- 3 days ago
Technical Brief-20260611_111538-Meeting Recording
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00:02Right, thanks, Craig. Good morning, everyone. So, this was the analysis at six o'clock this
00:05morning. We've got a fairly unsettled picture across the UK, as you can, as you're no doubt
00:10well aware. For the next couple of days, we've got a frontal system now moving across the
00:16UK. Slightly complex in the sense that there's an occlusion on the sort of outer structure
00:22which wraps into the parent low of the Atlantic. A little bit tricky to find, even on the analysis
00:28in terms of surface ops, but when you look at the radar display, and in fact, I'll bring
00:32that across now, this is becoming less evident as well, but you can kind of make out just
00:37about a couple of maximum in the precip structures, and that's related to both the outer occlusion
00:43and then this inner frontal wave, which becomes pretty mature, and the whole thing will consolidate
00:49into more of a standard warm sector and occluding depression as we go through the course of
00:53the next 12 hours or so. So, this is moving east across the UK. It's displacing yesterday's
01:00showers out into the North Sea and over towards the continent, clearing all but the far northeast,
01:06although by now, even the kind of remnants of the showers are just about cleared to Shetland.
01:11So, it's all about the deteriorations from the west as this frontal system moves across.
01:16There's a trailing cold front, which links back to this anchoring depression in the North Atlantic,
01:24and as this depression moves east in quite strong zonal flow, this low will kind of anchor the cold
01:30front across southern parts, and it'll become increasingly prone to waves, and the detail of the
01:35waves leads to a little bit of uncertainty, certainly around the, or particularly around the boundaries
01:40of where these frontal waves form. This depression, as I say, elongates eastwards, so this will be the
01:47main feature across the North tomorrow, and there's a little bit of a change of type which takes place
01:52as we go into the weekend, and I'll come to that in a second. Here's the upper air loop, so
01:57you can see
01:58it's a bit of a messy pattern. This was the complicated vortex from yesterday with the number of shortwave
02:05features revolving around it, and that's now been well displayed eastwards by this broad upper ridge,
02:10and the upper ridge itself has been thrown up ahead of the frontal system, with a lot of warm air
02:15being pumped northeastwards across the UK, helping to build your potential height. To the northwest of
02:21the frontal zone, we've got the main jet axis, now sort of, well, on the northern side of the frontal
02:27zone,
02:28there's a little strip of shear vorticity which is running across Scotland at the moment. That's just
02:33helping to pep up precip on the occlusion at the moment, but over the next few hours, this will
02:37overrun the occlusion and lead it to weaken, and the system further south, although we'll bring the
02:43radar back again, you can see it's sort of fairly active. The main driving mechanism across the majority
02:49of this area is all warm advection, because quite a strong thermal gradient, dew points in the warm sector
02:55around 13, 14, so later this afternoon, should we see any cloud breaks developing,
02:59it'll likely feel quite humid in that air mass. To the west, there's a number of little short wave
03:04features, and you can just about make out this developing frontal wave in the imagery, and this,
03:12as the pattern is increasingly confluent, as the frontal zone moves towards the UK, it'll become
03:16increasingly prone to these waves, but in general they'll be on the warm side of the jet, so not
03:20developmental, but as I've already mentioned, they are posing some difficulties for the evolution over the
03:27next 36 to 48 hours. Here is the upper vorticity, or relative vorticity in 300 millibars, showing the
03:35upper air, so there's that short wave trough at 12 Z that's moving and clearing away. There are
03:41further elements of forcing across the north, but not a huge amount of advection through them, so not
03:45likely to be too influential. The main dominant feature is the broad scale, which as I've already
03:50mentioned, and then as we go into tomorrow, you can see the pattern becomes increasingly confluent
03:54at the surface, didn't mean to click that surface, there we go, you can see the occlusion going
04:02through, leaves the legacy of this trailing coalfund, and here's that main frontal wave, which by
04:06six o'clock in the morning, pretty much bisects country in two with southern areas in the warm sector,
04:11with lots of low clouds, bits and pieces of rain and drizzle on western hills, and further north a
04:17returning polar maritime air mass under a weak ridge, so quite a lot of moisture and some showers for
04:22western hills, but some clearer spells further east and generally sort of fine. Jumping out a little
04:27bit, so I just wanted to show the comparison between the six of GM and the midnight EC, and you
04:33can see
04:33already at that stage, there are some differences in terms of the structure within those waves, so it
04:37will make some differences to the regional detail, particularly across the centre of the UK, both in
04:42terms of precip distribution and also any cloud breaks to the east of high ground, but by the time we
04:47get 12 to tomorrow, that frontal zone or that frontal wave is starting to clear eastwards and
04:52that's sort of well agreed upon by ourselves and ECMWF, and then that, as it clears eastwards, the
05:00background occlusion from the kind of parent depression which is out in the Atlantic tomorrow,
05:03if I wind that back, you can see kind of that originates below, that swings east to bring more
05:08organised rain and showers into the northwest tomorrow. So in terms of sensible weather over the next couple
05:13of days, well, yeah, it's a fairly straightforward picture today. Bands of rain moving east, the
05:21heaviest rain clearing eastwards this afternoon to leave a legacy of a lot of cloud with some outbreaks
05:26of rain and drizzle. The amount of orographic uplift across Wales is a little bit of a slightly
05:33contentious at the moment. If we go to, you know, sort of 9, 12, the models do indicate quite a
05:41bit of
05:41orographic rainfall across west Wales, which at the minute is struggling to get going. I mean,
05:46there's some across northwest Wales at the minute, but it could well be that that aspect's a little
05:50bit overplayed. That's good in a sense, because it'd be worse if it was underplayed in the models
05:57and we had heavier rain in this region, and in terms of warnings, you might be a little bit more
06:01concerned. But as it goes, even the amounts of rainfall on offer in models across west Wales,
06:06which seems to be the most reliably the highest focus, aren't of concern. So, that's an oblique
06:12way of saying there's no warnings today, no warnings planned, and no warnings planned going
06:16forward either. It's just carrying on this story. Rain continues east, a lot of cloud. It could well
06:23be some breaks to the lee of high ground, and if we do see some breaks this afternoon, you can
06:27see
06:28it's quite a moist air mass for theta W of around 14 degrees. That could well allow temperatures to
06:33briefly get into the high teens, 19, possibly even a 20 if all the stars align.
