Whilst the mercury is set to rise this week, it won’t be sunny everywhere and it probably won’t last all that long. Alex Deakin looks at the reasons for the rising temperatures and the uncertainty in whether we see thunderstorms as it turns cooler.
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00:00Welcome to the 10-day trend that takes us into summer.
00:04Yes, meteorologically and climatologically,
00:06summer starts on the 1st of June on Saturday.
00:09And this year, it could well coincide
00:11with some summer-like weather.
00:13We are expecting temperatures to rise.
00:16And for many of us, we'll see some sunshine on Saturday.
00:19Now, it is going to be warming up pretty much
00:21across all parts for the rest of this week.
00:24It will be turning sunnier for many,
00:26but not everywhere is going to see blue skies,
00:30and particularly in parts of the north and the west,
00:32there will be further outbreaks of rain
00:34over the next couple of days.
00:35And then the big question,
00:37how long is the warmer weather going to last?
00:39And the short answer is not very,
00:42because for next week, we're back to low pressure.
00:45We're back to much cooler conditions,
00:47and we're back to plenty of showers.
00:49The really interesting question meteorologically
00:51is how are we going to change from one to the other?
00:55And what's the weather going to be like
00:56as we see that transition during the weekend?
01:00More on that in a moment.
01:01Let's get into the detail of how warm
01:03we're going to see things over the next few days,
01:06because this is the setup,
01:07big area of low pressure out in the Atlantic.
01:09And it's in here where things are warming up.
01:11This is called a warm sector, quite a broad warm sector.
01:15And it's in here behind this warm front,
01:17the warmer air is pushing its way up across the country.
01:21But notice there are weather fronts just dancing
01:23and dribbling their way across parts of northern Britain.
01:27And they will always bring cloud and some outbreaks of rain.
01:29So as I said at the start,
01:31it's not turning hot and sunny everywhere.
01:33On Friday, the warmth really confined
01:35to central and eastern parts of England.
01:37And let's run through Thursday and Friday really quickly,
01:40because this shows you the contrasts,
01:42bands of cloud and rain coming into Scotland
01:45and Northern Ireland,
01:46whereas for much of England and Wales,
01:47it's dry and a big temperature contrast on Friday.
01:50If we see some sunshine across the southeast,
01:53easily into the low 20s,
01:54whereas it stays cool across the northwest,
01:58only 12 or 13 here with some outbreaks of rain.
02:01Now, Saturday is the day where we'll see
02:03the most widespread heat, if you like.
02:06But again, it is mostly across England and Wales,
02:09still across Scotland and Northern Ireland.
02:11Temperatures, yes, are rising,
02:13but nothing spectacular here,
02:15maybe 18, 19 in the northeast of Scotland.
02:18But for the bulk of England and Wales,
02:20Saturday, widespread warmer weather.
02:23We could get up to 28 or 29 across parts of the southeast.
02:28The coasts will be cooler
02:29and the coasts may stay a bit misty and murky.
02:32But inland, we're looking at 24, 25 degrees Celsius.
02:35So we're likely to see the warmest day of the year so far,
02:39probably on Friday and maybe again on Saturday.
02:43Big question is, as I said,
02:44how long is that going to last?
02:45And well, Sunday may well be the day
02:47when we start to see a change.
02:50This graphic here shows how widespread
02:52the warmth is likely to be.
02:54This is Saturday's chart.
02:55This isn't the temperatures.
02:56This is the temperatures compared to average.
02:59And you can see there, red colours
03:00for most of England and Wales.
03:02We are well above average here,
03:04not so much for Scotland and Northern Ireland.
03:06Compare that to Friday,
03:08we're just a few places a little bit above average on Friday.
03:11That's the day we'll start to see the warmth
03:13depending on the sunshine.
03:14Widespread warmth across England and Wales on Saturday.
03:18How long does it last?
03:19Well, it looks as if things are turning cooler on Sunday,
03:22but there's a lot of uncertainty
03:24about the timing of things turning colder.
03:27But you can imagine from these graphs,
03:28actually we've got a cold front swinging across the country
03:31and that's what we are expecting.
03:33On Sunday, a cold front swings through
03:35and introduces cooler air.
