- 5 months ago
This is an in-depth Met Office UK Weather forecast for the next week and beyond. Thunderstorms are in the forecast this week but could we see a named summer storm next week? Bringing you this deep dive is Met Office meteorologist Honor Criswick.
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00:00Now at first glance you might think that the weather doesn't look that interesting this week.
00:06That's certainly what I thought after coming back off two weeks of leave.
00:09Just looks like typical British summertime but actually if you delve in a little bit deeper
00:15there are actually some interesting things potentially happening this week and as we head into next week.
00:21One of which is the potential for a named storm.
00:25Yes you heard me right we had storm Lillian last year quite late in the season so it's not uncommon
00:31to see kind of a named storm later as we head further into summer so we're going to take a look
00:37at the chances of that and also we could see potentially some quite hefty thunderstorms this
00:43week too so a couple of interesting things that we can sink our teeth into for this week's deep dive.
00:49So hello and welcome if you are new here make sure you give this video a like and make sure
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01:24every week welcome back and welcome to this week's deep dive so let's get into it shall we so yeah
01:31what's actually been happening with the weather over the last week or so and what's dominating the
01:37weather this week and mostly into next week as well well it's all thanks to this area of high pressure
01:42just situated to the southwest of the UK in the Atlantic and for those of you we might already know
01:49this is actually the Azores High it stretches up all the way from the Azores Island a big area of high
01:54and it's stretching its way just to the west of the country here now what we find is unfortunately
02:01because it kind of sits to the southwest through most of the week it doesn't actually bring anything
02:06super settled it does a little bit we've mostly got kind of typical British summertime weather as
02:12I've already said we've got some bright interludes some showers but we haven't got that high pressure
02:16sat over the UK bringing us kind of blue skies every day there are some caveats to the weather
02:22just to the north of this at times we get frontal systems swinging in in that northwesterly flow which
02:29we now have dominating the UK weather so if I just swing this forward as we head into tomorrow notice
02:36we can see that happening so here's the high and then we've got a frontal system just starting to edge
02:41into the west and with that northwesterly flow it's quite warm it's going to start to get quite humid
02:47wednesday and thursday so that brings us a risk of showers we're going to delve into that a little bit
02:52deeper in a moment because some of these showers could be quite heavy and possibly thundery and
02:56there's a little bit of uncertainty as to exactly where the showers are going to hit as is usually
03:01the way with a showery showery kind of setup but nevertheless with this frontal system more
03:06organized band of cloud possibly some light showery outbreaks of rain starting to push into the west
03:11later wednesday and into thursday and then eventually starting to creep in it's starting to fade it's
03:17quite a weak feature particularly as it starts to move its way in land so by early thursday morning
03:22yes there could be some more clouds and showers pushing into wales and parts of southwest england
03:27but as that system kind of fades away that's just indicating that it's a weakening feature but still
03:32the azores high sat to the west bringing in slight ridge of high pressure to the west of us
03:37and that pretty much sits there all the way as we head into the weekend but once again we can see by
03:44these pink colors these white arrows that's the jet stream a slight strengthening to the north
03:49of the azores high that creates low pressure to the north of this too so as we head later into the
03:55weekend after that ridge on saturday into sunday once again we see another system swing in towards
04:02the northwest so the first half of the weekend actually looks okay but by sunday we could start
04:07to see some cloud outbreaks of rain possibly some breezy weather too start to push into the northwest
04:13affecting scotland northern ireland possibly northern parts of england as well but the azores high is still
04:18remaining largely dominant across central and southern parts so probably the best of the weather here
04:24as we head into sunday i also just want to draw your attention to the jet stream because it does
04:30become quite significant when we chat about things later i've already hinted at the possibilities of
04:35a name storm and i just want to emphasize that that is a very low probability at this point probably
04:41around 10 chance but we are going to look at why but the jet stream here we can see
04:46is kind of situated just to the northwest of the uk this quite strong segment of the jet that means
04:54the azores high is allowed to build to the north of it don't forget the jet stream is kind of that
04:59that boundary between that cooler arctic air and then that milder warmer moist tropical air beneath it
05:06and what we do find sometimes is that areas of low pressure just to the east of the us or east of canada
05:12can sometimes be picked up by these areas of by the jet stream story by these areas of stronger
05:18stronger winds high up in the atmosphere and depending on the ingredients depending on where
05:24exactly those areas of low pressure sit they can be picked up by the jet stream and if they move over
