- 3 months ago
This is an in-depth Met Office UK Weather forecast for the next week and beyond.
Warnings are in place for some wet and windy weather. But what is different about this low?
Bringing you this deep dive is Met Office meteorologist Honor Criswick.
Warnings are in place for some wet and windy weather. But what is different about this low?
Bringing you this deep dive is Met Office meteorologist Honor Criswick.
Category
🗞
NewsTranscript
00:00Hello and welcome to this week's Deep Dive and of course the weather this week has started
00:05to turn quite interesting. That's if you compare it to last week but we did have high pressure
00:10but we were stuck under the anti-cyclonic gloom. It was dry, settled but there was plenty
00:15of cloud around. This week however is totally different and it's all because of this low
00:21pressure. Often at times this week it is going to bring in some very wet and windy weather
00:26particularly later Wednesday through into Thursday and if you're keen-eyed or if you've
00:31followed us on social media channels you'll have seen already this morning we have issued a couple
00:36of wind warnings and also a rain warning. So let's take a look at the details. So to start off let's
00:43take a look at our winds. We follow this along here. So I'm going to just move this over to
00:52midday on Wednesday or actually Wednesday afternoon sorry where actually we can see winds are mostly
00:58light. We're not expecting any gusts at this point above 50 miles per hour and actually Wednesday is
01:03probably going to be quite a nice day. It'll be dry, bright, sunny, some showers in places but actually
01:08overall a half decent day and it's really later into the day as we start to see that area of low
01:14pressure which I just had to which I just had on the screen. It will start to skirt its way across
01:19the south and as it does so we'll start to see an increase in winds and we'll see an increase in
01:25gusts too. So you can already see the main areas that our model is pointing out. So western coast
01:30of Wales, parts of the southwest, possibly parts of the south and also the southeast but note that
01:36wind direction. It is a more northerly wind direction so actually a lot of the gusts across parts
01:41of the south are going to be offshore and as this system drifts its way eastwards a chance we could
01:47see wind speeds particularly around exposed coasts around 50 to 60 miles per hour which is why we do
01:54have a couple of wind warnings in force. I'll get on to those in a moment but really with that
01:58northerly wind it's going to be across any northerly exposed windward coasts that we're going to see a
02:03strengthening of those winds possibly parts of the southwest as well and the low pressure system
02:09will eventually continue to drift its way eastwards through into Thursday and with a change in location
02:15of that low then we start to see the strongest of the winds become more confined to eastern areas.
02:20Now once again the strongest of those gusts are likely to be offshore but really any exposed coasts
02:25particularly exposed to that northerly wind direction could possibly see some quite strong
02:31gusts in the range of around 50 to 60 miles per hour. The low pressure system will continue to push
02:38its way eastwards but it actually becomes a feature that kind of lingers for a time into the North Sea and
02:43with that we continue to see that northerly wind direction and you can still see here even though once again
02:50most of the strongest winds are going to be offshore any exposed coast once again are going to be catching
02:55those gusts and even inland areas even though they're not showing the pink modelled colours here even inland
03:01areas are still going to be quite breezy quite gusty at times on Wednesday and Thursday but even as we head closer
03:07into the weekend it's still going to be a breezier feel and also notice once again that wind direction
03:12really coming from the north and that's going to have a knock-on effect in terms of our wind chill
03:17temperatures but we'll come more into that in a moment. So wind speeds are going to start to increase
03:22later Wednesday through into Thursday not only that but we're going to see a fair amount of rain
03:26rain associated with this feature as well. So if I go into later tomorrow this is six hour rainfall totals
03:34our models are really starting to show now where the where the possible most impacted areas are going
03:40to be so you can see as we head kind of later through into Thursday that it's really that south
03:47eastern half of the country there so central parts of England parts of Lincolnshire East Anglia even
03:52parts of the south and southwest are really going to start to see those rainfall totals tot up. So we
03:58can see here widely between sort of 20 to 30 millimetres of rain but once again it's going to be those
04:04hilly areas those more exposed areas where we're going to catch possibly some quite persistent heavier
04:09downpours. Most areas are going to see around about an inch of rain and as that system continues to drift
04:16its way eastwards obviously we'll start to see the more persistent outbreaks of rain become a bit more
04:20confined to the east as well. Well we could still see those totals tot up through into Thursday and
