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Storm and Convective Discussion 10th June Onwards


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Some decent CAPE being shown across the eastern side of the country for tomorrow afternoon/evening, which if tapped into could bring some isolated but fairly intense thunderstorms. However, as some have pointed out, we have high pressure sat over the top of us acting like a lid on convection. GFS and WRF still break out storms over the Humber through the late afternoon which transfer southwards with time through Lincolnshire and eventually into East Anglia by late evening and the SE overnight. However, the higher resolution Euro4 model does not show any precipitation breaking out up to its last frame at 6pm tomorrow. The met office pressure charts do show a trough feature heading south tomorrow late, this could be a trigger, along with wind convergence all the way down the East coast into EA.

 

At present I am unconvinced of anything happening tomorrow as I think the cap may hold firm. However, with a lot of sunshine expected and temperatures possibly topping 26c there is a possibility and it'll be worth keeping an eye on subsequent charts and then, perhaps more importantly, surface obs on the day.

Edited by Supacell
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If the cap is broken then the energy build up under the initial cap would be unleashed and likely be explosive especially under the forecast temperatures. The trough feature is interesting I did not realise a trough could be present under hp. I think we definitely need something special to get these storms going. Unfortunately I have only come across this in my experience once (very recently) to see a high pressure setup. It wasn't successful but I would not be disappointed if one did become successful though :)

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 Quote Speedway Slider:

Now, does that mean that anyone under the length of that bolt, ie from where it left the anvil/cloud to the point if strike, lets say 7 miles away would here the thunder instantly as it would be directly over people for 7 miles, everyone underneath the bolt would not count past 1 second before they heard the thunder produced from the section of bolt above them, if so, that would be the thunderclap from hell, yes?

 

No, remember the bolt is quite a couple of thousand feet above their heads, so ther is a certain time delay. Those bolts do sound rather ominous though, reverberating thunder with deep bass. The thunder at the point where the bolt then strikes the ground is instant and incredibly loud, more like an explosion at the ammo dump :bomb: Never heard something like that before or since

 

On the video Norfolk Sheep posted the stepped leaders are clearly visible btw

 

Ralph

 

Edit: explosion is putting it mildly, massive detonation is the better word, remember that a pos strike carries a multiple of amperage as compared to a neg CG, the diameter of the ionised channel is thus larger and more air is displaced at once!

Edited by Generalelectrix
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 Quote Speedway Slider:

Now, does that mean that anyone under the length of that bolt, ie from where it left the anvil/cloud to the point if strike, lets say 7 miles away would here the thunder instantly as it would be directly over people for 7 miles, everyone underneath the bolt would not count past 1 second before they heard the thunder produced from the section of bolt above them, if so, that would be the thunderclap from hell, yes?

 

No, remember the bolt is quite a couple of thousand feet above their heads, so ther is a certain time delay. Those bolts do sound rather ominous though, reverberating thunder with deep bass. The thunder at the point where the bolt then strikes the ground is instant and incredibly loud, more like an explosion at the ammo dump :bomb: Never heard something like that before or since

 

On the video Norfolk Sheep posted the stepped leaders are clearly visible btw

 

Ralph

Ah, ok, don't think I explained what I was getting at, let me try again....

In a normal storm situation, if it's say 4 miles away and produces a standard -CG then you could count to say 16 seconds before hearing that bolts thunder, yes?

If that storm then chucks one of the +CG that travels 8 miles across before heading down so the ground strike is next to you, you would hear instant thunder, yes? Ok, if you are half way so 4 miles from its cloud and 4 miles from its strike point and the bolt has passed directly overhead, yes? Then the bolt superheats it's channel all the along, won't the section of the strike above you  create thunder as well, so the 4 second per mile rule doesn't apply as every mile from the anvil/ cloud has some explosive air from the section of the bolt above.... Yes? 

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@ Speedway: Umm, sort of see what you are getting at, in the case of the bolt passing overhead at 4miles up and striking ground 4 miles away the rule would apply, otherwise, if the bolt passes overhead closer and strikes 4 miles away the rule wont apply, you get to hear thunder first from that section of lightning closest to you, regardless of where it finally hits ground. Thats why these strikes have such a long, reverberating thunder. 

 

Ralph

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http://onenameglobal.com/lightning-in-super-slow-motion-is-stunning/

 

Just seen this posted on FB from the 9th June in the Netherlands   :)

 

Amazing that why is there saying lighten never follows same path clear when slowed lightening often repeats one case horizontal one went the exact same path.  Wish we could tap into free energy.

 

Been some amazing days meteox has friday east coast another possible good day.

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Gfs 06z looking good for midlands and east tomorrow!!cape values slightly higher on this run aswell with temps of between 23-26 degrees!!humidity looks very high tomorrow!!

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Gfs 06z looking good for midlands and east tomorrow!!cape values slightly higher on this run aswell with temps of between 23-26 degrees!!humidity looks very high tomorrow!!

 

 

so much for high pressure and I don't think temps will be as high as that maybe further south but not here

Edited by Gordon Webb
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A few in here really need to read this thread http://forum.netweather.tv/topic/77200-a-guide-to-thunderstorms-in-the-british-isles/ CAPE is not the be all and end all for thunderstorms and without any forcing to trigger development it really does remain 'potential'.

