- 8 hours ago
The weather patterns are switching quite dramatically, and potentially in record breaking fashion, over the next few days. A fierce area of low pressure heading towards Iceland will bring us some windy weather before intense high settles in for the weekend.
Bringing you this deep dive is Met Office meteorologist Alex Deakin.
Bringing you this deep dive is Met Office meteorologist Alex Deakin.
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NewsTranscript
00:00Hello, we are playing pressure ping pong in this week's Met Office Deep Dive.
00:05We're going from a fierce area of low pressure to an intense area of high pressure.
00:10There's also a weather warning out for the winds across the northwest of Scotland.
00:14And could it finally be cooling down?
00:17Could it actually start to feel more like October by the weekend?
00:20All of this in this week's Met Office Deep Dive.
00:23Welcome along. Thank you so much for watching.
00:25Thank you for being there. We really do appreciate it.
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00:40So you want to subscribe and then you'll never miss one of our videos.
00:43This is the Deep Dive. We do it every Tuesday.
00:47We talk for 20 minutes, half an hour about some key elements of the weather.
00:54This week, a particularly interesting pressure pattern or interesting switcheroo is going on close to our part of the world.
01:03A little bit of weather whiplash, if you like, as we're switching things around quite a bit in the space
01:09of two or three days, really.
01:11This is the setup at the moment.
01:13Very active jet stream rippling close towards the UK.
01:17It's this air of low pressure we need to keep a close eye on.
01:20It is just starting to intensify as we go through this afternoon.
01:25And watch as it pushes its way northwards, interacts with the jet stream as it crosses, especially starts to really
01:32generate a lot of isobars out of the middle of it.
01:35Really intensifying there as we go through the early hours of tomorrow morning.
01:39And if I just stop it there, 10 o'clock tomorrow morning, let's look at the central pressure.
01:44It has dropped to 937 hectopascals.
01:48That is an intense area of low pressure, particularly so for October.
01:54The October record low pressure recorded in Iceland is 938 hectopascals or millibars.
02:03Now, to be honest, that is just a little bit away from Iceland.
02:07If we take that off and zoom in, you can see that central pressure is still a little bit off,
02:12but it is still going to move up close to Iceland as we go through tomorrow.
02:18Still with a pretty deep center close by to it.
02:22In the middle there now, it is still potentially lower than 940 hectopascals.
02:29So that is a particularly intense area of low pressure.
02:32Just for comparison, the lowest pressure recorded in the UK in October is 947.9 hectopascals.
02:42That was from Storm Amy last year in Baltasound.
02:45So, yeah, that's a pretty deep area of low pressure.
02:47And for another comparison, the great storm of 87, that had a central pressure of the across the UK of
02:54953 hectopascals.
02:56So that is a pretty fierce storm in Iceland.
03:00But then we have a massive switch around because if we go from Wednesday to the afternoon to Saturday afternoon,
03:10well, now look at what we've got across the UK.
03:12High pressure dominating a big, fat, chunky area of high pressure.
03:16And if we put the pressure on that, what have we got?
03:20A thousand and thirty six hectopascals.
03:22We've gone up from the low close to Iceland to a thousand and thirty six hundred hectopascal jump over that
03:30space through the course of three days.
03:32Look at the pressure in Iceland at this stage up to a thousand and twenty two.
03:36So that is quite a remarkable switch around in our pressure pattern and actually potentially record breaking as well.
03:44These charts are taken from Polar WX.
03:49They look back at all the weather charts since 1950.
03:54This is the actual pressure chart for that low pressure for Wednesday at midday.
04:00Sorry, at three o'clock in the afternoon when it's just approaching Iceland.
04:03And the blue blobs are how close to the record for the month they are.
04:08And actually, we can see that they're going to be in that dark blue zone.
04:12If we zoom in, we can see that they are likely to be record breaking in this part of the
04:16world.
04:16Whether it actually breaks the Iceland record would require actually, you know, an observation on Iceland.
04:21But for going back historically over the charts, that would be record breaking for this part of the world for
04:26the month of October by three or four hectopascals.
04:30That's what those dark blue colours are suggesting.
04:33So potentially record breaking low close by to Iceland.
04:36And then we flip it around for Saturday.
04:38What's that high pressure?
04:39Well, these are the same charts, again, going back to 1950, comparing all the previous, looking at all the previous
04:46charts for the month of October.
04:48Now, the oranges are for a record high.
04:50The oranges are close to record.
04:51It needs to be red to actually be a record.
04:53This is the American model, which is generating 1,040 in that central high pressure across the UK.