04:26through into the early hours of Friday until that low really starts to clear away. So it's going to be
04:32windy it's going to be wet initially through the early hours of Wednesday it'll be quite wet particularly
04:37across the south and then as that system drifts to the east things will start to ease away but we do
04:42have some weather warnings in force and it's of course all our warnings are based on impact so there
04:50is a chance particularly across parts of the southeast where we could see some windy and wet conditions
04:55obviously a highly populated area there's a chance we could see some impacts in association with this
04:59feature. Now obviously they're not super clear on this so I'm going to try and draw around them just to
05:05make them that little bit easier to clear but there is a warning mostly across eastern areas so parts of
05:11Lincolnshire, East Anglia, southeast England and also the London area so this is going to be a wind
05:17warning I'll just wait for that to catch up and we've also got a second wind warning around western
05:23coast so western coasts of Wales also western and northern coasts of Devon and Cornwall so this is where
05:30we've got the the wind warnings there so the initial one across Wales parts of southwest England that's
05:36going to be valid from 4am on Wednesday all the way through until 6pm the same day and this secondary
05:42wind warning across eastern areas that's going to be from 9am all the way through up till midnight so
05:47wind speeds mainly in the west around 40 to 45 miles per hour quite widely even inland areas could see
05:54these kind of wind speeds but around those coasts they could potentially get up to around 50 to 60 miles per
05:59hour now across eastern areas obviously I showed you that low drifting eastwards those winds those
06:05northerly winds really starting to pick up as it does so so wind speeds could be slightly higher here
06:10once again 45 to 55 miles per hour possibly 65 just pushing into the mid 60s miles per hour just as that
06:18system drifts across but that once again going to be around those exposed coastal areas and we're going
06:23to go through in a moment a little bit of model uncertainty some models do have that low slightly deeper the
06:29deeper the low the stronger the winds and if this takes place we could potentially be looking at
06:33wind speeds around 65 to 75 miles per hour so obviously a chance that it could create some impacts
06:40we also have this rain warning issued here this is across much of the south and southeastern kind of
06:46swathe of the uk so once again this is where we're expecting possible impacts as a result of persistent rain
06:52um so once again um around 20 to 30 millimeters but where we do see those heavier persistent downpours
06:59a chance we could see between 30 to 50 millimeters of rain so that's why these warnings have been issued
07:06and like i say quite a populated area so a chance we could see some localized flooding not only this but
07:12quite strong winds at this time of year obviously the trees are still quite in full leaf and with a more
07:16northerly direction those trees are a little bit more exposed obviously leaves on railways that means
07:22the lots of delays or cancellations uh in terms of trains it can create slippery surfaces and obviously
07:29we're looking at some localized flooding too so do keep an eye on our website for any warning updates
07:35in terms of wind and rain over the next couple of days so obviously i've already discussed why we are
07:43starting to see this change it's all thanks to low pressure even this afternoon we've still got low
07:47pressure situated to the northwest that's bringing in plenty of showers across western areas but it's
07:52this area of low pressure that we're keeping an eye on this is the one associated with the warnings
07:58this is the area of low pressure that will eventually drift its way across the atlantic
08:03and at times it does get picked up by the jet stream now of course we have spoken before about
08:09areas of low pressure getting picked up by the jet stream they undergo rapid deepening when they fall
08:14into what we call the left jet exit the colder side of the jet and this can sometimes undergo quite
08:21rapid deepening we can sometimes get quite rapid cyclogenesis as a result of this now that's not
08:27what quite what happens with this area of low pressure and i'm going to try and explain why
08:32so here it is wednesday off uh tuesday afternoon if we move through into wednesday it starts to get picked
08:37up by that jet stream and it moves quite quickly closer towards parts of the southwest now this is
08:43the main jet core and what you'll notice is that it's actually situated slightly further south than
08:49we'd initially expect not only this but you've got this secondary jet streak which is really pushing
08:54in from the north pushing its way downwards and pushing that low across i'm going to show you that in
09:00a slightly different way this is something which i took from our chief this morning so there's that main
09:06jet core that we were looking at the low situated around about there and here's that secondary streak
