10 Day Trend 04/09/2024 – Summer for some, soggy for others
This is the Met Office UK Weather forecast for the next 10 days 04/09/2024.
Huge contrasts across the UK during the next couple of days, summer for some but with heavy rain for others.
Bringing you this 10 day s weather forecast is Aidan McGivern.
Huge contrasts across the UK during the next couple of days, summer for some but with heavy rain for others.
Bringing you this 10 day s weather forecast is Aidan McGivern.
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NewsTranscript
00:00Hello and welcome to the Met Office 10-day trend. Meteorological autumn may have begun
00:05but if you live in Western Scotland, Northern Ireland or North West England you may be forgiven
00:10for thinking you've entirely missed meteorological summer. And that's because summer 2024 in
00:17the North West of the UK was considerably wetter than average. The blue colours on this
00:23map show how rainfall was above the 100% of the average for summer across Western Scotland
00:29in North West England and parts of Northern Ireland. And in some spots across North West
00:34Scotland we saw 1.5 times, 150% of typical summer rainfall. It was also considerably
00:42cooler than average in the same locations. And in fact, although this map shows how the
00:48average maximum temperature through summer compared with the 30-year average, if you
00:53look at the day-to-day maximum temperatures, some parts of Western Scotland, Kinlochew,
00:59Achnagart, didn't see a temperature reach 24 Celsius throughout June, July and August.
01:06That compares with May when those same locations saw temperatures above 25 degrees. Better
01:13late than never, you might say, this Friday could see temperatures higher across parts
01:19of Western Scotland and even parts of Northern Ireland compared with the entire summer season.
01:24Highest temperatures perhaps since May or a smaller chance, the highest temperatures
01:28in some spots of the year so far. Here's what's happening. The jet stream at the moment
01:34is extending south across the UK. A very elongated set-up and when it elongates this much it
01:39can cut off from the main flow into a entirely separate circulation. This is known as a cut-off
01:46low and you get an upper low and a surface low just to cut off from the main flow of
01:52the jet stream. So just meandering erratically around separate from the main flow and therefore
01:58getting stuck somewhere. Now, earlier in the week if you watched the week ahead forecast
02:02there was some uncertainty about where this cut-off low would end up, whether it would
02:05be to the east of the UK or to the south with very big differences across the UK as a result.
02:12It looks very likely now that it's going to be cut off and it's going to stick to the
02:16south of the UK through Thursday, Friday, Saturday, Sunday and even into Monday. That
02:23means some very heavy rainfall just to the north of that pushing into southern parts
02:29of the UK for several days in a row. That's of key concern in the next few days and those
02:37spells of rain are going to add up and they're going to cause some impacts. This is the rainfall
02:43on Thursday afternoon, heavy, persistent and some thundery outbreaks of rain moving up
02:49from the near continent and affecting South Wales, parts of West Country, South West England,
02:56South Coast and this is 4pm on Thursday but really fast-forwarding after that it continues
03:03to be wet across the same locations. The rain ebbing and flowing but essentially further
03:08spiralling bands of rain pushing north across southern counties of England. Easing off for
03:13a time for South Wales but really south of the M4 Corridor that's where the wettest weather
03:19is expected to be through Thursday and into the start of Friday. Then by Friday afternoon
03:24another spell of rain moves north across these same areas. I wouldn't take the location of
03:29these rain bands too literally, it all depends on the instability over northern France for
03:34example and how thundery outbreaks of rain develop there and those can be very uncertain
03:42in the computer modelling and therefore it's a little uncertain at the moment in terms
03:47of exactly where we'll see the heaviest rain but this is the total rainfall through Thursday
03:52and Friday. The key over here on the right and just indicates widely, 50-60mm across
04:00Devon, Cornwall, Somerset, into Dorset, parts of Hampshire for example and in some places
04:07more than 100mm through that period. In fact one or two spots could see 100mm or so in
04:14the space of 24 hours on Thursday and then a few other spots, not necessarily the same
04:19locations could see again 100mm or so on Friday and that amount of rainfall across southern
04:25parts of the UK could cause some impacts, localised flooding, river flooding and transport
04:30disruption so yellow rain warning in force for Thursday and Friday. Stay up to date with
04:35the latest updates on that through the Met Office website and app. Also some rainfall
04:41starting to accumulate later Friday further north of the M4 corridor as these bands of
04:46rain start to move north once again but initially the main cause for concern is south Wales
04:51into the south of England, especially West Country and the south-west. Why is the rain
04:58going to be so heavy? It's because of instability in the atmosphere because of the cut-off upper
05:03low and the surface low over France and also a lot of humidity present in the atmosphere.
