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This is an in-depth Met Office UK Weather forecast for the next week and beyond. It suddenly feels like spring with temperatures widely above average for the time of year and as high as 18 Celsius in some places by Wednesday. But will it last? Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
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00:00It feels like spring has sprung, but will it last? And when is spring supposed to spring anyway?
00:08Is it particularly early at this time of year or what we might expect because of a warming climate?
00:14Those questions and many more answered in this week's Met Office Deep Dive.
00:18Welcome along. We do these in-depth looks at the weather and climate across the UK and around the world
00:23every Tuesday.
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00:38At the time of recording, we are 26 subscribers away from hitting that 400,000 milestone.
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01:01to do more of these kinds of videos.
01:05Now, before I go on, let's talk about seasons.
01:09There are lots of different definitions of seasons.
01:11You've heard many of them before. I won't go into it in too much more detail.
01:15You've got the astronomical seasons. By those definitions, astronomical spring starts on the 20th of March.
01:23That's the equinox this year.
01:25We've got the meteorological seasons.
01:27They are defined by three-month periods to help with climate records and other things.
01:34And by that definition, meteorological spring begins on the 1st of March.
01:38That's this coming Sunday.
01:40But do either of these definitions make sense when you look at the data?
01:45That's what I'm going to be looking at right now.
01:48And to help me with that, I looked at some of our climate data.
01:52Specifically, the mean temperature across the UK for every day of the year.
01:57The mean temperature, that is the average of the maximum, the daily high, and the minimum, the overnight low.
02:03So, the mean temperature for every day of the year, falling through winter, rising through spring, and into summer.
02:14And you can see the mean temperature illustrated on this.
02:17This is the 1991 to 2020 mean temperature for the UK for every day.
02:23It's the black line here.
02:25And overlaid on top of the black line in the middle, we've got the daily highs and lows that we
02:31actually saw last year.
02:332025, the warmest year on record, of course, for the UK.
02:37So, I looked at the daily mean temperature.
02:40Not this 30-year period initially.
02:42I'll get on to why in a moment.
02:45I looked at the 1961 to 1990 30-year period.
02:49And I looked at when the warmest quarter of the year has occurred within that 30-year average.
02:58So, the warmest 91-day period.
03:02And came up with the result of the 12th of June to the 10th of September.
03:07In other words, if we just take the warmest quarter of the year and call that summer, then summer would
03:13begin on the 12th of June and it would end on the 10th of September.
03:16Equally, if you look at the coldest quarter of the year and call that winter, then by that definition, looking
03:23at the 1961 to 1990 30-year average, winter begins on the 6th of December and ends on the 6th
03:31of March.
03:32So, yeah, we know there's a lag effect in terms of the seasons.
03:35We know that summer doesn't necessarily start on the 1st of June and that there is a certain lag effect.
03:41But that lag effect doesn't last all the way to the summer solstice or, in the case of spring, the
03:47March equinox.
03:48But it's only a delay of a week or a bit longer.
03:52And actually, the definitions lie conveniently in the middle of the meteorological and the astronomical definitions.
03:59So, somewhere in between those definitions when you're looking at the warmest quarter and the coldest quarter.
04:04Now, of course, spring will lie in between the coldest quarter and the warmest quarter.
04:08And so, by that definition, spring begins on the 7th of March, end of next week, and then it ends
04:15on the 11th of June, which I think matches a lot of people's expectations or at least my expectations for
04:22that period of time.
04:24But what about more recent averages, the most recent 30-year average period?
04:29How does that compare?
04:30Well, again, looking at the warmest quarter and the coldest quarter, and the dates for the onset and the last
04:40day of each quarter are about the same.
04:43There's not much.
04:44There's one or two days difference in it.
04:46So, it's 14th of June to the 12th of September for the warmest quarter, and the coldest quarter is the
04:505th of December to the 5th of March.
04:52Very little in it.
04:53Very insignificant differences.
04:55So, essentially, the warmest period of the year and the coldest period of the year hasn't changed.