05:28to the colder side of the jet so the northern side of the jet sometimes we can see cyclogenesis take
05:34place so rapid deepening but we need a few other ingredients as well to make that happen
05:40so there's the potential for a setup similar to this um to take place early into next week
05:46but we'll talk about that in a moment i'm going to make you wait for that one so let's focus on
05:51the weather this week to start off with so let's take a look at the details so i'm going to skip ahead
05:58to wednesday because by the time this video goes out tuesday's almost over so wednesday actually
06:03is going to be a fairly decent day for many of us we're not going to totally escape the showers
06:08you can almost actually at this point see three zones of weather so across north eastern england
06:14east anglia parts of central and southern parts of england you can see that cloud and that cloud at
06:19times is going to be thick enough to produce some showers they should be fairly isolated you're
06:24probably going to be quite unlike unlucky if you catch any of them and they should be rather light
06:29to moderate then if we move just to the west of this kind of zone of weather you can see almost
06:35clear skies so across uh parts of cornwall parts of devon parts of wales as well northwestern parts
06:41of england also through across central parts of scotland through into the scottish borders there's
06:46there's that kind of slightly drier wedge of air so by the time you reach tomorrow afternoon there's
06:51definitely going to be some sunshine around and then to the west of this once again as that system
06:56that i showed you earlier starts to push its way through some thicker cloud possibly producing some
07:01light outbreaks of rain across northern ireland some showers western parts of scotland as well
07:06could start to pick up those light outbreaks of rain so on wednesday there are going to be some
07:11brighter interludes some sunshine around perhaps a bit more cloud across eastern areas but as things
07:17start to warm up we're likely to see some breaks in that cloud as well so a bit of a mix of weather
07:22on wednesday but nevertheless it's not it's not going to be any uh heavy downpours or anything like
07:27that thursday however is going to be quite a different day for many of us so you can already
07:33see these brighter returns across the south here so yes heading into thursday there is a risk of
07:39showers some of these showers could be quite heavy possibly even turning quite thundery and you'll
07:44you can probably feel it in the air sometimes when things start to warm up it starts to turn quite
07:49humid it almost feels like a thunderstorm is on its way and for all you netheads there you'll know what
07:55the signs are you know what kind of clouds you'll be looking for the only thing about thursday is
08:00this model here this is our uh uk model that we use at the met office it's showing a lot of these
08:06showers quite spread across parts of the south some across east anglia eastern parts of scotland
08:12northeastern england and there's a little bit of model variability even at this lead time with the exact
08:18location of these showers i'll show you in a moment a lot of models are actually keeping these showers
08:22to the far east so still a little bit of uncertainty as to exactly where those
08:27heavier showers are going to be where those thunderstorms could possibly lurk so there is
08:32talk here at the met office potentially about some warnings it's unlikely today just because we're still
08:36a little uncertain as to exactly whereabouts they're going to be there's possibility that we
08:41could see a warning tomorrow keep an eye on our website across our social media channels for those but
08:46there's also a chance that actually the signal might take a bit of a downturn tomorrow and then we
08:51actually we don't see any warning so it's definitely a watch point uh the main watch point for this week
08:56is where those thundery showers are going to be and how intense they're going to be and if that's
09:00going to lead to warning but away from these kind of thundery showers northern ireland central parts
09:06of england parts of wales once again probably seeing quite a decent day on thursday so once that's
09:12once thursday's over there's still a chance heading into friday of some of those showers lingering on
09:17once again across the southeast there could be still some remnants of cloud but what we'll start
09:22to see on friday is a slight shift in our wind flow so rather than that more of a north west
09:27northwesterly flow we're starting to see a shift in our winds to more of a northerly and that starts to
09:32bring in some of that fresher cooler air as well so if you're not a fan of the humidity from the north
09:36on friday we'll start to see that fresher air that cooler air moving through the warm humid air
09:42probably lingering for a time across the south so still probably going to be quite warm and muggy
09:47there along with the uh along with the risk of those heavy showers still but otherwise friday
09:53once again there'll be plenty of dry weather around once those showers move through
09:56and for the weekend i know many of us are on the summer holidays but if you're unlucky like me
10:01you'll still be working and still looking forward to the weekend and saturday actually looks fairly
10:05decent for any weekend plans lots of dry weather once again as i showed you earlier that
10:10next system starting to push its way through into the northwest so more clouds some light outbreaks
10:15of rain moving through here the rain looks like it's probably going to stay to the far northwest