09:13of the jet stream just pushing its way southwards not only this but you've also got some areas of
09:18stronger winds just to the north of this main core you've got one pushing into parts of the southwest
09:23so it's actually a really complicated picture high up in the atmosphere and that's one of the reasons
09:30why we have had some model uncertainty the models all slightly um modeling the jet stream slightly
09:36differently and obviously that has a knock-on effect as to the track the timing of the low how deep that
09:42lower and that area of low pressure is going to be so that does explain i think some people mentioned
09:47it yesterday you know why is there still this uncertainty at such a short lead time and this is
09:51one of the main reasons why the jet stream the fast flowing ribbon of air high up at the atmosphere
09:57it's not always set that it just moves from west to east sometimes we get quite complicated setups
10:02and this in turn does create that uncertainty so let's head back to our area of low pressure and
10:09what you'll notice is just jump back it does start to sit where we would usually undergo some quite rapid
10:18deepening but this load doesn't really start to deepen until actually later thursday when it starts to
10:24push away from the jet stream and starts to push into the north sea so i'm going to attempt to explain
10:31why um so here we go let's just drag this back just have to stand in front of the screen for one moment
10:40so here it's not far from the left jet exit but it would probably need to be slightly shifted further south
10:46and because it's just slightly shifted further north and that this jet stream here is slightly further south
10:52than usual and it stays in that location and we almost see that load detaching from that jet just
10:58a little bit as it starts to push into parts of the southeast then it's not until it moves off until
11:05it undergoes a little bit more deepening than what it does so as it moves in so i just want to head back
11:10and explain why we tend to look at the left jet exit well i'm going to attempt so because it's a little
11:17bit complicated but i'm going to try and simplify it a little bit and i'm just going to move over to this
11:22side of the screen so let's say this is our jet stream
11:30here we go and i've drawn it on slightly curved make sure i'm still in the picture i've drawn it
11:35on slightly curved just to kind of show that as that air is moving into the jet stream it's a little
11:40slower and when we get towards the jet core this is the center of the jet those wind speeds really
11:46start to pick up this is where we tend to see the strongest wind speeds and then we start to see
11:51slight spreading out of our jet the wind speeds start to decelerate decelerate they start to slow
11:57down as they move out of that jet stream core so here is really where we start to see the strongest
12:03of the winds so if this is our wind speeds moving into that jet stream represented by this arrow
12:12starts to accelerate as it does so but we also have another force at play here and this is called
12:19ageistrophic motion now ageistrophic motion is essentially a wind that's it's kind of out of
12:28balance between the coriolis force and the pressure gradient force i'm not going to go into what those
12:32are now we've talked about it loads of times in different videos but essentially it's the
12:37difference in the balance between those two forces so if you imagine if you imagine a car driving around
12:44a banner bend at a constant speed it either starts to accelerate or slow down and then suddenly you have
12:50an unbalance of those forces that's a very simplified way of explaining what ageistrophic motion is
12:57but in terms of this context what you really need to know is that ageistrophic motion will always move
13:01to the left of acceleration so where we see our winds accelerate our ageistrophic motion will always
13:07drift to the left so within our jet stream core if our forces are being pushed to the left the air is
13:14being pushed to the left so this is where we start to see with all the air pushing northwards we start to
13:20see more air here and it starts to sink we start to get convergence aloft according to dynes model so
13:26convergence aloft is when the wind speeds push together and push down so convergence aloft is here
13:33and because our air is moving northwards we've got less air now to the south and with less air air
13:39starts to rise so this is where we have an area of divergence so convergence the air is moving down
13:45the pressure is increasing where we have divergence the air is moving up and the pressure is decreasing
13:51but obviously we usually talk about the left jet exit that's where we tend to pick up areas of low
13:58pressure where we tend to see rapid deepening so as the air accelerates into the jet stream we've got
14:05we start to see the fastest wind speeds here and as it starts to move out of that jet core our wind
14:11speeds start to slow down and this means in terms of forces our acceleration is actually moving this way
14:19so this is where our wind speeds start to speed up we start to slow down so the force of acceleration
14:25moves this way and then our pressure gradient force if we remember moves to the left so once again that