05:01But what has changed is the average temperature within those quarters.
05:05And for the warmest quarter of the year, 1991 to 2020, 30-year average period, it's gone up by about
05:140.8 or slightly more degrees Celsius compared with the 1961 to 1990 period.
05:21And roughly the same amount of warming as well for the coldest period, the winter quarter of the year.
05:28So, we've seen this average warming of each of those periods of time.
05:33But what if we were to apply the same temperature bounds from the 1961 to 1990 period to the more
05:45recent 30-year climate period?
05:47So, in other words, when we defined the warmest quarter of the year, that was roughly within a boundary of
05:5712.6 to 12.8 Celsius.
06:00But if you took those same temperatures that bookended the warmest quarter from the 60s, 70s, 80s, and applied them
06:08to the modern climate,
06:10actually what you find is that summer is around two days longer.
06:15That might not sound like much, particularly when you compare it with winter.
06:19Again, applying the same bookend temperatures from the older period to the more modern climate period,
06:26we find that winter now runs roughly 25th of December to the 22nd of February.
06:34In other words, it's about a month shorter.
06:36And a lot of that is taken away from December with another week or two taken away from February.
06:43So, why is winter so much shorter, but summer is only a couple of days longer?
06:49Well, the answer lies in the shape of the curve.
06:53If you look at the shape of the black line in the middle, it more or less plateaus during late
06:59December, over here,
07:01through January and the first part of February.
07:04And it plateaus at a temperature close to those bookend temperatures, 4 or 5 Celsius.
07:10Whereas summer is more of a rapid rise through spring and early summer and then a rapid drop late summer
07:18into autumn.
07:20It's more of a conical hill shape with these steep sides.
07:24So, if you increase the average temperature across the year,
07:29well, summer, you don't see much of a change in the onset or the end of summer
07:38because you've got the steep gradient either side of those.
07:41Whereas during the winter season, you've got many more days or even weeks where the temperature is close to those
07:48thresholds.
07:49And so, it's much easier for winter to push through those thresholds and rise above, significantly shortening the season.
07:56What happens with summer?
07:58It stays roughly the same length, but the peak temperatures in the middle get higher.
08:03In other words, winter gets shorter, summer about the same length, but hotter during that three-month period, more intense
08:14temperatures.
08:15And certainly what we saw last year, look at these spikes throughout summer, well above average.
08:21These temperature spikes occurring throughout June, July and August.
08:26So, those are the kinds of changes that the data suggests that we've seen during recent decades.
08:34And, you know, the kinds of temperatures that we would normally expect late autumn, early spring are now cropping up
08:41more regularly in the winter.
08:44And that's what we've seen this winter.
08:46Now, looking at this winter as a whole, we had a very mild start to December.
08:51First half of December, very mild.
08:53That's what this curve shows.
08:55Then it plunged into much colder than average for the start of the year, from around Christmas Eve onwards into
09:01the first half of January.
09:02After that, kind of been bobbing up and down, close to average, if not higher.
09:08And remember, this is the UK average temperature.
09:11It has been significantly colder across northeastern parts of the UK compared to elsewhere.
09:18Then, more recently, we've gone down a little.
09:21But in the last few days, we've risen significantly.
09:25And if you were to take the more modern thresholds or bookends for how winter is defined, and that's a
09:33temperature of roughly five degrees,
09:36then you can see we didn't go below five degrees, which is this line here until Christmas Eve.
09:42So you could say that autumn effectively extended up to the day before Christmas Eve.
09:48Then, we've consistently been around, at times below, but more recently, a little above average.
09:56And now we've risen significantly out of the coldest part of winter, perhaps.
10:03And so you may, and it may be too early to say, but you may say that this is a
10:08consistent warming that you'd expect at the start of spring.
10:12So, could it be that this winter has only lasted two months, from Christmas Eve up to around the 22nd
10:21of February?
10:22Well, that would certainly be an interesting one to look at.
10:27But, effectively, temperatures now have climbed significantly.
10:33And we are, over the next couple of days, heading towards the highest temperatures of the year and potentially the
10:40highest temperatures since early November.