04:59And that will be not far off the record for England, Wales and Northern Ireland, where the record's around about
05:071,040, 1,042.
05:09Not a record in Scotland, because the October record for the UK recorded in Scotland is actually 1,045.
05:15So we're unlikely to be record breaking here.
05:16And that's only if the American model's right.
05:18This is the European model.
05:20It doesn't have quite the same intensity to that high.
05:22It's projecting the high will be about 1,036, 1,037, like our model was when we got to the
05:28centre of 1,036.
05:29But again, not far off record breaking for this time of year.
05:34So some remarkable changes in our weather patterns over the next few days.
05:39Let's take a closer look at why that might be happening now.
05:43Come back to the here and now with that waving active jet stream.
05:47It's not this area of low pressure.
05:49It's this area of low pressure that we need to watch intensely as it develops.
05:52It kind of swallows this low.
05:54This is one already sitting up to the north of the UK.
05:56This cold front did bring some rain across the eastern areas through the day today.
06:00It's since swept away.
06:01Now we've got this bulge in the isobars, a little ridge of high pressure, bringing many places a fine afternoon.
06:07But let's put the pressure on here.
06:09Take those ones off.
06:11And look at the centre of that.
06:139.78 hectopascals.
06:16Now, this jet stream here.
06:18Let's take that off for a second.
06:209.78.
06:21This jet stream here, there's like a jet streak in it almost.
06:24The intensity, the darker purple colours there.
06:27A pulse of stronger winds.
06:29And the low here is in what we call the right entrance to that jet.
06:33So it is developing a little bit as we go through the next, say, six hours or so.
06:39If we fast forward to Tuesday evening and then put the pressure on again.
06:46It's now dropped to 971 hectopascals.
06:49So it's dropped, what's that, eight hectopascals, eight millibars in 12 hours.
06:56But it's really then, as we go through the night, as it crosses the jet and comes into what we
07:01call a left exit, this part of the jet, that it really does pick up.
07:06So let's show that again.
07:08Play through.
07:09Just watch how the isobars pop off, pop out of it.
07:11Pop, pop, pop.
07:12Take the jet stream off there because then you can really see those isobars jumping out of it as it
07:17crosses the jet and as it intensifies.
07:19And that's where it gets to its, you know, it's kind of peak low there at 936 hectopascals as it
07:25develops and as it intensifies on its way up towards Iceland.
07:29Now, zooming in on that.
07:33Oh, take those off.
07:36I knew I was going to do that.
07:37Let's zoom in on that because actually that central low is still just to the south of Iceland.
07:41And actually the strongest winds are in this little pinch here, as is often the case.
07:47The strongest winds are often in this southwestern quadrant.
07:51That's where the isobars are closest together.
07:53That when you get these lows that develop across the Atlantic and come in, the strongest winds are often in
07:57this quadrant of the low pressure.
07:59So even though the low itself is actually rapidly approaching Iceland, the strongest winds stay in this zone just to
08:07the south.
08:07It will be quite windy across the north of Iceland, but it's actually in here where they're going to see
08:13the strongest winds.
08:14But also it's this cold front as it approaches the UK.
08:17The isobars pinching together, not as strong as here, but we are going to see some strong winds.
08:21More on that in a moment.
08:22But this low pressure, as it then approaches, just generating the strongest winds on its southern flank.
08:27So further north across Iceland, it's actually, yes, it's going to be windy, but a bigger concern here could be
08:33some snowfall.
08:34If you put the air mass on, zoom out a little bit again, you can see that as it approaches,
08:40it's bringing up mild air as it crosses and the cold air is tucked in here.
08:47So the cold air tucked in on its northern side, it's bringing the moisture, that moisture is hitting the colder
08:53air.
08:53And so, yes, we are likely to see some, take those off, some heavy snowfall and strong winds across northern
09:00parts of Iceland.
09:02And that's reflected in the warnings that the Icelandic Weather Service have issued.
09:07They've got yellow wind warnings across the south, because as that low moves up, it will still get windy.
09:11They're talking 25 meters per second.
09:1425 meters per second is 56 miles an hour.
09:17That is not exceptional, far from it, for Iceland at this time of year.
09:22But, you know, could cause some issues.
09:24So they do have the yellow warnings in place.
09:26The amber warning, well, that's for snow, actually for blizzards, because they're going to combine in here, in that northern
09:31quarter, that northwestern quarter, with that moisture coming up, hitting the cold air and those strong winds.
09:38We are likely to see heavy snowfall across those northern portions of Iceland.
09:41So they've got an amber warning out for blizzards across that northern portion of Iceland, and the yellow warnings for
09:48winds across the south, even though it looks like a really, really fierce storm in terms of wind.
