Chat with the Chief – Severe weather on the way, what are the impacts 08/08/19 - video Dailymotion

Met Office

With further wet and unseasonably windy weather arriving on Friday and Saturday. Alex Deakin looks at the current weather warnings and talks with chief meteorologist Steve Ramsdale about the possible impacts and why the warnings are in force.

Transcript

00:00More severe weather is heading for the United Kingdom particularly on Friday

00:03and into the weekend. I'm going to be joined by Chief Meteorologist Steve

00:07Ramsdale in just a moment to talk about some of the potential impacts but let's

00:11just break down the warnings first of all deal with the rain initially the

00:15rain warning in force covering large parts of the UK during Friday but

00:19actually that rain is starting to come in during Thursday evening spreading in

00:24across the southwest. If we run through the sequence you can see this band of

00:28rain tracks northwards probably only lasting for an hour or so in some areas

00:32but look at the colors on there the bright colors showing some really

00:35intense rain as that band moves north and it's followed them by lots of

00:39showers and again some of those showers are likely to be very heavy indeed so

00:43some places are going to see quite a bit of rain during Friday. So that's the

00:47rainfall warning let's move on now and talk about the winds because actually the

00:50winds will start to pick up in the southwest later on on Friday but the

00:56wind warning really kicks in through Friday night and into Saturday as this

01:00area of low pressure moves northwards and the isobars start to squeeze

01:03together so the winds really picking up initially in the southwest but during

01:07Saturday strong winds likely across the bulk of England and Wales and then the

01:13next warning is for thunderstorms and that's in this zone close to the low

01:17pressure system where the winds are lighter and that's because that means

01:21the thunderstorms are likely to be slow moving so we have another warning for

01:25thunderstorms covering large swathes of northern Britain because as I say

01:30they'll be slow moving the thunderstorms here so they could drop a lot of rain

01:33just because of their slow moving nature meanwhile across the south we're going

01:37to see lots of blustery showers with the strength of the wind. So that's the

01:41warnings broken down let's talk a little bit more about the impacts let's bring

01:44Steve on thanks for joining me Steve you're a chief meteorologist one of

01:48you one of the parts of your job is to issue these warnings so let's talk about

01:53the rain warning first of all why do we have a rain warning in force for Friday

01:57across the UK? As we've seen we've got that band of rain pushing northwards and

02:01again followed by the showers on Friday and with those you could be seeing some

02:05quite large rainfall totals falling in quite a short period of time with the

02:08frontal rainfall itself we could be seeing sort of 10 to 15 mils quite

02:11widely falling along that band as it pushes northwards but the more

02:15concerning aspect is where we could see a 30 mils or so in only a few hours that

02:20kind of level of rainfall can often overwhelm just local drainage systems

02:24leading to you know ponding of water or even some localized flooding as well as

02:28well as that at least some spray and standing water just elsewhere so it

02:31means some difficult travel conditions but with that level of rainfall you

02:34could be seeing some localized flooding leading to disruption both on the roads

02:37but also to people's homes and businesses as well. So yeah as you

02:40mentioned there's some of the impacts that those those rainfall totals could

02:43bring there's gonna be a lot of surface water and spray on the roads and that's

02:45gonna have a big impact because it's Friday it's the middle of August there'll

02:48be a lot of people on the roads. That's right there's a lot of people traveling

02:51and you know well we we hope that summers are quite nice and dry and so

02:55when there's a lot of rain around sometimes it catches people out but with

02:58that as well again with it falling in such a short period of time that means

03:01conditions can change very quickly on the roads particularly when you're

03:04talking about showers which are a bit hit and miss in places so you could be

03:07that you're driving on quite a dry road you know quite happy really and then

03:10suddenly you're in a very heavy shower the roads suddenly becoming very wet

03:13your visibility is reduced it changes how you drive and it can lead to

03:17accidents and you know difficult driving conditions. Okay so that's the

03:20rainfall warning now the the wind warning across England and Wales as gusts

03:24picking up on Friday night but particularly during Saturday because a

03:27large chunk of England and Wales those winds are going to be unusually strong

03:31for the time of year. That's right and it's very important to say for the time

03:34of year as you do. We are looking at a potential for 40 to 50 mile an hour

03:38gusts inland by day particularly on Saturday but also very locally so 60

03:43miles an hour possible along coastlines as well. What that means is that you know

03:47during the winter we might not be worried about that people are used to

03:50that sort of level of wind during the winter is what kind of expect you know

03:53wet and windy weather. During the summer and believe it or not this is supposed

03:56to be peak summer this sort of level of wind people aren't necessarily prepared

04:00for. As you say there's a lot of people traveling but there's also children on

04:04holidays a lot of people traveling to different parts of the country a lot of

04:06people want to go on holiday there's caravans there's tents and things like

04:10that and they are susceptible to those strong winds. There's also a lot of

04:13outdoor events as well so there's a lot of outdoor and temporary structures

04:17being put up which are not necessarily able to withstand levels of wind at that

04:20level. One of the really important messages to get across is the impact so

04:23it's one of the things you deal with as a chief meteorologist because you issue