14:31air is being pushed to the south more air being pushed to the south it's moving downwards convergence aloft
14:37so we have our area of convergence here so where the air is moving away from the north that's where
14:43we're we're needing to find more air to replace that air that's moving away so it's starting to
14:49find it lower down so it's we start to see that air begin to rise and then we get divergence aloft
14:56and it's here where we have divergence where we get a development area and this is why we tend to look
15:03at the left jet exit if areas of low pressure are being picked up by the jet stream not only this but this
15:08towards the north of the jet that's our cold side of the jet as well so another trigger really acting
15:14to create that divergence aloft to really lower that pressure even more as that small scale low starts
15:21to drift its way across the atlantic and really acts to fuel it as it drifts its way across and moves
15:26towards us in the uk so a very simplified example and diagram please do take a look at some of our other
15:33videos if you want a little bit information on that but this is essentially why we tend to look
15:38at the left jet exit so let's take a look at our area of low pressure once again because like i said
15:46initially it starts to drift across this this is the jet stream i just attempted to draw here
15:53starts to move into the left jet exit but as we get later into wednesday through into thursday
16:01it becomes detached nevertheless though it's still a relatively deep area of low pressure you can see
16:06plenty of isobars on the chart which is why we are starting to see that increase in winds not only
16:11this but it's bringing in plenty of rainfall as well as usual low pressure systems do but it's one of the
16:17reasons why at this moment in time it is not a named feature i'm going to come on to that a bit more in a
16:25moment later that's the reason why we're not naming it but there's potentially other countries that might name
16:30this system more on that in a moment but anyway it's still bringing in some wet and windy weather
16:37but it's not going to be quite as intense the wind speeds aren't going to be quite as strong it's not
16:41a named feature because it starts to move away from that jet stream it has less of a trigger in order to
16:46deepen but it does start to deepen as we drift into thursday we don't really say goodbye to that low
16:54really even until the weekend it sits there swirling around into the north sea as i showed you on the
17:00wind gusts earlier with that northerly flow it's still bringing in some quite gusty conditions
17:05across eastern areas of the uk and it kind of sits there it does start to drift its way
17:11eastwards a little bit starting to move its way away from denmark but then we've got high pressure
17:16starting to build out to the west which i'm sure will eventually push it out the way
17:20but on thursday it still tends to bring some quite intense winds across the south so what's another
17:28what's another trigger if it's not going to be the jet stream what's another trigger creating this
17:32in order to intensify well that's all thanks to something called positive vorticity advection
17:41oh i've lost you they switched off it's got very technical today i've not got many deep dives left so i
17:47thought i'd take my advantage of getting all technical with you guys but it's positive
17:52vorticity advection and all because we've got a deep upper trough starting to build into the north
17:57sea so rather than the jet stream being the trigger for this area of low pressure it's actually that
18:02deep the deep upper trough building in eastern areas so we can see this positive vorticity this is
18:09where the area of low pressure sits just out to the west into the north sea we can see it shown by
18:14these red and these blue colors so all along here is thursday this is at 6z 12z and then 18z so all
18:20through thursday here we are and we can even see it as i say it's kind of lingering around out to the
18:25west we can still see that area of low pressure sticking there all the way through into kind of
18:30saturday really so why is it the upper trough that's starting to create that um that intensification of
18:39the low we'll start to see that pressure start to drop once again obviously the lower the pressure
18:45the deeper the the deeper the low the deeper the storm sorry and the stronger the winds those eastern
18:51coast still picking up those strong gusty winds and it's all because of this upper trough and that's
18:56because just to the east of troughs or to the right of troughs however you look at it we start to get
19:02divergence once again so we start to get um divergence happening uh aloft so therefore we've
19:09got that wind um we've got the air parcel sorry starting to rise we've got convergence to the west
19:16of the trough we've got divergence to the east so similar setup to the jet stream where we have those
19:22convergence areas and those divergence areas but where we see the divergence areas is to the east of
19:27the trough and that's where the area of low pressure starts to sit so we've got air rising once again
19:32really intensifying that low and dropping the pressure at the surface so this area of low pressure