09:52Actually, potentially the biggest issue will be with the snowfall.
09:56So really quite interesting to see that.
09:59And, of course, that's just how we expect things to develop.
10:02Could be somewhat different, perhaps.
10:04This is the ECMWF Ensemble forecast for the valet time is Wednesday, midday Wednesday.
10:14And that's got the pressure pattern here in the multicolors, where the control is.
10:21But each of these little dots in here is when we run the model another time with a slightly different
10:26starting situation.
10:27And you can see it now, it's zoomed in a little bit.
10:30Each of these different dots represents the center of the low, and they're all in this kind of yellowy, like,
10:36it's like an elaborate rhubarb and custard.
10:39The yellow and the pinks here, suggesting that that low is likely to be 940, 945.
10:44Some of them suggest it could be down to 935 or in that ballpark as it approaches.
10:49So quite a strong signal that low is going to be tucked in.
10:52And as you'd expect, you know, we're only less than 36 hours away from when this low, 24 hours away,
10:58really from when that low is at its peak.
11:00But quite a cluster there, or, as I say, close to that potentially record-breaking low number in terms of
11:07pressure recorded on Iceland.
11:09But, again, that low is at this stage still a little bit off to the south, and its exact track
11:14will determine just how low the pressure gets in Iceland.
11:18But really quite interesting, I thought, to see there how that low is developing and bringing some very windy weather
11:25to Iceland, but also potentially some heavy snow also.
11:29So that low will also be impacting the UK's weather.
11:32So let's take a little bit of a look at that.
11:34I said at the start we do have a warning in place.
11:37And this is the picture through the afternoon.
11:39As I said, we're behind this cold front.
11:41There's quite a bit of sunshine around, quite a few showers moving through.
11:44If we just fast forward to tomorrow, you can see, or to this evening, the showers keep going.
11:50There's a bit of a ridge of high pressure.
11:52Put the winds on, actually.
11:53It might be quite nice.
11:54You just see those winds arching around.
11:56There's a little bump of high pressure in here, which in the south, through the early hours, light winds, clear
12:02skies, could allow a little bit of mist and fog to come in into parts of the south.
12:08So let's, yeah, in here, those light winds could see some mist and fog in this zone here.
12:14Whereas further north, that next weather system is coming in, and the winds are really starting to pick up.
12:20Let's take a look at the winds in a bit more detail.
12:23So this is tomorrow's bigger picture.
12:26There's the low heading up towards Iceland.
12:29There's the jet stream taking it that way.
12:30There's the cold front draping down towards the UK, bringing some rain here.
12:35So while most of it is influenced by high pressure, a lot of fine weather around tomorrow, it is going
12:39to turn wet across the northwest of Scotland.
12:42But it's really the winds that say that are giving us the greatest cause of concern, picking up as we
12:46go through the day.
12:47Let's take a closer look at those winds in a bit more detail, because we can see the gusts picking
12:55up, not particularly through today, but as we go through tomorrow.
12:58So these first very pale pink colours, that's in the 50s of miles and out.
13:04Then we go to the next shade in the 60s, and these darker pinks in here, that would be in
13:08the 70s of miles and out.
13:09Let's zoom in, and we can see that from tomorrow morning, those winds likely to be gusting in the 50s
13:17of miles and out in the northwestern corner of Scotland.
13:19But potentially, they do increase a little bit, and just see in there, these little pockets of 70 mile an
13:26hour gusts.
13:26Now, they are generally staying away from land.
13:29You can just about see them there, just off the side of the Outer Hebrides.
13:35But if we look closely, you can see as we go through those winds, just potentially getting closer to the
13:43Outer Hebrides.
13:43And certainly, we're in this zone where the winds are going to be in the 60s of miles and out.
13:47Now, that isn't exceptional for this part of the world at this time of year, but a couple of things
13:52we do need to take into consideration.
13:53We haven't really seen these kind of winds for quite some time.
13:57It's one of the first proper autumn blows, if you like, in the northwest.
14:02And of course, at this time of year, the trees are still in leaf, and that is a significant factor.
14:07If this were in January, we probably wouldn't have a warning out, because the trees in leaf make a big
14:13difference.
14:14It creates more resistance, more likely to cause branches to come down.
14:18So, we are expecting there to be potential for some disruption, certainly travel issues, and the possibility, you know, difficult
14:24traveling, certainly for high-sided vehicles.
14:26Some of the bridges may have restrictions on them, or potentially being closed in this part of the world.
14:31So, that is why we have this yellow warning in place, covering that northwestern corner of Scotland for those winds.
