10 Day Trend – Warming up but for how long will the sun shine? 18/09/19
The rest of this week will see temperatures rising and plenty of blue sky once some morning fog has cleared. A big change is on the way with next week having a very different look and feel. Alex Deakin takes us through these changes.
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00:00Welcome to the Met Office 10-day
00:02trend, where we take a look at the
00:03bigger picture and some of the
00:05flavours affecting our weather into
00:07next week.
00:08It's fair to say the next week will
00:09taste very different to this
00:11week. If you're enjoying the
00:13sunshine, we'll make the most of the
00:14next few days, because for many,
00:16the sun will last through the rest
00:18of this working week and into the
00:19first part of the weekend.
00:21And the days will be getting
00:23warmer as well.
00:24But we are going to see a little bit
00:25more mist and fog around in the
00:27mornings, particularly Thursday and
00:29Friday morning.
00:30After that, we will see the change.
00:32Now, there's a bit of uncertainty
00:34about exactly when we'll see the
00:35change, but basically by next
00:37week, expect much
00:39cooler weather, cloudier weather.
00:41And with some places hardly seeing a
00:43cloud this week, that won't be too
00:44hard. And yes, after
00:46a pretty long dry spell for some, we
00:48will finally start to see a bit more
00:50rain coming in.
00:52Let's take a look at the bigger
00:53picture. We can see why the weather
00:54has been so fine and settled this
00:56week. The jet stream is driving to
00:58the south, way out
01:00in the Atlantic, then to the north.
01:02And this ridge
01:04is allowing the surface high
01:06pressure to dominate.
01:07It's been sitting across the country
01:08for a number of days and will
01:10continue to sit across us through
01:12Thursday and Friday.
01:15Now, as the nights are getting
01:16longer and temperatures drop
01:18off at night, it will turn cool
01:20enough for some mist and fog patches
01:22to form, particularly close to the
01:23centre of the high where the winds
01:25are light. So expect some mist and
01:26fog, as I say, on Thursday and
01:28particularly Friday morning.
01:30But the high is gradually
01:32ambling away.
01:33It's very slowly
01:35just drifting to the east and that
01:37is allowing southerly winds to pick
01:39up and they will waft up some
01:41warmer air by the time we get to
01:43Friday and Saturday.
01:44So in the sunshine, it'll feel quite
01:46a bit warmer by the time we get to
01:47Saturday. How much warmer?
01:49Well, temperatures like last weekend
01:51could be back into the mid-20s
01:52across parts of the south,
01:55depending exactly on the wind
01:56direction, because if it's coming in
01:58from the North Sea, parts of the East
01:59Coast could be a little cool and
02:01it perhaps won't be quite as warm in
02:03the West because here we're
02:05starting to see a change on
02:06Saturday. There'll be more cloud
02:07rounds and that's because a weather
02:09front is approaching.
02:11Now, there's a bit of uncertainty
02:12about the exact timing of this
02:14weather front.
02:15That's because it's a blocking
02:17area of high pressure that we've had
02:18in control.
02:19And when that breaks down to
02:21low pressure and weather fronts,
02:23there's always a bit of uncertainty
02:24about exactly how that happens.
02:26The computer models struggle a
02:27little bit with that changeover.
02:29So as I say, the timings of this
02:31weather front open to a bit of
02:32uncertainty.
02:33But what this weather front will do
02:34is bring more cloud into the West
02:36and eventually some showery rain.
02:38Actually, it's developing into an
02:39area of low pressure, which will
02:41throw rain across many areas by the
02:43end of Sunday.
02:43And this cold front sweeps away
02:45that warmer air, so it will be
02:47turning cooler and fresher.
02:48And with isobars pinching closer
02:50together, it will also turn quite
02:52blustery. So a very different feel
02:54by the end of Sunday.
02:55That transition happening this
02:57weekend, the sunshine or
02:59maybe still to start for many on
03:01Saturday when it could be pretty
03:02warm, but it will be turning wetter
03:04and cooler during
03:06the weekend.
03:07Now, I said there's a fair bit of
03:08uncertainty about the track and
03:10position of that weather front as
03:12it moves across the country on
03:13Sunday. Why so?
03:14Well, there's a number of factors
03:15going on. If you look at the bigger
03:17picture again for the early part of
03:18next week, you can see it's
03:20pretty confused as areas of low
03:21pressure, in particular, the jet
03:23stream is no longer in a
03:25straightforward pattern.
03:26It's trying to cut off here and
03:28there's another stream of it there
03:30across the near continent.
03:31And it's also developing out
03:33in the Atlantic. So it's a bit of a
03:34messy scenario with what's going on
03:35high up in the atmosphere.
03:37There's also events going on across
03:39Greenland that are affecting things.
03:40And also this area of low pressure
03:43is adding an extra complication
03:45because of where it's come from.
03:46Now, by the time we get to Monday,
03:48it looks like this will be bringing
03:49in weather fronts and isobars.
03:51So we'll see a spell of wet and
03:53windy weather. But there's a lot of
03:54uncertainty about the timing of
03:56this weather system as well,
03:57because if we
03:59track it back over
04:01the previous few days, coming
04:03back to the current position of
04:04that low pressure system, and we
04:06actually discover that low is
04:08currently a hurricane
04:10affecting Bermuda over the next
04:1224 hours or so.
04:14Now, it's a hurricane, lots of
04:15isobars on the chart there,
04:17very strong winds, and it's been
04:18driven by the warm waters over
04:21the tropics.
04:22As it moves further north, well,
04:23it will change.
04:25It won't be a hurricane anymore.
04:27In fact, by Friday, it's just an
04:28area of low pressure.
04:29Certainly by the time it approaches
04:30the UK, it's just a standard
04:32area of low pressure.
04:33But it is set to bring
04:35a spell of wet and windy weather.
04:36Notice how it's lost that warmth,
04:38that energy.
04:40And it could be affected
04:42by the jet stream.
04:43And that's why there's uncertainty.
04:45This low pressure will bring energy
04:46and that really confuses
04:48the atmosphere a little bit.
04:50And so there's always more
04:51uncertainty when you draw up
04:53one of these old tropical systems
04:54close to the country.
04:56But it may well get affected by the
04:57jet stream because the jet
04:59stream has changed position by
05:01early next week.
05:02And that's the big change for next
05:03week. Compare and contrast the jet
05:05stream this week.
05:06We saw it earlier up across
05:08Iceland and down to the east
05:10of the UK, allowing that high
05:11pressure to sit across us.
05:12Next week, the low the low
05:14pressures are being driven by the
05:15jet stream, which is much further
05:17south.
05:18So with the jet stream in this
05:19position, our weather patterns will
05:21be very different.
05:22It means we'll see low pressure
05:24systems moving pretty much directly
05:25across the country.
05:27Now, this is next week.
05:28The exact position of these lows,
05:31how much rain they bring, how
05:32strong the winds are, open to
05:34a lot of doubt at this stage.
05:36But the main themes, a big change
05:38on the way, a big change to much
05:40more changeable weather.
05:41We're not going to see endless days
05:43of sunshine. There will be spells of
05:45rain, but it probably won't rain all
05:46week. There'll be some drier and
05:48brighter spells in between.
05:49Very typical autumn fare,
05:51you may say.
05:52Now, for the very latest details day
05:54on day, always follow the Met
05:56office on social media.