10:20for most of the day so it might just be that cloud starting to thicken up makes any sunshine
10:24more kind of hazy but for many of us it should remain dry particularly across england and wales
10:30and it's sunday where that system really does start to shove its way into the country so thicker
10:35cloud some outbreaks of rain and these potentially could be quite heavy as well so another watch
10:39point for the second half of the weekend um then i just want to talk a little bit around
10:46temperatures so let's take a look at what those are doing once again not super interesting
10:54temperatures are around about average for the time of year but it's certainly going to feel
10:58warm across the south and as i say wednesday and thursday temperatures not too different highs
11:04around 24 25 degrees particularly across uh southern and southeastern parts but as i say that
11:11that the humidity is starting to increase that warm muggy feel really starting to increase particularly
11:16on thursday and that could lead to those heavy showers so it's not going to feel particularly
11:21comfortable on thursday but as i say friday we can start to see even across central areas that
11:26fresher air coming through potentially still staying quite mild and muggy across the far south
11:31and then saturday likely feeling fresher for all but it's just not going to feel quite as muggy it's
11:36still going to be feeling warm in the sunshine on saturday with highs of 23 24 celsius even across the
11:41across the north with highs reaching high teens low 20s it's still gonna it's still gonna feel
11:46fairly nice so as i already mentioned at the beginning there's not loads going on but those
11:51thundery showers on thursday are certainly a watch point so let's investigate a bit more about
11:57those so on my left here we've got something i actually only discovered this morning is a thing
12:05um it's called a confetti plot which is really fun um and this is from mogreps on the left so showing
12:11the where members members of that model so model runs are showing uh kind of indicating where those
12:18possible showers could be so once again central southern parts but particularly around the london area
12:24parts of sussex kent across the southeast east anglia that's really where it's showing the bulk
12:29of those uh those showers with those more kind of red purpley colors but also once again eastern
12:34scotland northeastern parts of england there's also the potential for those showers there
12:39now here's an earlier model run from this morning across with our using our uk model that
12:44we use here at the met office and notice it's got a bit more it's actually showing um three hour
12:49accumulations of rain and it's showing it a bit more widespread across devon and cornwall exeter
12:55for example where met office hq is it's indicating some showers there whereas actually if we take a
13:00look at more grips it's not really got much of a signal across the southwest for any kind of intense
13:05showers the only um well it does kind of agree across eastern scotland northeastern parts of england
13:11that there'll be showers there so they agree the model's kind of agreeing there that northern areas
13:16could potentially see some of those showers but it's really showing a bit more of a broad area of
13:21those intense showers southern parts of wales as well as indicating could see some showers there
13:26so still a little bit of uncertainty there as to as to the exact location which as i said earlier
13:33is why we're not seeing a warning quite yet we just want a little bit of a more of agreement there
13:37with uh with model runs uh in order for a warning to be um issued and here we have once again the
13:45ukv model so the model that was just on my right there but these are earlier model runs so we've
13:50got the 3z run the 6z run and also the 9z run here on the far right and there's a slight indication if
13:57you kind of look at the detail earlier model runs really having that intense rainfall across central
14:03parts of wales central parts of england with earlier model runs it does start to push it southwards
14:09and then more recent model runs it's just starting to edge those intense rainfall totals across eastern
14:14areas so where we could see those intense showers so it looks like we're starting to see those models
14:19align a little bit more with uh model runs more recent model runs so a chance tomorrow we could
14:26see a bit more agreement and if the showers do still look like they could be this intense um then as i
14:31say there is the potential for a warning to be issued but of course we will update you if that does take
14:36place so thundery showers on thursday is definitely a watch point but otherwise the weather is it's fairly
14:44benign and there's not too much going on but obviously it's still going to be quite warm it's
14:51going to be quite humid and with that kind of weather we do tend to get a thundery downpours
14:55and it's not just in the uk it's also parts of europe that we've seen quite intense thundery showers
15:00and that does seem to be the case over the next few days and i just want to kind of take a little bit of
15:05a look at why that is as well so i've shown you already as we took a look at the synoptic pattern
15:12we've got the azores high really dominating the weather and just taking a look at some of the
15:17things i'm going to show you on the screen here and also things i've looked at earlier in the day
15:20it does look like that azores high is sticking with us it almost looks a bit like a blocking pattern
15:26it's not really changing and yet it's kind of creating quite changeable weather just because