14:37It's gusting 50, 60, potentially up to 70 miles an hour, and it wouldn't take much of a shift in
14:43that low as it develops.
14:44And of course, it's got to really interact with the jet stream, so there's still, you know, something to play
14:48for.
14:49It's got to drop. It's got to go through explosive cyclogenesis.
14:52We're going from 970 hectopascals this afternoon to 940 hectopascals tomorrow morning.
15:00So, we're dropping 30 hectopascals. That's more than you need for it to be classed as explosive cyclogenesis.
15:06That needs to drop by 24 in 24, and it's definitely doing that.
15:09So, it's explosive cyclogenesis. We are going to see that intensifying, and it wouldn't take much to shift those winds,
15:13perhaps intensifying them by a little bit as well.
15:15So, we've got that warning in place for northwest Scotland.
15:18Valet from 10 o'clock tomorrow morning until 7 o'clock tomorrow evening.
15:23As for the rest of the UK, well, yes, it will be quite windy.
15:27As we go through tomorrow, the wind's picking up again in the north and the west, influenced by high pressure,
15:34though.
15:35So, yes, it could start a bit misty, but again, look at the temperatures.
15:39Mid to high teens. We've been over 20 degrees the past couple of days, and again, likely to be up
15:44into the high teens.
15:45So, really quite mild for this time of the year as we go through Wednesday.
15:50And then, if we look at the temperatures over the next few days, we can see how they are going
15:54to change by quite a bit as we go through Wednesday and into Thursday.
16:00We're going to see that drop off, certainly across the north, and that is because the cold front is coming
16:06through.
16:06So, again, if we come to Thursday's bigger picture, you can see by then the low has cleared away from
16:12Iceland up to the north.
16:13The jet stream still pushing it through the cold front on the front edge of that, and that will bring
16:18some rain as it sinks its way slowly southwards.
16:21But ahead of it, we've still got high pressure.
16:23Now, it might be quite cloudy across the south on Thursday, not necessarily as sunny as it will be on
16:29Wednesday, but we're still in the warmer air ahead of that cold front.
16:32So, here's still, again, temperature's likely on Thursday to be in the high teens, perhaps even 20 Celsius, whereas we're
16:37behind the cold front here.
16:39We're behind that cold front, so it is going to turn colder.
16:42And the cold front will win out overall, and the cooler air will win out overall.
16:47Again, if we take a look at the big picture, fast forward to Friday, put the temperature profile on, take
16:53the jet stream off.
16:54You can see that cooler air as the cold front comes through back to Wednesday.
16:58You can see that colder air just pushing away the warmth that's been sitting across us over the past few
17:06days.
17:07Cold front comes in.
17:08High pressure, though, is then building in behind it.
17:10So, that high pressure generally settling the weather down, bringing a lot of fine weather, some sunshine, but also bringing
17:16in that cooler air.
17:17So, as we go towards the weekend, we are going to see the temperatures dropping somewhat.
17:23Not spectacularly, you know, it's going to be colder than it has been, but temperature's not actually going to be
17:29too far off average.
17:30Again, if we look at the charts for the next few days, we get to Thursday, that's when we start
17:37to see the transition.
17:37Then Friday, Saturday, and Sunday, we're back in the low to mid-teens, so close to average, perhaps a touch
17:44below average,
17:45which maybe, if we look at the charts and what they're comparing to, they are, you know, a little bit
17:52below average by the time we get to Friday.
17:54So, the next couple of days, we're still above average.
17:56Then on Thursday, it could be really quite warm.
17:58It depends on the sunshine on Thursday.
18:00It might be a bit optimistic for that warmth across the east, but it does depend on how much sunshine
18:04we see.
18:05But the cooler air already in, that slice as the cold front comes down, and then everywhere pretty much likely
18:11to be a degree to three degrees below average by the time we get to Tuesday.
18:16So, not especially cold, but certainly compared to what we've seen for much of autumn, to be honest, it is
18:21going to be on the chilly side as we head through the second half of this week.
18:28How certain are we that high pressure is going to build in?
18:30Well, we are pretty confident that high pressure is moving in.
18:33It will bring a lot of places a fine weekend, but not necessarily everywhere.
18:37Just because we've got high pressure doesn't mean it's going to be dry and sunny everywhere.
18:41We've already seen it's definitely going to be a little bit cooler.
18:44But if we take a look at the ensembles, again, from the European model, fast forward it to Saturday.
18:50So, we're on Saturday.
18:51Now, again, this is where you run the model many times with slightly different starting scenarios.
18:56That's what we call ensembles.