05:08Now this is the time of recording, Wednesday, relatively cool air across the UK but as that
05:14low pressure forms over France we're going to see this circulation drag very warm and
05:19humid air from central Europe over the North Sea and into the UK so those colours turning
05:24more orange as the days progress over the next few days. Easterly winds, yes, but not
05:29cold easterly winds by any stretch of the imagination, this is humid air returning to
05:33the UK and that not only will lead to those heavy outbreaks of rain across southern parts
05:39of the country but it will also lead to extensive cloud cover, thick layers of cloud in the
05:43south where we've got that heavy rain as well as some hill fog and coastal fog in the south
05:47but not only that, across eastern parts of the UK, especially north-east England into
05:52eastern Scotland we're going to see fret and ha, a lot of low cloud just persisting along
05:57that east coast and perhaps a few miles inland as well. Low cloud, mist and murk persisting
06:04through Thursday and Friday. A stark contrast compared with western Scotland and northern
06:09Ireland, north-west England where the cloud will be well broken up by Friday and lengthy
06:14swells of sunshine will develop and that is reflected in the temperatures. So not only
06:19have we got the humidity and the sunshine on Friday, we've also got the fern effect
06:25where the air dries up over the hills to the east and then as it descends again, drier
06:31air, it's warmer and allows temperatures to reach into the mid-twenties. If we see twenty-five
06:37degrees or so in some of those locations I mentioned earlier then it would indeed be
06:41the warmest day since May. So, twenty-four, twenty-five degrees, twenty-three there for
06:47northern Ireland but high teens where we've got the mist and low cloud along the east
06:52coast. It's not just the north-west we'll see the warmest air, it's also likely to be
06:57relatively warm through parts of north Wales into the midlands, east Anglia for example,
07:01twenty-five to twenty-seven Celsius on Friday. So for some on Friday a return to summer-like
07:08warmth but for others some very wet weather indeed in the south and you can see that contrast
07:15on Friday in the temperature compared with average map here. This is compared with the
07:19September maximum temperature average considerably above average through central and north-western
07:25parts of the UK closer to average in the north-east and more especially the south. Now, it's worth
07:31bearing in mind that there's essentially a knife-edge gradient there between the clear
07:37skies, humid and very warm weather if the sun comes through, temperatures in the twenty-five,
07:42twenty-six, twenty-seven range across central parts and the very wet weather across southern
07:48areas. And with that added uncertainty about the exact position of the bands of rain in
07:53the south, I would bear that in mind because if you're in some of these areas, say across
07:59south Wales to Bristol, just round north of the M4 where there's that boundary nearby,
08:08then whether you're on the very warm and sunny side or whether you're on the very wet side
08:13will make a huge difference and the margins are very fine indeed. So your weather app
08:21might oscillate every few hours depending on whether it's putting the rain band in one
08:27position or the other and it will only be a matter of miles whether you're in that wet
08:31weather or in the very warm weather. So that's something to bear in mind if you live in that
08:37boundary zone where it's, well, wet on one side and very warm on the other side. Likewise
08:44temperatures overnight are likely to be considerably above average, especially across northern
08:50parts of the UK. So some very warm nights coming up heading into the weekend and we
08:55keep a lot of that cloud cover. Once again on Saturday morning across north-eastern and
08:58eastern parts of the country, I think the rain easing off for a time on Saturday, perhaps
09:03a drier interlude in the south but further wet weather is likely to come along later
09:08so temperatures recovering for a time, likely to stay very cloudy and drizzly across southern
09:13counties of England, especially the south-west, perhaps south Wales, whilst again Western
09:18Scotland and Northern Ireland are seeing the best of the warm sunny spells. Into Sunday
09:23another band of rain moves north. This time it moves a little further north into central
09:27parts of the country. Again, heavy outbreaks of rain but a little bit of uncertainty about
09:31exactly where this rain band will end up. Drier northern England, Scotland, Northern
09:36Ireland, still some mist and drizzle around the north-east coast. Less warm I'd say by
09:41Sunday across Western Scotland and Northern Ireland. The winds are starting to change
09:46direction, starting to pull a bit more cloud in but staying largely dry. Now I mentioned
09:52the uncertainty about the distribution of the rain again through the weekend and it's
09:57even more uncertain unfortunately across central and southern parts where we'll see the
10:01heaviest outbreaks of rain through the weekend and the largest rainfall accumulation. Some
10:05areas again seeing 50-75mm of rain through the weekend but different weather models have
10:12slightly different locations for that rain. So the American model there has it more across
10:17southern parts of the UK. The European model has it further north into parts of mid Wales,
10:21the Midlands for example, East Anglia, whilst the Met Office model has it somewhere in between.
