• 3 months ago
This is the Met Office UK Weather forecast for the next 10 days 17/07/2024.

The heat will build across southern and eastern areas to end this week, but will there be a heatwave and how long will it last?

Bringing you this weekend’s weather forecast is Annie Shuttleworth.

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Transcript
00:00The heat is building across southern areas to end the week, but it's unlikely to last
00:05many more than three days of this 10-day trend, as we'll then return into the cooler, more
00:10unsettled set-up we've been in so far this July.
00:14The reason we've been in that set-up, well, we've been on the northern side of the jet
00:17stream.
00:18Here's the jet stream here sweeping across the Atlantic, and over the next few days,
00:22its position will change.
00:23It becomes a more amplified pattern, diving down well to the south of the UK and taking
00:29low-pressure systems up to the north and west of the UK.
00:33But as we head towards the weekend, Sunday most likely, the return of the stronger jet
00:38core to affect the UK.
00:41So it is going to turn a bit more unsettled by Sunday and certainly cooler again.
00:46But before then, as the jet stream dives down to the south, that will allow more of a southerly
00:51wind direction, and that will allow us to tap into this warmer continental air, the
00:56warmest direction at this time of year.
00:58So the heat will build, likely peaking on Friday before a weather front sweeps across
01:03the country, introducing that fresher air from the north and west by Sunday.
01:07So a bit of a change to come through the weekend.
01:10But before then, we do have that heat to build.
01:13So it's only really going to build across south and eastern areas of England and Wales.
01:18Actually, to the north and west, weather fronts are still going to affect these areas, bringing
01:22cloudier skies and outbreaks of fairly light rain, but fairly persistent rain.
01:27So as I said, in the peak of the heat, we could see 28 degrees on Thursday.
01:31That's probably the highest temperature we'll see on Thursday.
01:33But widely across England and Wales, we'll be in the mid-20s, 25 degrees is quite likely
01:38even across southern areas of Wales and some northern areas of England as well.
01:43But where that cloud still lingers, we'll still be in the higher teens, possibly the
01:47mid-teens across the far north and west.
01:49And there is a bit of a breeze up across northwestern areas where we're closer to low-pressure systems.
01:54Very little change as we head into Friday, apart from the fact that we'll start to see
01:58that heat build even further, with strong sunshine expected quite widely across England
02:04and Wales.
02:05Very high UV levels as well.
02:07The rain will potentially be a slightly more restricted to further north and west, bringing
02:11some drier weather to parts of Northern Ireland, Northern England, much of Scotland.
02:15But there will be quite a bit more cloud around here, so potentially a little bit warmer extending
02:20further north across northeastern areas of England.
02:23And Scotland's still staying largely dry and seeing temperatures into the low-20s as
02:27well.
02:28But it will be all that bit breezier further north and west.
02:31But looking where the heat really builds, you can see that as the oranges and reds start
02:35to arrive on the map, potentially 31 degrees is possible for the greater London area, but
02:41quite widely we'll be in those high-20s across many central and southeastern areas of England
02:47as well.
02:48So, a very warm or hot day to come on Friday.
02:52And then we're into that transition period Friday into Saturday.
02:55So, the further west you are, the more likely you are to see that breakdown into the cooler
02:59weather earlier on in the day.
03:02There's potential for a bit of a thundery breakdown as well, either across parts of
03:06the southeast of England, but also where this weather front lies.
03:10We could see some very heavy bursts of rain.
03:13Becomes more and more likely as the day progresses.
03:15There is some uncertainty on the timings of this weather front, so that's something to
03:19keep up to date with over the next few days.
03:21But ahead of the weather front, we've still got that heat, highs of around 29, possibly
03:2730, if the weather front stays at bay for just long enough for that heat to build a
03:32bit more widely across eastern areas.
03:35But I think that fresher feels going to arrive as the day goes on from the west when we back
03:38down into the high teens, low 20s, a bit closer to average for this time of year and certainly
03:44fresher than it will have been for the end of this week to end the weekend.
03:51So, are we going to have a heatwave this week?
03:55Well, first of all, let's have a look at the heatwave definition.
03:59Well, the heatwave definition depends on the threshold temperature for the region.
04:04So quite widely across the UK, that's 25 degrees.
04:07But as we get closer to the Greater London region, it increases up to 28 degrees.