18:57So, you get 50 different versions of the future.
19:00They don't always agree this strongly, however.
19:04So, this is a European forecast for Saturday, the 50 different ensembles, and each one of them has got a
19:09big fat high sitting very close to or right over the UK.
19:14So, it's really quite remarkable that we've got this solid agreement for Saturday.
19:18High pressure is going to be in control.
19:20So, that's going to bring a lot of dry weather.
19:21Not great news if you are after rain, which, of course, much of central and eastern England still could do
19:27with some.
19:28But there are then subtleties within these different high pressure systems.
19:32If we take number 10, for example, and number 20, and let's take a closer look at those, then you
19:39can see that they're somewhat different in the subtlety.
19:44Let's look at number 10 first, actually, and zoom out a little bit on that because it's got the high
19:49still sitting just to the north of Northern Ireland there.
19:54But with the high in here, it's going to generate still a lot of fine weather through high pressure, the
19:58air is sinking.
19:58But notice the winds, they're going to be coming around clockwise around that high pressure.
20:02They're going to be coming down from the North Sea.
20:04So, these eastern areas will be quite chilly with that wind.
20:07And there is also a little bit of an isobaric squeeze.
20:10The isobar is squeezing together the hints of a low pressure or a trough in here.
20:14That could generate quite a few showers down the eastern side.
20:17Now, if you're after rain, you might think that's great.
20:19But they're not going to probably generate a lot of rain.
20:21But it might just be, you know, showery on and off for much of the day down the eastern side
20:25with a fairly cold wind.
20:27So, don't be fooled by always talking about high pressure moving in.
20:30If you're in the east, it might still be quite grey and quite cool.
20:32But equally, number 20 may be closer to the mark, where the high hasn't shifted too far.
20:39It's still the same pressure pattern, basically.
20:41But the high is now sitting, well, probably in the Irish Sea, the centre of the high, or certainly close
20:46to Dublin there.
20:48And in this scenario, well, there will be a lot of sinking, a lot of dry weather right across the
20:51UK.
20:52And, OK, there may be a bit of a breeze, as you can imagine, with the isobars bent like that.
20:57There will be a bit of a breeze across East Anglia and Kemp.
20:59But we haven't got that troughing, so it's unlikely to be as showery.
21:02That might just be a cool, breezy, but largely dry day.
21:06So, even though the pressure pattern's rock solid, even though all the ensembles are in agreement for Saturday,
21:12there'll still be quite a big difference, potentially, in the outcomes and what the weather's actually like.
21:16I said it could be quite grey, quite cold and showery in eastern parts on Saturday.
21:21Or it could, by and large, just be a dry and a fine day.
21:24The temperature's a tad below the average.
21:27So, still quite a bit to play for in the detail for Saturday's weather.
21:30But, overall, the weather does look like settling down.
21:33And that is actually likely to last quite a while.
21:37This is the flavours of weather, different groupings of weather, if you like, for the next couple of weeks.
21:45Dates going along the bottom there.
21:48The different colours representing the most likely type of weather.
21:52And you can see a lot of dark reds in here.
21:54So, the high pressure takes control.
21:56That dark red, that maroon, would you call that maroon, is high pressure to the north.
22:00And that is what takes over through the weekend.
22:02And then likely to dominate, really, for the rest of October.
22:06Certainly, through the following week and in towards that week, the last week of October, which is half term, of
22:11course, for many.
22:12And you can see high pressure to the north.
22:14But, as we've seen, it doesn't necessarily mean it's going to be dry and sunny everywhere.
22:19Again, subtle differences about where the wind is at this time of year will make a big difference to the
22:26different types of weather.
22:27But, yeah, it does look like high pressure will be dominating as we go through much of next week.
22:32But I don't want to steal Aidan's thunder.
22:35He'll be talking about that quite a bit on the 10-day trend tomorrow.
22:39So, you can catch the 10-day trend tomorrow.
22:42Another reason to subscribe to the Met Office channel.
22:46That's about it from me for today.
22:47But I hope you've liked this deep dive.
22:49If you have, please leave us a comment.
22:51If you've got a question, something you'd like us to answer, then we can either go through it in a
22:55deep dive or we may even touch on it in a weather studio live.
22:58We do every Friday at 12.15.
23:02So, you want to tune in for that.
23:03Again, another reason to subscribe.
23:05But that is, I think, pretty much it from me.
23:08We enjoy the baroclinic bounce or the pressure ping pong or the weather whiplash, however you'd like to describe it.
23:16But some big changes heading our way.
23:18It's going to be an interesting few days of weather.
23:20As always, thanks very much for watching.