10:43So, winter may be over, but is spring going to last all that long?
10:49Well, the peak of this warm spell is occurring during Tuesday and more essentially into Wednesday.
10:56Here's the bigger picture at the moment.
10:58We've got the jet stream coming in from the Atlantic, but then diving to the south, out to the west
11:04of the UK.
11:05And it's all getting bunched up out to the west of the UK because of this area of low pressure.
11:10This is the winter storm that northeastern parts of North America experience.
11:16Some really significant blizzards, snow drifts, crazy amounts of snow in parts of Boston, New York, and so on.
11:26That's now clearing.
11:27It's moving away, but what it's helping to do is inject extra energy into the jet stream and buckle the
11:33whole flow so that we've got this dip in the jet stream close to the Azores, out to the west
11:38of Portugal.
11:39That, then, forces the jet stream to rise to the north of the UK.
11:43And what we've got is this warm air, this subtropical air rising over all parts of the UK, all parts
11:51of the UK above average at the moment.
11:53But the highest temperature is expected to peak across the east and southeast into Wednesday.
11:59So, Wednesday, the peak of the warmth, before eventually this cold front that's out to the west pushes through.
12:08That clears through and it opens the door to another change on the way.
12:13A change which involves a flatter jet stream running across the Atlantic and pushing across northern parts of the UK,
12:21allowing these frontal systems to move through.
12:24And you can see there's a bit of a queue building up with these frontal systems.
12:28A couple go through on Thursday and Thursday night, clear on Friday.
12:32Then there are more weather systems to come heading into the weekend as that jet stream is back in charge.
12:39So, we're back to more typical weather for the time of year by the weekend.
12:44And by that I mean we've got low pressure between Scotland and Iceland.
12:48We've got weather fronts coming in from the Atlantic.
12:50We've got a relatively flat jet stream pushing these systems through.
12:53They're no longer getting stuck because of cold air and high pressure over Scandinavia.
12:58So, that's good.
12:59They are whizzing through, but there are plenty of them to move through.
13:04And they'll always dump the heaviest rain across western areas of the UK, especially northwestern areas of the UK.
13:11Northwest England, Western Scotland, Northern Ireland, North Wales seeing the heaviest rainfall over the next few days.
13:17I'll show you that in a moment with the rainfall maps.
13:20But you can see even into Sunday, first day of meteorological spring, even if we're already experiencing spring-like warmth.
13:28And we've still got these systems moving through the jet stream, still picking them up one after the other.
13:36So, very changeable weather to come.
13:39But for the next couple of days, at least, we've got plenty of sunshine for many, if not all, parts
13:44of the UK.
13:46This is the time of recording, 2 o'clock Tuesday.
13:49And you can see some reasonable sunny spells breaking out across England and Wales.
13:54Now, we've got a southerly breeze coming in.
13:57And we've got some convective clouds, some cumulus bubbling up.
14:01And there are some interesting things happening as the brisk wind from the south interacts with those cumulus clouds.
14:09And hopefully you'll be able to make this out on the smaller screen at home.
14:14But essentially, here we've got Wales.
14:16Here we've got Devon and Cornwall.
14:19We've got Kent here, East Anglia.
14:21So, this is a satellite image taken from lunchtime today.
14:26And what you can hopefully make out are these cloud streets across many central parts of England.
14:34So, these rows of cloud, otherwise known as horizontal convective rolls.
14:41That's what these are, these rolls of cloud.
14:43And what you'll note is that they are parallel with the wind, the wind coming in from the south.
14:48And these cloud streets are parallel with the wind.
14:54From the ground, some people might be able to see them in the sky, these rows of cumulus cloud.
15:00And what's effectively happening is if there was no wind, but still an inversion, so where the temperature rises with
15:08height,
15:08what you'd get is warm air rising from the land.
15:12And this is a spring-like satellite image, by the way, where you've got warm land heated by the sun,
15:19rising air and cumulus clouds forming.