04:12Now, you don't just need to see your heatwave threshold temperature for one day.
04:16You need it for three days in a row for it to be defined as a heatwave.
04:22Now, the heat is most likely in the south and east and any heatwave potential is really
04:28only restricted to southeastern areas.
04:30So we need to zoom in on the south and east and we'll take 28 degrees.
04:34That's our highest threshold temperature as an example.
04:38So Thursday is when that heat is starting to build.
04:41The probability of 28 degrees, if you look very closely, you can see it's only restricted
04:47to London or the Greater London region.
04:50Outside of that, we will probably see some of those 27 degrees just where those thresholds
04:54count.
04:55So that could be our first day of the heatwave, but only really for just a couple of locations.
05:02And then Friday, well, that's when the heat is likely to peak.
05:05So there's a much greater probability of seeing that 28 degrees or more, 30 or 31 degrees
05:10is actually likely on Friday for a wider region of southern and central England into
05:16parts of South Wales as well.
05:20So again, it's this Greater London region where we could be having our second day of
05:25the heatwave by this point, but we need that third day.
05:28So by Saturday, we're starting to see that cooler air arrive from the west and that.
05:34And so the heat will slowly start to push further east as we see that cooler air arrive.
05:41And so there's the potential to see another 28 degrees, but that probability is getting
05:46lower as we head towards Saturday.
05:48So there's potentially about a 50% chance that we could see that 28 degrees for the
05:53Greater London area and some southeastern areas.
05:56So I think a few locations across the south and east could technically see a heatwave.
06:00But for most of us, it's going to be one or two days at best of that heat before the
06:05cooler air arrives for the latter part of the weekend.
06:09And that's because this weather front will be pushing its way eastwards through the country,
06:14bringing in this fresher air and this more northwesterly regime.
06:17We do see a ridge of high pressure for a time on Sunday, but then as we head into the start
06:22of next week, we return to low pressures sweeping in.
06:25And that's that jet stream returning, moving us into a more changeable setup once again.
06:32But we have got the Azores high starting to build in from the south and west.
06:37So it's not going to be all wet and windy through next week.
06:40Actually, the most likely regime for Monday and Tuesday next week is for this Azores high
06:46to extend its influence at least across southern areas of the UK.
06:51We could see eastern areas still holding on to that wetter weather clearing away from
06:55the weekend.
06:56But a ridge of higher pressure just for a couple of days, Monday and Tuesday, is looking
07:01fairly likely.
07:02However, it is a northwesterly direction, so it's unlikely to be anywhere near as hot
07:08as we're expecting to end this coming week.
07:12And then, as I said, it's going to change again.
07:15So turning more changeable.
07:16Yes, we will see ridges of higher pressure, but we could see some low pressure returning
07:20as well.
07:21We get to Thursday the 25th of July, low pressure is moving in from the north and west, returning
07:27to that more unsettled picture.
07:28So I think westerly wind directions will dominate through much of next week.
07:32We could see this high pressure building in from the south and that low pressure building
07:37in from the north.
07:38So more unsettled weather is probably most likely across northwestern areas, more settled
07:42weather sometimes across southern areas.
07:44And we'll be battling between those two setups through much of next week.
07:48Here is the map for the probabilities of the different regimes for much of next week.
07:54Blues show that lower pressure and the yellows and reds show the higher pressure.
07:58So here we are to end the weekend, Sunday the 21st of July.
08:03We've got those blues moving in, that's low pressure moving in, that cooler regime moving
08:08in by Sunday.
08:10Then Monday and Tuesday, the yellows arrive.
08:13Now this is the Azores high, so that's that south, the more settled weather arriving from
08:18the south and west.
08:19Then we move back into more unsettled weather, low pressure dominating again, more of a northwesterly
08:25coming in to end the week, Thursday and Friday.
08:28So we'll be oscillating between troughs and ridges, lows and highs through next week.
08:33So potentially some more settled spells.
08:36And as we've seen for this week, it doesn't take much for us to build the heat just for
08:41a couple of days, but it doesn't look like we've got anything particularly prolonged
08:45or summer-like on the way for the next 10 days away from the next few days.
08:51But you can find out all the details on your forecast for the next couple of days and further
08:56ahead by subscribing to our YouTube channel.
08:58See you soon.
08:59Bye bye.

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