15:32it does sit still to the west of us and that means those areas of low pressure can still swing in
15:38from the north or northwest and still can bring some changeable weather into the northwest so that's
15:45when we start to see troughs moving through areas of low pressure so some showery rain like what we
15:50could see on sunday but then ridges of high pressure build and it turns dry and bright and then once
15:55again another trough moves through so that's why i'm starting to hate that word changeable but that
15:59really is the best way to describe it um ridges of high pressure troughs so showers dry showers dry
16:06and that's all because of this area of high pressure just sat to the west of us this is
16:10pressure and normally so the pressure difference compared to normal and these darker pink colors
16:15showing that pressure is higher than normal across western areas that's just kind of showing almost
16:19looks like a pink egg just showing where that azores high is going to be sitting
16:24and where this azores high starts to build that's normally where we find the jet stream just to the
16:32north of this that high pressure builds to the south of it and to the north of it that's where
16:36low pressure systems move through and with this kind of set up those low pressure systems will be
16:42swung in by the jet stream and where that jet stream dips where we can see that boundary between
16:47the warm and cold air we can kind of see that um that lower pressure difference here just to the east
16:53so that's where it's kind of swing down any low pressure systems and because of this we do tend
17:00to get low pressure systems moving into northern northeastern parts of europe that's the kind of
17:05setup we've seen over the last week or so and here we have temperatures so because those low pressure
17:11systems more cloud we don't see that intense heat building quite as much so we've actually had this is
17:17temperature normally once again so temperatures compared to normal for this time of year
17:21we've actually had fairly cool temperatures across northern and eastern parts of europe and it's all
17:27because of that dip in the jet stream where that high pressure is blocked creating that dip creating
17:32low pressure systems to move through we've had some quite intense thunderstorms here so some quite gusty
17:37winds frequent lightning some large hail in these kind of areas and still over the next couple of days
17:43northern parts of italy parts of germany still at risk of seeing those quite intense thunderstorms but
17:47obviously further east across turkey across greece we've had above average temperatures really hot dry
17:54conditions creating those quite devastating wildfires wildfires so there really is that contrast across
18:00europe at the moment with temperatures actually above average across the uk so with that pressure
18:06building across the uk bringing in those low pressure systems dropping those temperatures we can
18:12still get quite intense thunderstorms because the land across europe is still quite warm that allows
18:19the air to rise it condenses creates clouds creates those cumulonimbus clouds when that heat is
18:24intense and creates those thunderstorms and as a result of this here's our precipitation
18:31abnormally so precipitation compared to normal where that zoars high has sat it's been drier than normal
18:37where those low pressure areas have moved through it's been wetter than normal across many areas of
18:42europe so northern northern and eastern parts of europe once again germany italy many areas seeing actually
18:50um and some quite intense precipitation so more than you'd usually see at this time of year
18:56so thunderstorms are actually impacting not just the uk but other areas of europe as well so i think it's
19:02just quite interesting seeing those different kind of weather patterns and how it all links together
19:07um and creates quite a contrast across um across parts of europe now what about looking further ahead
19:14well it still as i say looks like we're going to be dominated by that azores high just sitting to the west
19:20of the country we might have to zoom in here it's a little bit small but we've got um
19:25pressure anomaly to the top here in the middle um we've got temperature anomalies and just to the
19:32just on the bottom row here we've got precipitation anomalies so this first column here is this week
19:39up until the third of august and the following week and then the third week so we can see that azores
19:44high it's still dominating but what it does it slowly doesn't become quite as intense and it's slowly
19:50shifting its way eastwards as well so that once again is pushing any low pressure systems that drop
19:56down um to the east of it once again those will be pushing eastwards as well and that has an add-on
20:01effect to the kind of weather we'll see so taking a look at temperatures those cooler temperatures
20:06across northern and eastern parts of europe eventually obviously still being two to three weeks
20:12away this could change obviously we know that already but this uh the bigger pattern is indicating
20:17that as that pressure system shifts eastwards we'll start to see things warming up in two to three
20:23weeks across parts of europe and we won't see those below average temperatures here and along with that
20:30kind of shift eastwards we'll start to see that kind of change in the precipitation anomaly as well so
20:36things starting to become drier than average so we'll start to see less of those intense thunderstorms
20:41across the uk and likely across northern and eastern parts of europe as well now if the azores
