the other side of North America it's more
35:59evident in fact if I take off the jet stream and put on the temperatures what
36:05happens is this this area of warmth then pushes north over eastern parts of North
36:10America during Wednesday and into Thursday so this area this is what
36:16we're watching because of that trough digging south we've then got on the
36:21other side of North America this rising plume of warmth moving into North
36:27Newfoundland and that then squeezes this area of cold air which is basically
36:33again this dip in the jet stream as a result of that squeezing we see another
36:41one of those cut off upper vortices here and that results in the jet stream being
36:49pushed even further north across Iceland and north of the UK so here's the jet
36:56stream cut off vortex and it's at this point remember at the start I said that
37:02warm air was moving north that's because of that very elongated jet stream on the
37:07other side of the Atlantic pushing the warm air north which allows higher
37:13pressure over the UK to be reinforced so after that's temporary cold spell for
37:21the far north of Scotland higher pressure gets reinforced and the result
37:26of that is that higher pressure moves slightly east but it's here to stay for
37:31some time so all of that stems to how wobbly the jet stream is over the
37:36Pacific and that is related to that enhanced area of tropical rainfall and
37:41the beauty of this is that meteorologists can look at the phase of
37:47the Madden-Julian Oscillation and can say okay that increases or decreases the
37:52chance of westerlies or increases or decreases the chance of higher pressure
37:56over the UK ten days ahead so it's one of the tools in our toolkit but of
38:01course it's as is always the case never that straightforward with the UK's
38:05weather there are many other factors involved in determining the UK's weather
38:08so it doesn't always play out as straightforward as that but yeah I just
38:14thought that was a particularly fine example. What does all that mean for our
38:17weather going to the weekend? Well high pressure is here to stay as I said that
38:22reinforcement of the high and well just allowing the center of gravity to push
38:27further east means that the high becomes centered over Central Europe or
38:31Scandinavia and we've got this southeast of the airflow and that continues into
38:36Monday this is a 71% probability for Monday's weather and it shows higher
38:42pressure near the UK most places dry rain being kept well to the west and
38:48some cloud breaks I imagine some decent cloud breaks but as far as temperatures
38:53are concerned nothing particularly extraordinary. Fast forward to Tuesday
38:585th of November bonfire night if you're making plans for watching fireworks or
39:03whatever this is an 86% probability so looking a week ahead it's remarkable to
39:08get an 86% probability on one of these types of weather patterns and by the way
39:14the second and third most likely weather patterns were virtually identical to
39:18this so very high confidence actually into the start of next week that
39:22we'll have higher pressure to the east of the UK keeping weather fronts at bay
39:27but these weather fronts are edging closer as you can see and my Thursday
39:37you can see just some signs of some wetter weather into western parts of the
39:41UK and there are some signals now emerging in the model output that we'll
39:44see a weak front move in during Wednesday Thursday perhaps to bring some
39:49outbreaks rain into western areas but it's weakening it's moving into high
39:52pressure then well after that it becomes a little more uncertain but this is the
39:58most likely weather pattern colored up for each day out to the next two weeks
40:02so we've got Tuesday the 12th of November on the end here strong
40:07indication of these types of weather patterns which are Scandinavian high
40:12weather patterns that's what this color is throughout next week there's also
40:15this color coming into the mix that's high-pressure centered over the UK so
40:20basically all these reds or oranges are showing that there's this strong signal
40:25for higher pressure near the UK whether it's over the UK or just east of the UK
40:30we'll see but that's what the strong signal is then just a hint there of some
40:38blues returning by the 11th of 12th of November and it's at this point around
40:43middle of November that we've lost that useful signal from the Madden-Julian
40:47oscillation and so there's a good chance that's the likelihood of high pressure
40:52decreases but of course we'll keep you updated right here on the Metal Vista
40:55all of that probably more than enough from me thank you once again for joining
40:59me and join us again for another deep dive next Tuesday bye bye