15:21So, what we've got, warm air rising from the land, cumulus clouds forming, and then there's a cap because you've
15:28got that conversion.
15:29So, the rising air hits that and descends.
15:32Now, if there was no wind, or the wind was lighter, you'd have scattered clouds fairly disorganised all over the
15:38place.
15:39But what the wind helps to do is it helps to organise those rising and descending air currents into tubes.
15:47Because the wind is blowing along like that, the rising and falling air ends up moving around in a circle
15:54like that.
15:54And you get these tubes, and they end up with these cloud streets.
15:59Almost a very different thing is happening across parts of Wales into northern England.
16:03Here we've got the Lee effect of the mountains, and we've got more of a, what's the word, perpendicular rows
16:13of cloud with the wind.
16:15Because the wind's coming in from here, but then it's bumping over the hills.
16:18So, where it's forced up over the hills, you get rising air, you get an area of cloud.
16:24Then it descends on the other side of the hills, you get sinking air, you get a gap in the
16:27cloud.
16:28And then it continues to bounce, you get a bit of momentum.
16:31So, the wind continues to bounce, and wherever it's rising on the crest of that, you get a row of
16:36cloud.
16:36So, that's what you've got over Wales, these perpendicular rows of cloud.
16:41Anyway, we thought that was an interesting thing to share with you.
16:45But back to today's weather, plenty of sunshine across England and Wales, or at least this convective cloud.
16:51Cloudier towards Scotland and Northern Ireland, outbreaks of rain into northwest Scotland.
16:56These weather fronts are moving in, but they're stalling because of that extending jet stream, that extending upper trough.
17:03Brisk winds from the south, like I say.
17:05And temperatures peaking at 15 or 16 Celsius this afternoon across the east and southeast of England.
17:14Then, into Wednesday, a wetter day to come for Scotland, Northern Ireland, showery outbreaks of rain, some heavier bursts.
17:20The rain pushing into western England and Wales, breeze picking up, but plenty of sunshine remaining for the Midlands, east
17:28and southeast England.
17:30And this is the peak in the temperatures, chance of 17 or even 18 Celsius, making it the warmest spell
17:37of weather since early November.
17:40Then, by Thursday, the cold front's moving through, but then it stalls.
17:44Here we are.
17:45It's stalling across central and southwestern parts as another frontal system develops on the jet stream behind it.
17:53And really, we've got a wet spell of weather across many central and southern parts of the UK.
18:01Increasingly so late Thursday into early Friday.
18:04Showers following into Scotland and Northern Ireland.
18:07Either way, that mostly moves out of the way.
18:10By Friday, brighter skies follow.
18:13It's going to feel a little fresher as a result.
18:16Plenty of showers in Scotland, Northern Ireland, Northern England.
18:20Saturday, drier for a time, but the next frontal system comes along.
18:24That swings in from the west into Northern Ireland by mid-afternoon.
18:28Western Scotland, and then that moves across the country eventually.
18:33Although, a little bit of uncertainty about the timing of this system.
18:37Either way, it's going to bring some wet weather once again.
18:41So, how much rain are we going to see?
18:43And what are the kinds of contrasts from west to east?
18:46Well, this is a summary of the next few days.
18:4924-hour rain totals.
18:50Tuesday, very little rain.
18:52White areas for much of the UK.
18:53But we've got that wetter weather into the northwest of Scotland.
18:57Wednesday, wetter again for Western Scotland.
19:00But also for Northern Ireland, northwest England, parts of Wales, especially over the hills.
19:05Later, the southwest.
19:07And then into Thursday, you can see the emphasis for the rain shifts into western parts of England.
19:12And Wales, especially over higher parts, likewise into Friday.
19:17And running that through day by day.
19:21So, this is the rolling accumulations if we run through the next few days.
19:25By Wednesday, we're starting to see some really significant rain building up over western and northwest Scotland.
19:31This, of course, is part of the UK that didn't get much rain during the last six weeks or so.
19:36So, where southern parts of the UK, eastern and southeast Scotland, northeast England, saw a lot of rain.