20:47high does kind of sit in this this kind of location it might start to get a bit of obviously high
20:53pressure moving around in a clockwise direction might start to get more of a northeasterly perhaps
20:58south the southeasterly flow of air and if we do start to see things warming up across europe
21:03there's the potential for that warm air to then start to be dragged towards us here in the uk
21:09after having a look at temperatures um earlier in the day it doesn't look like we're set for any kind
21:15of intense heat waves but there is some signal that temperatures will start to warm up uh in the next
21:20couple of weeks or so and this is probably linked to this kind of change in setup with that pressure
21:25moving eastwards and potentially a change of our wind direction and picking up those warmer temperatures
21:29off europe but still a few weeks away still a lot to play for uh so at this moment in time it really
21:34is too soon to send as it stands temperatures still across the uk are sticking around average
21:40if not a little bit warmer across the south so it's really interesting i think to see how the kind
21:46of jet stream can link to um can link to the weather here and it's all to do with pressure uh
21:52precipitation temperatures and it's all linked together not just um here in the uk but across
21:58europe as well not only this but we do start to see a link in our weather at times across parts of
22:05the us and i'm sure if you are um a keen watcher of us here during the deep dives i'm sure we've
22:12spoken before about named storms storm stormy areas or areas of low pressure being dragged up
22:18close to the us being picked up by our jet stream and moving towards us here in the uk and there is a
22:24signal that potentially as we head into next week this um this could happen again once again i'm
22:30going to stress it's probably around a 10 chance that we see an actual named storm with uh with areas
22:38of low pressure and for cyclogenesis to take place so you need all the ingredients to really come together
22:43at the exact right time particularly at this time of the year but as i said we had storm lillian
22:48around this time last year i think it was august yeah it was august last year
22:52um so we can get storms kind of at this point in summer but it's not totally common it can happen
22:59however and there are some model runs indicating that if all those ingredients come together at the
23:05right time there is the potential for perhaps a storm it may not even elevate into a storm it could
23:12just be strong winds it could just be a frontal system moving through there might not be enough power
23:16there to kind of generate a full actual low pressure system and and thus turning it into a storm
23:23i'm going to try and explain briefly why there is a chance so it's really the european model actually
23:29has shown over the last few days an area of low pressure starting to move in to the northwest of the
23:35uk this is the this is the uk just here here's the azores high here and as we move further west this is just the us
23:43and moving into parts of canada here's iceland here sorry it's a bit you might have to tilt your head to
23:48the left here i probably should have rotated that a little bit sorry but hopefully you can just about
23:52navigate whereabouts we are and what we have um close to the coast of the us we just have these
23:59slight areas of low pressure here um indicated just off the coast and don't forget the jet stream is
24:05that boundary between that cooler air and that warm tropical air and what we find as we head further into
24:10the future so this is for midnight on saturday and moving forward into midday sunday now here's that
24:17area of low pressure just being picked up on the kind of left side of that jet on the cooler side of
24:23the jet just being picked up by a jet stream and then hence moving forward towards the uk so if we
24:30have this take place so we'd need that warm tropical air to the south we'd need that area of low pressure
24:37to be picked up on the left jet exit that's where we undergo some potentially some quite deep
24:42rappening some cyclogenesis and we also need kind of a trough feature to the north so they're the three
24:47main ingredients that we would need for this to take place and as the jet stream moves this area of
24:52low pressure towards the uk if it spins up enough press the right button then we could start to see this
25:00area of low pressure just to the northwest of the uk so that'll bring in cloud heavy outbreaks of rain
25:06and notice there's quite a few isobars on this chart as well so some strong wins too but we need
25:11all those ingredients to come together in order for this to take place and actually there's a few model
25:17members and recent model runs as well of the european model showing this the global model that we use at
25:22the met office not so much there are some members indicating it but the majority of members really are
25:29showing that actually it's probably just going to be high pressure still that azores high just to the west
25:34creating those changeable conditions particularly in the northwest of the country and it doesn't
25:39necessarily mean that we'll either have a low pressure system or nothing at all it could just
25:43bring in some strong winds it could just bring in some outbreaks of rain towards the northwest
25:47as i said earlier probably around a 10 chance of a named storm but impactful winds probably a bit
25:53higher around 30 chance so it's definitely a watch point as we head into next week but still a few more
26:01model runs to take a look at before we get to that point and still need a little bit more agreement