06:43But elsewhere, temperatures generally suppressed, and overall, it's a little bit cooler than average,
06:48given the uncertain nature of the pattern. And the other feature, as well as the strength of the
06:51winds at the moment, go back to the observations, we've got some reasonably strong gusts across
06:58parts of west Wales and southern coasts of England. We'll continue to see that as a feature through the
07:04course of today, and as the frontal system continues eastwards, those strong winds, certainly in terms of
07:10leeway activity and gusts over high ground, will become a bit more extensive. So, fairly breezy
07:15conditions developing. And then as we go into this evening, yeah, the showers continue, as I mentioned, in that
07:21return in polar maritime MS across mainly western coasts and hills. It'll become generally drier than
07:28we've seen prior to this over the course of this evening. And then Friday itself, well, starts off
07:34relatively quiet, still a few showers in the northwest, some clearer spells further east, but that next
07:38frontal wave sort of maintains the largely cloudy picture, which then sort of moves eastwards through
07:44the course of Friday morning. Into Friday tomorrow afternoon, quite a few showers get going across
07:50northwest, associated with that occlusion debris starting to come in. Meanwhile, further south,
07:54a slow south-eastward clearance of clouds, some uncertainties about how quickly it breaks up,
07:59and that's due to the uncertainty with respect to the frontal wave. But should it clear up,
08:02it does still leave a legacy of a pretty moist air mass, and forecast profiles in here are relatively
08:08unstable. Not deeply unstable, because the jet axis is still to the north, but still scope for a few
08:13sharp showers to develop across parts of the Midlands, perhaps northern England, during tomorrow
08:17afternoon before they'll decay away during the evening. Then you can see that more organised
08:22rainfall associated with some slightly stronger winds getting into the north and west. In terms of the
08:27further outlook, so you may, if you're on yesterday, we talked about this. If it's the first day for a
08:37little while, you may be aware that we had been talking about potential for some very warm weather
08:43developing over the weekend. Last couple of days now, that really looks kind of off the cards,
08:48and the reason for that is due to the build of high pressure, which is still signal in the models,
08:54actually taking place a little bit further south and then west initially. So, by turning it to the
08:59weekend, that acts as high pressure is to the west rather than being to the east, and as a result,
09:04we drag in colder air from the north rather than this warmer air mass from the south. So,
09:09in terms of the actual weather, Saturday sees a continuation of showers in the north, particularly
09:15the north-west. To the south of all of that, it's a largely fine day. We've got a legacy of
09:20that cloud across extreme south and south-west, which obviously there's some slight north-south
09:25uncertainties with that position, but for the King's birthday fly-pass across the south-east,
09:30conditions look set fair. There'll be some stronger winds and showers in the north, but across
09:34England and Wales, plenty of sunny spells, and any cloud around that is around should be fairly
09:39high-based. And then into Sunday, high pressure begins to become increasingly more dominant.
09:45Still scope for a few showers across northern and eastern parts, but the majority of the country
09:48set fair. And then beyond that, yeah, high pressure dominates for a little while, but we do start to
09:54see a return of Atlantic-based weather from the early to mid part of next week, turning a bit more
09:59unsettled again. And it's beyond this point where things become a lot more uncertain due to the
10:07usual thing at this time of year, whether the pattern becomes much more amplified and we drag in
10:11warmer air from the south, or whether it ends up flattening out and become more zonal and we end up
10:16with the Atlantic pattern dominating. And as a consequence of that, the trends in the ensemble are
10:23similar to this, but I'll show you what they do look like in a sec. But the reason for showing
10:27these
10:28earlier runs is just to temper things a little bit because if you look at the like Saturday to
10:33Monday period in the ensemble here from a run that was two days ago, you'd kind of be looking at
10:39warming up and potential for extreme temperatures. And obviously that was the story that was being
10:45suggested two or three days ago. But obviously when you look at that in the latest ensemble runs,
10:51that turf Friday to study period and hopefully it'll load up fairly quickly. There we go. You can see
10:59how it's, the spread has flattened out and we're looking at average temperatures. And the reason I
11:04bring that up is obviously as we look to mid to latter part of next week, we've got that signal
11:07developing again, which you could interpret as, you know, increasingly likely to become warmer with
11:12potential of heat waves. And I suppose that is the story at the moment, but just temper that with
11:17the caveat that at the bottom end of the spread, temperatures are on the pleasant, pleasantly warm
11:24side, but nothing extreme for time of year. So that's it for me, Greg. How about you?
11:32Lovely. I'll just stop the recording.
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