 

Quite...it is important to note however that pressure throughout tomorrow will be falling away and there will be a pronounced CZ right down the entire eastern portion of the UK. Windfields also showing up a very curious pattern in the form of a surface low type feature over London/Kent region (perhaps one of the bizarrest and most pronounced I've seen!). Irritatingly this does not overlap the highest CAPE so what would come of it, if anything, is up for debate.

 

 

 

Posted Image

 

Posted Image

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Does the length of the lightning bolt effect the length of the thunderclap?

I suppose that's difficult to calculate because of the succession of secondary rumbles....

 

Primary factors are, I would say;

 

1. Proximity of the lightning to the receiver 

2. Power of the lightning (voltage/amps) and whether the bolt is positively or negatively charged (notwithstanding proximity, positive are normally FAR more powerful and the thunder reflecting that)

3. Air temperature (not just a ground level but at different altitudes)

4. Humidity (not just a ground level but at different altitudes)

5. Windspeed and direction (not just a ground level but at different altitudes)

6. Background noise (i.e traffic, wind, rain, aeroplanes (unlikely), etc)

7. Topography - Thunder sounds very different on the coast (more like the gradual and smooth roar of a jet in my experience) compared to inland (more thumpy and intermittent) where it rebounds of hills, trees, buildings, etc

 

When you say 'length' do you mean duration or length from end to end?

Edited by Harry
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Things really could go bang. I remember a few setups like these in the past too. 

East Midlands into Lincolnshire looking like the hot spots. Definitely a trigger there in the form of a convergence zone down the Eastern side of the Country. Seems to have upgraded slightly too. Who'd have picked this one out lol!

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A good bit of Surface based CAPE on offer throughout tomorrow, the front moving down from the NW could provide some surprises with a trigger along with the already mentioned convergence zone running down the country. Who thought high pressure was boring! :)

 

post-9615-0-88777600-1402591121_thumb.pnpost-9615-0-07394100-1402591128_thumb.pn

 

 

Central & eastern areas favoured looking at the convective ppn charts.  

 

post-9615-0-09323800-1402591351_thumb.pn

Edited by Liam J
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Our post processing spits out dilute CAPE, and has values of ~700 max (generally 400-500J/kg) in south, central and isol northern UK later tomorrow afternoon, so not directly comparable, but perhaps not as severe as the graphic above posted by Liam. I'd say though there is a great degree of interest (and has been since Monday) in the destabilising effects the over-running trough will have for profiles in south and central UK tomorrow evening. Maybe even Wales with orog uplift late afternoon...As the upper short-wave trundles through cold advection could erode warm noses from the 15C theta-w plume below, with isol thunderstorms popping up into the late evening. So CBs not ruled out tomorrow!(also mid-level instability can result in Ac castellanus => lightning! though don't get your hopes up too much as detail is not pinned down and won't be until short lead time)

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Although not as high as the SB instability some moderate ML CAPE on offer around 700-1100 j/kg. I'm taking all of this data from the hi res NMM-6, so it's a a bit one sided as I haven't looked at the other models! But at this short range I tend to stick with the the NMM-6 :D Quite surprised when I saw the potential this evening! 

Edited by Liam J
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Although not as high as the SB instability some moderate ML CAPE on offer around 700-1100 j/kg. I'm taking all of this data from the hi res NMM-6, so it's a a bit one sided as I haven't looked at the other models! But at this short range I tend to stick with the the NMM-6 :D Quite surprised when I saw the potential this evening! 

Yup, could get some moderate values, though not comparable to the storms earlier in the week though! I'm looking at UKPP, which is post processed data to match location better from UKV at this lead time.

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Yup, could get some moderate values, though not comparable to the storms earlier in the week though! I'm looking at UKPP, which is post processed data to match location better from UKV at this lead time.

I guess it's a case of wait and see! So the UKPP is showing lower values of instability when compared the NMM-6 charts I've posted? Are you able to post any of the UKPP charts by any chance....Be interesting to see for comparison, what grid resolution is the UKPP running at, UKV 1.5km? :)

Edited by Liam J
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I guess it's a case of wait and see! So the UKPP is showing lower values of instability when compared the NMM-6 charts I've posted? Are you able to post any of the UKPP charts by any chance....Be interesting to see for comparison, what grid resolution is the UKPP running at, 1.5km? :)

 

As I alluded before it's hard to compare as it outputs dilute CAPE, which is cloud base to cloud top. It's actually scaled to 2km, for rather boring and fiddley reasons. Unfortunately probably cannot post charts, so I won't haha. But interesting to see 3hr ppn output (18z-21z) as well from UKV (have not looked at anything else that's in public domain, maybe other output agrees?) with lincolnshire looking most at risk and isol SE/London by 2100z tomorrow. Considering no dynamic activity tomorrow, these can be assumed convective so further support potential for some storms about!

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What is going on tomorrow? I see the local forecast saying just a few showers, i look at the charts and there showing lots of cape and a convergence zone right over me. The met office precip looks quite good too. Sorry to be ignorant but is there something I'm missing?

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