26:05within those model runs and different through different models as well in order to um really
26:10predict what's going to happen there but definitely something worth uh worth keeping an eye on for next
26:15week but this week it really is those thunderstorms that we need to keep an eye on
26:20so what else did i want to talk about yes thunderstorms as you know if you're if you're a fan here i do
26:27sometimes like to go into a little bit of my background as a forecaster and go into a little
26:32bit of theory and i am a big fan of teffigrams i wasn't when i first saw them when i first started
26:37learning about them in university i think they look quite intense when you first look at them there's
26:42lots of lines and lots of different things going on but actually as forecasters they really are so
26:47great and once you kind of get to grips with them and understand them you do learn to love them and i
26:52just thought i'd go through a little bit of theory obviously we talk about models and model runs all the
26:56time but what would happen if everything shut down we didn't have any models we didn't have any internet
27:02what would we actually do how would we be able to forecast the weather how did they do it back in
27:07the day well teffigans are a really good tool in order to do that so this is one taken for kind of
27:13thursday late afternoon in the london area and if you're not familiar with these this solid blue line
27:22as we move our way up the graph this is going high up into the atmosphere this solid blue line is the
27:28temperature of the atmosphere as we go higher and in order to determine temperature we'd have to follow
27:33these faded green lines down and here's temperature along the bottom axis here
27:38so if i wanted the temperature here i'd follow it down oh i keep doing that i'd follow it down and i'd
27:46read off the temperature here so this is this solid blue line is temperature as we go up in the
27:51atmosphere we've got this dashed blue line and that's our dew point temperature as we go up into
27:56the atmosphere so the temperature the air would have to cool to in order to become saturated and water
28:02vapor um to um to be created so essentially the closer these lines are together the moister the air is
28:11and the further apart they are the drier the air is and what we can do is we can calculate from um
28:17from using these lines these temperatures as we go up into the atmosphere we can calculate what cloud
28:23we're going to get how thick the cloud's going to be is that cloud going to produce any showers is it
28:28going to produce any hail or is it going to produce any lightning so what i did before i pop this on the
28:33screen i created what we call a norman's point construction so this is following these lines here and this
28:39here where there's the little blue x hopefully you can see might need to zoom in again um this is what
28:46is called our lifting condensation level so essentially when we start to reach that point
28:51that's roughly whereabouts our cloud base is going to be and this is calculated through maximum
28:55temperature of the day so i've gone for 26 degrees on thursday in the london area so before this point
29:02as we follow this diagonal line as the air is rising it's following a dry adiabatic lapse rate the
29:07air is still quite dry but once we reach this point the air is now saturated so we follow this
29:13curved line a saturated adiabatic lapse rate it's called stay with me i promise this will hopefully
29:19make sense in a minute but what this shows us is this gray shaded area and that is the convective
29:25available potential energy cape for sure and this actually is indicating so here's the base of our cloud
29:32here's roughly the top of our cloud so we can see this cloud is pretty deep it's roughly the base
29:37around 5000 foot the top of the clouds probably around 30 000 foot if we follow this axis along
29:43here's um here's the heart kind of height of the atmosphere as we go up so that is a really thick
29:49cloud instantly when you'd look at this you'd think accumulonimbus cloud and this shaded area is
29:55telling us basically the potential of how convective that cloud could be so if it's going to be a convective
30:00cloud accumulonimbus cloud we're looking at showers we're looking at the possibility of hail and thunder
30:06so instantly as a forecaster you'd be looking at this and this is what we call skinny cape
30:10so there is enough energy here to create a shower now already we've looked at the setup we know
30:17showers are on the cards there's a risk of showers but we want to know how intense those showers are
30:21going to be and if we have a risk of thunderstorms and this is something i actually learned through here
30:27in the met office college this is one of our empirical techniques that we might be able to use
30:32usually here in exeter if you are forecasting particularly on the aviation bait on the aviation
30:38bench sorry you're looking after quite a few airports so you don't always have time to use
30:43techniques like this but if you're just forecasting for one airport or a defense base for example
30:48you might want to use this just to kind of look at how intense your showers could possibly be so i've
30:53already drawn on these red lines here so as i said this is the base of the cloud along the x-axis
30:58and then the top of the cloud along the y-axis so around 5000 feet and then the top of our cloud
31:04was around 30 000 feet and this is indicating a heavy shower which we already guessed anyway
31:10so a heavy shower is definitely on the cards just by taking a look at that tephogram and there's a few
