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Convective / Storm Discussion Thread - 31st May 2017 onwards


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Posted
  • Location: Benfleet, South Essex
  • Weather Preferences: Sunny and breezy with a bit of cloud, about 20C
  • Location: Benfleet, South Essex

Sorry if this seems like a silly question, but what's the difference between ML CAPE and MU CAPE?

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Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield

Well going through the GFS good mid level cape and surface based cape and no cap so in theory should go bang.

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Posted
  • Location: Cambourne Cambridge 70M ASL
  • Weather Preferences: Blizzards,Hot Thundery nights.
  • Location: Cambourne Cambridge 70M ASL
11 minutes ago, Supacell said:

Thank you, what a great site, even has animation!

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Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
6 minutes ago, Jcweather said:

Sorry if this seems like a silly question, but what's the difference between ML CAPE and MU CAPE?

This may help you https://stormtrack.org/community/threads/sb-cape-vs-ml-cape.28402/

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Posted
  • Location: Cleeve, North Somerset
  • Weather Preferences: Continental winters & summers.
  • Location: Cleeve, North Somerset
30 minutes ago, Supacell said:

Do you know if there is an archive anywhere showing 2000s and 1990s lightning strikes?

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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset

I don't know why, but there's something about about it that makes me laugh.

nmmuk3hrprecip.thumb.png.37649454f774952af338f0f66b278ec2.png

nmmuk3hrprecip-1.thumb.png.cd1f03b8b6d7773efe7a89ec25d2d765.png

nmmuk3hrprecip-2.thumb.png.83e045449f5ffc70ef5a9b8f929d448b.png

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Posted
  • Location: Godalming
  • Weather Preferences: Plumes and streamers
  • Location: Godalming
10 minutes ago, MP-R said:

Do you know if there is an archive anywhere showing 2000s and 1990s lightning strikes?

I dunno if anyone had anyway of measuring it back then?

Too much hooch and britpop

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Posted
  • Location: Bristol
  • Weather Preferences: Thunderstorms and Snowstorms
  • Location: Bristol

 

18 minutes ago, Mapantz said:

I don't know why, but there's something about about it that makes me laugh.

nmmuk3hrprecip.thumb.png.37649454f774952af338f0f66b278ec2.png

nmmuk3hrprecip-1.thumb.png.cd1f03b8b6d7773efe7a89ec25d2d765.png

nmmuk3hrprecip-2.thumb.png.83e045449f5ffc70ef5a9b8f929d448b.png

You do know that that outcome is confirmed right! ;) 

If we look at the CAPE charts, there is no CAPE under that storm whatsoever, interesting to see as haven't seen this too often.

 

SB Cape.png

Edited by Ben Sainsbury
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Posted
  • Location: Bedfordshire 33m above mean sea level
  • Weather Preferences: Snowy and thundery.
  • Location: Bedfordshire 33m above mean sea level

It misses Bedford. Be off with you.

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Posted
  • Location: oxford, uk
  • Location: oxford, uk
6 minutes ago, Ben Sainsbury said:

 

You do know that that outcome is confirmed right! ;) 

If we look at the CAPE charts, there is no CAPE under that storm whatsoever, interesting to see as haven't seen this too often.

 

SB Cape.png

That's just a flaw in the netwx model. There is specifically no cape under the ppn, i assume, because it accounts for the change in atmospheric conditions, locally. 

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

The way I understand it - regarding widespread t-storms - is this: so long as there's a strong cap, like if we are under an area of HP, the likelihood of catching a storm is, in any one location, pretty close to zero...isolated potential humdingers?

But, if there's little or no cap, and should we be under a zone of relative LP, then storms might break out anywhere, be quite widespread but, barring a few exceptions, be mostly benign?

Which, given the forecasts, as we go through Thursday and Friday (of lowish SLP and high energy-levels and not too-much cap) there might be quite a few storms...?

The late, great Michael Hunt suggested that 2012mb, or lower, was a good starting-point!

I'm sure there must be an equation somewhere?:good:

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Posted
  • Location: Stoke Gifford, Bristol
  • Weather Preferences: Snow, Thunderstorms, Heat Waves, Tornadoes.
  • Location: Stoke Gifford, Bristol
35 minutes ago, Mapantz said:

I don't know why, but there's something about about it that makes me laugh.

nmmuk3hrprecip.thumb.png.37649454f774952af338f0f66b278ec2.png

nmmuk3hrprecip-1.thumb.png.cd1f03b8b6d7773efe7a89ec25d2d765.png

nmmuk3hrprecip-2.thumb.png.83e045449f5ffc70ef5a9b8f929d448b.png

Sods law if that actually comes to fruition. I'm in Newquay until Saturday! 

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Posted
  • Location: Cheslyn Hay, South Staffordshire. UK 159mtrs ASL
  • Location: Cheslyn Hay, South Staffordshire. UK 159mtrs ASL

A little bit of windshear usually works wonders, also a convergence zone helps.

 

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Posted
  • Location: Bexley (home), C London (work)
  • Weather Preferences: Thunderstorms
  • Location: Bexley (home), C London (work)

I would seriously take the NetWx model with a big fat pinch of salt at this stage.

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Posted
  • Location: Salisbury
  • Location: Salisbury
48 minutes ago, Ben Sainsbury said:

 

You do know that that outcome is confirmed right! ;) 

If we look at the CAPE charts, there is no CAPE under that storm whatsoever, interesting to see as haven't seen this too often.