10:27So that's something we'll keep a close eye on and hopefully we'll be able to update you
10:31a bit more in the next couple of days. Either way the trend through Sunday and into Monday
10:35is for the wetter weather to start to move towards the south-east. Could be further heavy
10:40downpours across East Anglia and the south-east into Monday as that low moves away. But by
10:46this stage there's a big change in the bigger picture. With low pressure to the east and
10:51higher pressure to the west we're going to start to see northerly winds. And this by
10:57Tuesday to Thursday 12th September is the most likely weather pattern coming out of
11:03all the different computer models and relatively high confidence about this. Low pressure to
11:06the east, higher pressure to the west and much cooler northerly winds. These are the
11:11temperature anomalies, minus 4, minus 3, that sort of thing. And with that northerly wind
11:16we're likely to see quite a number of showers coming into northern and eastern Scotland
11:20in particular, north-east England for example. Drier towards the west and the south but feeling
11:27considerably cooler everywhere, particularly following the relatively humid air that we'll
11:31see over the next few days. But at least it will be drier in the south even if it's wetter
11:36towards the north-east. Then a bit of uncertainty heading into the following weekend as is naturally
11:41the case 10, 11 days ahead. But it looks fairly likely that we'll see a return to Atlantic
11:49weather dominating with low pressure arriving and that bringing spells of rain into the
11:54north-west and winds switching to more of a south-westerly rather than a north-easterly.
12:01That shows up quite well in this chart. Now this takes a bit of explaining but this essentially
12:06tells us whether northerlies or southerlies are most likely each day through the next
12:10two weeks. Northerlies are coloured in blue, southerlies are coloured in red. This takes
12:17up many different computer model runs from 50, 100 different models and it shows on the
12:24top row there the most recent output from all those different models for each day, whether
12:28the blues are showing up strongly, that means northerlies are very likely, that's the middle
12:32of next week for example, and then they switch to southerlies from mid-September. And the
12:38previous model runs are all listed below so you can see there's that consistency from
12:43blues, middle of next week, to reds, middle of September. This next chart shows a similar
12:48thing but instead of northerlies and southerlies it's westerlies or easterlies. And the westerlies
12:54are coloured in blue this time so some westerlies around – is my alarm going off? Beg your
12:58pardon – some westerlies around the – or easterlies for example, some week easterlies
13:05around the middle of the week next week and then back to westerlies. So south-westerlies
13:10is essentially the main theme from the middle of September. And just to finish up with the
13:15temperature trend for two relatively different locations across the UK, Southampton and Glasgow.
13:21Glasgow shows this especially well, this increase in temperatures, the red boxes there going
13:26above the average line through the weekend as that warm air comes in from the east. Then
13:32this sudden drop around the middle of next week to below average before a recovery towards
13:38average around the middle of September as those south-westerlies return and as low pressure
13:44returns from the Atlantic. Southampton, similar trend but it's not going to be quite as warm.
13:50Temperatures won't be quite as far above average through this weekend because of those spells
13:54of rain and the increase in cloud. So big swings in the weather over the next 10 days
14:01but of course for day-to-day updates we'll keep you updated right here on YouTube. Bye-bye.