31:16rules here indicating how intense that rain is going to be how what your visibility could potentially look
31:22like with regards to how intense that shower could be and depending on the type of cloud it is so if
31:29it's a cumulus cloud a cumulonimbus cloud a towering cue for example that's more of our convective cloud
31:36so that changes how intense the precipitation could be compared to more dynamic clouds that's more of
31:41your frontal cloud moving through so there's lots of different rules i won't go through them all
31:45but a good one is is that if the depth of the cloud is more than 10 000 feet you've got around
31:5090 percent of showers this is taken for the london area so across the southeast so we've got a good
31:5590 chance of showers already just by looking at that tephogram another thing we can look at here's a
32:02tephogram once again on our smaller scale so this was the this was our solid blue line on the last one
32:08this black one here and this is our salr saturated adiabatic lapse rate and remember we were looking at
32:15that kind of gray shaded area and in order for hail um in order if we're looking at that tephogram and
32:21we're thinking about hail there needs to be about a four degree separation or more in between the
32:28temperature of our environment and also that salr that curved line in that shaded area and if we go
32:34back to our tephogram we can kind of see there's roughly about four degrees there it's probably about
32:40three to four degrees separation there so already we're in or thinking that there is the possibility
32:46of hail there and in order to determine the kind of risk of thunder here at the met office if you're
32:54if you're forecasting through civil aviation you tend to really rely on model runs to see the kind of
33:01risk of thunder but already we know we've got a cumulonimbus cloud we know we've got a risk of
33:05hail we know we've got a heavy shower coming so you can probably guess there's a good chance of
33:09thunderstorms here as well and we have a few different instability indices that we could use
33:15there's a good four or five here that we could use for example ratcliffe is quite a popular one
33:20so we would take a look at our potential temperature at a thousand hectopascals so what the temperature
33:26would be if that parcel of air was brought down to the ground with no moisture or no heat added
33:31was just moved down adiabatically so we want the temperature there and then we take off the
33:36temperature around about 500 hectopascals i hope this is making sense it sounds very complicated as
33:41i'm saying it and here this kind of indices shows that if that number if we take away those numbers
33:47it's around 29 to 30 that means that there's thunder probable and i did already calculate this because
33:53it was a little bit complicated to do and i think the number there we go nice and big the number was about
33:5930.8 and this is indicating thunder probable about 29 to 30 so there's definitely a chance
34:05of thunderstorms looking at the teferground we've got all the ingredients there but as we've already
34:10noted looking at the um the kind of different models it's just whereabouts those thunderstorms
34:17are going to be so that's where the uncertainty lies we know we've got the ingredients for a thunderstorm
34:22to be created it's just whereabouts that location is going to be i really hope that made sense
34:30um yeah i think it's sometimes quite interesting to look at because obviously we talk about models
34:35a lot we talk about the the differences in the model runs and between the different models that
34:39we use here at the metoff but sometimes i think it's nice to kind of go back to the basics
34:44and really take a look at what we use here if we didn't have any models at all what we could
34:49actually look at to see if thunderstorms were on the card so i hope that made sense but if not please
34:54do leave some questions in the comments section and we can maybe take a look at it on the live on
34:59friday so i think that was pretty much everything i wanted to talk about so i hope you have enjoyed
35:05this week's deep dive i've not done it in a while so i've kind of forgotten how exactly to explain certain
35:12things but i think that all hopefully that all made sense and i think it's really interesting to
35:16take a look at how everything links together how the jet stream can potentially pull in some weather
35:21systems all the way from the us how the position of the jet can impact whether here in the uk and
35:26towards europe and how that change in jet stream creates a change of where that high pressure can
35:30sit and thus having an effect on weather further ahead so i hope you did enjoy it i hope it made sense
35:37and yes please do leave any comments or questions in the comment section below but otherwise i hope you
35:43have enjoyed make sure you have clicked subscribe make sure to give this video a like and of course
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35:53there as well then you won't miss our faces and if you want more information on the weather further
36:00ahead particularly the chances of thunderstorms on thursday or the chance of that low pressure system
36:05moving through next week well we've got alex burkehill tomorrow on the 10 day trend here on youtube as
36:12well and hopefully by tomorrow we'll have a bit more information with regards to potential warnings
36:16for this week or the kind of what whether we could be looking at next week as well so don't forget to
36:21take a look at that one tomorrow as well but otherwise that is it from me so i'll catch you again very soon
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