19:44So, the distribution of the rainfall has shifted.
19:47It's more focused towards the northwest.
19:50North Wales, northwest England, you can see by Friday some brighter colours indicating some significant rain totals.
19:56Also, south Wales, parts of the southwest, Dartmoor, Exmoor, starting to see some significant rain accumulations.
20:03And, of course, these places have been wet recently.
20:05So, that's something we'll need to watch out for.
20:08But much less rain towards the east and the southeast of the UK.
20:12So, we've got this really stark west to east contrast.
20:18Also, a contrast as far as the temperatures are concerned.
20:22It's above average everywhere.
20:23But these are the maximum temperatures over the next few days.
20:26We're talking about nines to tens for the far north of Scotland, closer to 16 to 18 Celsius on Wednesday
20:32in the southeast and east.
20:35And then those temperatures slowly ebb away, but they're still above average later in the week.
20:39And we can see that by this summary here.
20:42Tuesday, Wednesday, the peak of the warmth, significantly above average temperatures.
20:48So, we're looking at temperatures 5 to 7 degrees above average in many places.
20:54More widely the case on Wednesday across East Anglia.
20:59So, that's the biggest difference compared with average.
21:01But the whole of the UK significantly above average.
21:04Into Thursday and Friday, the temperatures are starting to drop away.
21:10Still mostly above average, but the northwest has gotten perhaps a touch below.
21:15So, yeah, we're back to, by the weekend, westerlies bringing spells of rain and showers.
21:24Gusty winds at times as well.
21:26It's going to be breezy on Thursday nights.
21:28Coastal gales towards the southwest and then again later in the weekend perhaps.
21:32But nothing particularly exceptional for the time of year.
21:35And it's northwestern parts of the UK that will soak up a lot of the additional rainfall.
21:40Where we haven't seen that much rainfall recently.
21:44How long will that last?
21:45Well, there's a bit of uncertainty about this.
21:49Because as we go into spring, and this is the Monday the 2nd of March onwards on this graphic.
21:55This effectively shows the probability of different weather patterns into the next two weeks.
22:01You can see a lot of colours on the chart here.
22:05It doesn't necessarily mean that it's completely uncertain.
22:09A lot of this is down to the timings of different systems moving through or how the position of low
22:16pressure and high pressure in the vicinity of the UK are categorised.
22:19Because effectively it looks likely, if I click on a summary showing the top three most likely weather patterns into
22:31the middle of next week.
22:32It looks most likely that we're going to get a westerly airflow.
22:36What we call a positive North Atlantic oscillation.
22:39So that means we've got low pressure close to Iceland, high pressure close to the Azores.
22:43Similar to what we typically expect but a bit more enhanced.
22:47So an enhanced westerly airflow that would of course continue to bring above average temperatures, even if not as mild
22:54as it is today and tomorrow.
22:56It would continue to bring spells of rain and showers from the west, wettest over western hills.
23:01And these are the top three most likely weather patterns.
23:04Southwesterly here, the colours indicate above average temperatures.
23:09Westerly here and west to northwesterly here.
23:13So effectively it's variations on the theme.
23:17We've got high pressure over central Europe or over Iberia, occasionally bringing some drier weather into the south.
23:25But we've got low pressure over Iceland, occasionally bringing some wetter and windier weather in from the northwest.
23:31So first week of March looks like a continuation of what we've got at the weekend.
23:36This enhanced westerly airflow in the respect of temperatures, it may be spring like at times.
23:44But the unsettled weather, the wind and the rain might make it feel a bit more like autumn.
23:50However, as we've discovered, that's often what spring is like anyway at the first.
23:57First week of March, first week of meteorological spring.
24:01Well, it's often like this.
24:03It's often the case that March comes in like a lion and out like a lamb.
24:10So, yeah, might not be too long to wait for some more prolonged settled and dry weather.
24:16But nothing solid on the horizon as far as we can see at the moment.
24:21Thank you for joining me for this week's Met Office Deep Dive.
24:25Hope you enjoyed it.
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