19:38is an interesting one because it's kind of starts to slack as it drifts across the south then as it
19:45pushes into the north sea that's when it starts to intensify and it's also one of the reasons why
19:51we're not naming the storm obviously we're also in partnership with um with meteren and we're also
19:58in partnership with um uh km kmni the the danish met services and we're really part of the kind of
20:07northern european group who tends to name these storms so if someone else decides to name it for
20:13example france meteor france because they are going to see some quite strong winds associated with this
20:17feature particularly across their northwestern coasts then actually it won't be
20:21bram it will be benjamin um so there could potentially still be a named storm but it's
20:27unlikely to be named by us and really because this system is drifting across the south it is
20:32impacting a few different countries not with strong winds but it's also bringing in some quite
20:37intense areas of rainfall so northern parts of europe are very unsettled at the moment intense rain we've
20:42also got some quite intense thunderstorms i think it was yesterday there was a tornado recorded
20:47in france we've also seen winds so intense that they've knocked cranes over so they've already had
20:54quite a lot of unsettled weather and as this area of low pressure starts to build through we're going
20:58to see further spells of um of wet and windy weather so it could potentially be quite an impactful low
21:04and obviously when we have impactful areas of low pressure they do tend to get named or where we see
21:10um kind of warnings build up from yellows to ambers we start to think about naming
21:15so a chance that a different country could name the system but as it stands tuesday afternoon i'm
21:21probably jinxing myself and it's being named right now but the met office are very unlikely to name
21:26this storm now obviously if this area of low pressure does then become more intense and some
21:31slightly different models start to look like they're more aligning in this area of low pressure
21:36is going to be slightly deeper then we would obviously look at escalating the warnings and then
21:40we would look at naming but that's very very unlikely the more likely um thing that might happen is
21:46that another country may name this system but we'll we'll take a look at that over the next uh of over
21:52the next 24 hours and so and see what happens but at the moment it is not a named feature
21:58so obviously this system then starts to drift its way over to the southeast or over to the east sorry
22:06and then what starts to happen let's switch some of these off we do start to see a rebuild of high
22:14pressure once again out to the west it's not got a h on it just yet not h for high pressure not for
22:19honor but it is high pressure as we know because that will move around in a clockwise direction
22:24well we've got high pressure building in the west and obviously moving in that clockwise direction we've
22:32got low pressure out to the east moving in the anti-clockwise direction so then of course we start
22:38to get that northerly flow of air so over the weekend things are going to start to feel that bit
22:43chillier let's take a look at those temperatures i'll go a little bit further in time let's go from
22:50thursday onwards because of oh actually let's go from wednesday so temperatures at the moment i mean
22:55they're not that exciting they're either a roundabout average or in some places they're a touch above some
23:00places they're a touch below particularly in the north but sometimes it's not always the value of
23:05how what the temperature actually is it's how it feels because obviously last week it didn't
23:09it felt kind of nice in the sunshine but under all the cloud it felt quite cool but i always think this
23:14feels quite differently as those winds start to intensify and it's really that wind chill that starts
23:18to and starts to bite a little bit the temperatures at the moment like i say around average around
23:24average so around 14 15 might get to kind of 16 degrees celsius into tomorrow wednesday actually
23:30looks like quite a nice day but notice those temperatures starting to drop away as we head
23:36through into the weekend actually looking more like the high single figures possibly 10 11 degrees
23:43but actually it's those wind chill temperatures that are really gonna you're really gonna start to
23:48feel it so if we take over to saturday even though temperatures like i just said 10 11 degrees when you
23:54add on that chilly northerly flow particularly across parts of scotland i mean aberdeen wind chill
23:59temperature is looking about three degrees so it's going to be feeling much colder as we head towards
24:04the weekend if you're not a fan of the cold weather well actually it's going to be just a very small blip
24:10of chilly weather and there's that high pressure starts to build or begin to see a bit more of a
24:13westerly flow and more rain probably particularly across the northwest some brighter interludes and ridges
24:19it'll be one of those changeable weeks once again as we head into next week so it's a
24:23brief colder spell and things will probably get that bit milder but along with the milder weather