04:27these warnings based on impact so as you said in November December this kind of

04:31level of wind would not necessarily be causing the impacts that it's going to

04:35in August so that's one of the reasons why we have a warning in force. That's

04:38right yes it's all about what the impact on people could be as you say in November

04:42people we might have had a few events like this already people are used to

04:46them people are understanding they might put away the things that are going to

04:48blow around before that but during August when it hasn't been particularly

04:52windy recently suddenly getting something like this means people aren't

04:55prepared they're not prepared to change their you know way of driving way of

04:59preparing for things so it's important that we get that message out there to

05:02let people know it is going to be a pretty windy day. So it's a blustery day

05:05on Saturday in particular across England Wales just means the showers across

05:08England Wales move through quite quickly but the other aspect then those

05:11thunderstorms possibly across parts of Scotland Northern Ireland the winds

05:16there are that much lighter which means the storms are slow moving so they could

05:19drop a lot of rain. That's right and it's important there it's a bit hit and miss

05:23with thunderstorms where there's you know fairly slack flow it means that

05:26some areas will see very little rainfall you could get away with a dry day if

05:29you're lucky but where they do fall that means you could see some large amounts

05:33of rainfall falling in a short period of time and again like with the rainfall

05:37the day before where that does happen that means you could lead to some

05:40localized flooding and also difficult driving conditions again it's important

05:43people are aware that that potential for some heavy rain in a short period of

05:46time and quite locally is possible. Brilliant thanks for the summary of the

05:50warnings there Steve now let's take a look at the bigger picture let's people

05:53are asking why why is this happening so let's deal with the the bigger picture

05:58and maybe take a look at what's what's been developing out in the Atlantic over

06:02the past sort of 12 or so hours this is the satellite image so here's the UK

06:07here and it's this blob out in the Atlantic that's really been developing

06:10have we run through the sequence through last night just in here just talk us

06:13through that. That's right you can see the cloud before and you can see the way

06:16that this area of cloud is wrapping around and you get the sense that it's

06:20circulating around this area here and that's true that's what's happening

06:23that's where our low-pressure area is you've got this cloud being wrapped in

06:27through here now this sort of cloud signature we see on the satellite

06:30pictures with this type of low is often indicative of a low that's at it's

06:33almost as its lowest central pressure what we would call that is something

06:38going into its mature phase that means that it's not like to deepen anymore the

06:41winds around it are not likely to get any worse however that system itself

06:45will be coming northeastwards towards the UK so you can see the isobars around

06:49it representing those. Let's show that so here comes that low again and it's

06:53moving up towards the UK and if we just zoom in there the isobars squeezing

06:56together so really picking up across the southwest on Friday evening and then

07:00those tightly packed isobars throughout much of the day across the south on

07:04Saturday. Yeah that's right so with that level of wind strength across the UK

07:10you've got pretty strong winds throughout the atmosphere really and you

07:14can get those communicated down to the surface particularly around the showers

07:17what you often see in these sort of events is that the strongest winds are

07:21around the coast or up over hills that's partly because when they're coming in

07:25off the sea for example what we consider is the sea is a smoother surface there's

07:29less friction between the air and the surface whereas in land there's a bit

07:32more friction because what we call the roughness of the surface is a lot

07:36greater so you tend to get less strong winds in land however in this situation

07:40because there's potentially quite strong vertical motions associated with showers

07:44through the day that means some of that higher what we call momentum air or

07:47stronger winds can be pulled down from just above the surface to give you those

07:51strong gusts in land. So the potential for some the winds just suddenly whipping up

07:54all of a sudden. That's right it's going to be an appreciably windy day but

07:57particularly in and around showers that's where you could see some very

07:59strong winds for a shorter period of time but then back to sort of the

08:02standard windy day. Now speaking of standards we talked a little bit earlier

08:06about it I mean if you saw this weather chart in November or December you just

08:10think oh that's quite a deep low it just be a wet and windy weekend but this is

08:13unusual for this time of year. How rare is it to get these kind of gusts in

08:18August? Well we do often see one or two periods where we get the odd gust getting

08:23up to these sort of levels but mostly as I said before it's around coast or

08:27it's over high ground in land. So the idea of getting that to low levels and

08:31quite widely in land across the UK is quite unusual. You can see stronger winds

08:36in this if we go back to the 80s and early 90s there were periods where you

08:40could see 60 mile an hour winds quite widely in land. We're not expecting

08:43anything quite up to that level though there could be the odd 60 mile an hour

08:46gust through Saturday but it is still going to be unseasonably windy and again

08:51given the idea that there's a lot of people traveling there's a lot of

08:53events going on that's why considering the impact of this we feel it's

08:57necessary to have that warning out there. Brilliant fascinating stuff Steve thank

09:00you very much for joining me I know it's a very busy day. Please make sure you

09:04keep up to date with the very latest from the Met Office and the easiest way

09:08to do that is to follow us on social media.

Chat with the Chief – Severe weather on the way, what are the impacts 08/08/19

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