 

SB Cape.png

Becaaause it shows where it has used all the cape up! Boom! Haha

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Posted
  • Location: Godalming
  • Weather Preferences: Plumes and streamers
  • Location: Godalming
9 minutes ago, Ed Stone said:

The way I understand it - regarding widespread t-storms - is this: so long as there's a strong cap, like if we are under an area of HP, the likelihood of catching a storm is, in any one location, pretty close to zero...isolated potential humdingers?

But, if there's little or no cap, and should we be under a zone of relative LP, then storms might break out anywhere, be quite widespread but, barring a few exceptions, be mostly benign?

Which, given the forecasts, as we go through Thursday and Friday (of lowish SLP and high energy-levels and not too-much cap) there might be quite a few storms...?

The late, great Michael Hunt suggested that 2012mb, or lower, was a good starting-point!

I'm sure there must be an equation somewhere?:good:

I think you're missing out the critical part the trigger will play (but I don't yet know what that trigger is).

In theory it goes like this: big build up of CAPE under the HP cap, then as the forcing comes into play this is pushed into a release of energy - i.e. Tstorms

Forgive my lack or research on the possible events for Thursday, I have a "severe weather" course on DVD my OH got me and need to watch it to patch knowledge holes... but I think I've got the general gist?

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Posted
  • Location: Belper, Derbyshire
  • Weather Preferences: Thunderstorms
  • Location: Belper, Derbyshire
1 hour ago, MP-R said:

Do you know if there is an archive anywhere showing 2000s and 1990s lightning strikes?

To be honest I don't. There is the link that Weather History posted but to be honest I can't understand it as it is all in German :D

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Posted
  • Location: Bexhill-on-sea, East Sussex (11.8M ASL)
  • Weather Preferences: Thunderstorms, snow, and wind storms
  • Location: Bexhill-on-sea, East Sussex (11.8M ASL)
3 hours ago, SenlacJack said:

I was on the seafront in Hastings watching as that epic storm came across The Channel and barrelled into Kent and Sussex. It's the most spectacular storm I have ever seen in the UK. Here is just one of the many good videos on YouTube.

 

 

 

This is one of the best thunderstorms I ever witnessed. I had just come back from holiday, sweating and tired. I noticed that all my neighbors were standing outside, and were watching that incredible wall cloud roll in. On the other side of the sky it was completely blue. 15 mins later and large hail, frequent CGs, gusty winds and biblical rain was falling. It cleared away, and I made the mistake of going to sleep, as an even more intense line of thunderstorms developed later in the night and apparently persisted for a few hours. (The evidence is on Blitzortung.

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Posted
  • Location: Beverley, E Yorks, 19m ASL
  • Weather Preferences: Snow, Thunder - not necessarily at the same time!
  • Location: Beverley, E Yorks, 19m ASL
12 minutes ago, LightningLover said:

This is one of the best thunderstorms I ever witnessed. I had just come back from holiday, sweating and tired. I noticed that all my neighbors were standing outside, and were watching that incredible wall cloud roll in. On the other side of the sky it was completely blue. 15 mins later and large hail, frequent CGs, gusty winds and biblical rain was falling. It cleared away, and I made the mistake of going to sleep, as an even more intense line of thunderstorms developed later in the night and apparently persisted for a few hours. (The evidence is on Blitzortung.

It's a shelf cloud or arcus. A wall cloud is a different phenomenon associated with a mesocyclone. This is an outflow feature pushing the warm air up ahead of it.

Spectacular either way. I love them!

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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

Day 2 Convective Outlook

VALID 06:00 UTC Wed 05 Jul 2017 - 05:59 UTC Thu 06 Jul 2017

ISSUED 20:35 UTC Tue 04 Jul 2017

ISSUED BY: null

... N WALES / N MIDLANDS / N ENGLAND / S SCOTLAND ...

Diurnal heating of warm and relatively moist surface airmass will likely develop some marginal instability across these areas - though in reality, surface-based parcels likely capped by a warm nose around 850mb suggesting lightning rather unlikely given limited depth to any convection. Given also little signal from most NWP output (ignoring GFS with its dewpoints of 16-18C vs EURO4 with 11-13C), have refrained from issuing a LOW threat level for now - but will need monitoring. Some residual elevated instability may also produce the odd shower over the Midlands into East Anglia too.

... S ENGLAND / S MIDLANDS / HOME COUNTIES / S WALES ...

Upper trough west of Iberia will continue to disrupt southwards, backing the flow and allowing advection of high WBPT airmass from Biscay to occur into southern England on Wednesday night. Falling heights aloft will result in an increase in coverage of elevated thunderstorms, though the exact forecast evolution is marked with some uncertainty.

The vast majority of guidance suggests a few thunderstorms will develop over the English Channel and/or S/SW England 23 - 02z, expanding in coverage through the remainder of Wednesday night as the focus shifts northwards and eastwards over S Britain as the new warm front lifts north - hence in a broad sense, probabilities per given location increases as you head farther north and east across the SLGT area. However, the ECMWF has been fairly consistent in keeping the main upper forcing a little farther south, and hence any thunderstorms may only graze the extreme south coast towards the end of the night. At the same time, it also allows more activation of the frontal boundary towards Northern Ireland and western Scotland. Given the ECMWFs history of generally having a good handle (compared to many other models) on medium-level instability events, this casts a little doubt on how widespread thunderstorms may be over southern England - though the degree of instability and very steep mid-level lapse rates would suggests any thunderstorms that do occur would be prolific lightning producers, perhaps capable of producing some hail and gusty winds. A MDT may be issued should confidence improve.

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-05

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