24:28it'll probably be wet that's all i'm going to say because obviously it's alex burke hill on the
24:3210-day trend tomorrow so i don't want to step on his toes so for a bit more information on the
24:36weather ahead do check that out tomorrow afternoon with uh with alex b but just a heads up for the
24:43weekend it is going to start to turn chilly so obviously quite unsettled this week some rain warnings
24:48in force some wind warnings in force things will start to settle down over the weekend there could be some
24:52showers even some wintry showers across scotland as things start to turn a bit chillier wintry showers
24:58mainly across mountainous areas there's not going to be as much snow as perhaps some media outlets
25:03we'll try and let you believe um but yes a change is on its way a brief colder blip before that high
25:09pressure starts to build in perhaps bringing some slightly nicer conditions next week obviously it's
25:13the start of half term for many i know half term i don't have children so i have no idea but i know
25:18half term has started this week for some so it's not been the best start but particularly this weekend
25:23it will be a start half term for many of us in the country and you might be out i don't know pumpkin
25:28picking or something getting ready for halloween so there's going to be lots of nice weather but
25:32definitely wrap up warm because uh it is definitely going to be on the chilly side and still quite windy
25:37as well so if you've decided to stick up your halloween decorations make sure you've tied them down
25:41um so i think that's pretty much everything no there was one more thing that i wanted to talk about
25:49because quite a few of us quite like our space weather don't we actually if you take a look at
25:54our tick tock any moment now by the time this uh video is issued there will be a tick tock from alex b
26:01once again about the orionid meteor shower which has actually it's already started i wrote down the dates
26:07because i knew i'd forgot i'd forget but it's between oh no it's starting from now 22nd of october
26:14until the 7th of november so there'll still be a chance to see it but tonight it's really going
26:19to be its peak and it's quite good weather conditions if you want to go take a look as well
26:23i believe the peak is from around midnight oh i'm on the wrong day i was going to say that looks a lot
26:28cloudier than i thought here we go so the peak is going to be from around midnight until 6am and you can see
26:35if we take a look at our what the um clouds being modeled out you can see there's quite a lot of
26:40clear skies and eastern areas in particular are going to see quite a few of those clear skies are
26:44still going to be a little bit breezy i will admit particularly across scotland around those coastal
26:48areas still quite breezy there we can see most of us are going to see clear skies and even this cloud in
26:53the west it's probably patchy low cloud so there'll be some breaks at times possibly some mist and fog as
26:59winds are fairly light in most places so there might be some mist and fog in places but particularly
27:04particularly between midnight and six let's drag that round there are going to be plenty of clear
27:11skies so if you're a big fan of uh meteor showers it's definitely worth going to have a look because
27:16i think we had uh it was a uh last week we had the um the supermoon and quite a few people saw that but
27:23we also had the aurora because the supermoon was so bright uh not many people could actually see the
27:27northern lights across parts of scotland so if you missed that and we're a bit gutted or there might be
27:32something else that you can spot tonight so yes i'm glad i remembered that one of course if you get
27:36any cool pictures definitely sent them into the net office maybe we can feature them on this week's
27:41live which of course is on friday 12 15 like it is every week and this week it's me and alex burkhill
27:48and it's actually the last time i'm going to be on the screen answering questions so if you have any
27:54questions for me specifically make sure to tune in um this friday and it's also going to be the last quiz
28:00that alex burk will be um will be able to give me so fingers crossed for a five out of five but yes
28:05if you do have any questions or comments particularly about anything that i've gone through this afternoon
28:10make sure to leave them in the comments box and i'll take a look at them and try and answer some of
28:14them during the live and of course if you're new here make sure to subscribe if you liked this video
28:21do please give it a thumbs up i've not got many of these deep dives left we've got a double whammy of
28:26deep dives on me i'm afraid i'm also going to be on the one next week so if you have any questions
28:30maybe i can take a look at them too if i don't get the chance to answer them on friday but otherwise i
28:36hope you enjoyed as i say if you want a bit more in-depth weather on the on the next 10 days or so
28:41you can take a look at alex burkhill's video on youtube later otherwise that's everything from me
28:47so i hope you have a lovely week and i'll catch you again very soon
Be the first to comment