03:37But there is much uncertainty about the position,
03:40the timing and indeed the intensity of this cold front.
03:44It could be bringing some thunderstorms
03:47as it moves across the country.
03:48So as I said, some uncertainty.
03:50Let's rewind the clock
03:52and show you why there's a bit of uncertainty
03:54and trace this area of low pressure going back in time
03:57all the way to the eastern seaboard of the United States.
04:02As I speak, it's forming out across the eastern seaboard
04:05and there's a lot of activity in the US at the moment.
04:07Again, another day with severe thunderstorms across the US
04:11and potential tornadoes breaking out.
04:14And that kind of severe weather can then impact
04:18on things high up in the atmosphere.
04:20This is the jet stream coming out of the United States.
04:24And as I say, things really could develop
04:26over the next couple of days
04:27with that area of low pressure,
04:29depending on the intensity,
04:30depending on the number of thunderstorms we see in the US,
04:33how that then interacts with the jet stream.
04:35You can almost see the jet almost kind of splitting there
04:38with two arms to it.
04:39So it gets very complicated through Thursday
04:42and then the next few days, the jet tends to drive.
04:45And it's this little trough
04:47which then develops the low pressure,
04:48which becomes the cold front
04:50that swings across the country on Sunday.
04:52It's pretty complicated.
04:54And that's why I'm showing you this
04:56just to show there's a lot going to happen
04:58in the next few days, high up in the atmosphere,
05:01thousands of miles away across the Atlantic
05:03that will determine the position of this cold front
05:06on Sunday.
05:08What does that mean?
05:09Well, it means that Sunday is the day
05:10we're likely to see the change.
05:12We are likely to see some thunderstorms
05:14triggered by the heat and humidity,
05:16but there's big question marks
05:18about exactly where and when.
05:19So stay tuned for updates
05:21because Sunday could be a very lively day.
05:23It may be one more hot day across the East,
05:26just depends on the timing
05:28of that cold front swinging through.
05:31Beyond Sunday, well, actually the weather
05:33becomes a little bit more straightforward.
05:35It's one of those slightly counterintuitive scenarios
05:37where there's a lot of uncertainty about Sunday,
05:40but beyond Sunday, we're reasonably confident
05:42in the forecast because the jet stream
05:44becomes not standard,
05:46but back to a more typical scenario
05:49coming out of the Atlantic
05:51and taking low pressure systems
05:53just to the north.
05:54So the most likely scenario
05:55for the early part of next week
05:56is that low pressure will dominate
05:58to the northwest.
05:59And of course, with the jet slipping back
06:00further south, we will chiefly be
06:03on the cold side of the jet.
06:05So for the first half of next week,
06:07certainly it looks as if it will be
06:09on the cool side and we'll see showers
06:11or longer spells of rain.
06:13And this graph shows that quite nicely.
06:15Two graphs here.
06:16The one on the top is for Reading
06:18and the one further down
06:20to the bottom there is Edinburgh.
06:22Now, I just really want you to focus
06:23on the red blobs.
06:25That's the most likely maximum temperatures
06:27as we go through the next few days
06:29and into next week.
06:30The dates there along the bottom,
06:31this red line is the average temperature
06:34for the time of year and the red nodules
06:36suggesting the temperature spread
06:38for the next few days.
06:40So we can see here for Reading,
06:41the temperatures are expected to rise,
06:43probably peaking on Sunday
06:45before we see a drop in temperatures.
06:46And for much of next week,
06:47temperatures are expected to be below
06:50or at or below average.
06:51And the same goes for Edinburgh.
06:53You can see that trend here,
06:54the rising and the dropping
06:56of those temperatures.
06:56So the scenario is warmer weather,
06:59yes, for the next few days,
07:00peaking probably on Saturday
07:03and then turning cooler
07:04next week with showers.
07:06May turn a bit warmer, a bit drier
07:08towards the back end of next week.
07:10But I think you'll agree there's plenty
07:12to get through before we get there.
07:14The best thing for you to do is to stay
07:16tuned to the updates
07:18down at the Met Office app
07:20or follow us on social media
07:21to see just how hot you could get
07:23on Saturday and to see if there will
07:25be some big thunderstorms around
07:28on Sunday.
07:29Thanks for watching.