Storms and Convective discussion - 16th June 2021 onwards

[A Face like Thunder]

Very oppressive here in S Cheshire and could do with a storm to freshen things up!

[Turquoise]

considering my area has a SLT warning....its lovely and sunny here. Could this the 12th time in a row where thunderstoms are forecast here and we have a sunny day instead?

[Dangerous55019]

A very oppressive afternoon here in North East Wales

The sky is building up nicely… Much more promising looking than last weekend! 
 

Sadly I don’t think it’s gonna go bang… But still nice to see things brewing up. ?

[Chris.R]

Rather unexpectedly I have a torrential shower going on at the moment which seems to be back building. Wasn’t expecting anything today because of the seabreeze although this seems to be less of a feature now. Still looking good for tomorrow.

Edited July 10, 2021 by Chris.R

[Turquoise]

so once again for the 12th time in a row downpours and thunderstorms forecast for this town and its been a glorious sunny day without hardly a cloud. I know forecasters get it wrong but to be completely opposite 12 times in a row is frankly disgraceful. Plans get changed because you expect heavy rain but never turns out to be that way. Surely models cant be that wrong all the time. 

[Azazel]

Storm passing north of Andover just dropped a really quite decent funnel. Pics shortly.

[matty40s]

Something is afoot near Northampton...

[summer blizzard]

How widespread will these tonight. Look severe but scattered.

[Azazel]

Too far away and at a crappy angle to get any beautiful shots but 100 percent a funnel. The end was moving up and down like a snake.

[Kirkcaldy Weather]

Developed and lingered to the west earlier today and a bit of mammatus was forming 

[Azazel]

The cell also briefly formed a fairly suspicious looking wall cloud before it dropped the funnel 

[Jamie M]

Tony Gilbert's forecast from UKWW:

Slight Risk of Isolated Thunderstorms Wales, N England, Scotland & Ireland (Primarily) 11z-23z

This is a low level risk outlook.

Brief Synop;

Weakening upper short wave trough just SW of Ireland and is stacked vertically with a surface 'Closed Low'. This marginally and progressively increases upper lift and upper lapse rates for the UK . Upper jet loops cyclonically just south of the UK. Surface flow hard to correctly define, but looks primarily residual 'Polar Maritime'. Surface analysis suggests initial pre frontal troughing then occlusion much later from the SW.

Discussion;

Once again rather weak DLS (Deep Layer Shear) in place, right across the board. Steering winds look to move most storm cells northwards slowly at just 10 kts. Some ramping of surface temps likely to give say 19-20 deg C. Though some good surface moisture looks to build within convergence zones through the afternoon enhancing CAPE possibly to a basic level of 500 J/KG WRF model and a tad less GFS 400 J/KG. WRF forecast soundings look to cap off tops at around 22,000 ft. So thunder at best looks rather isolated and sporadic in nature! Surface convergence looks to be the key here combined with initial convective orographic lift over the Pennines. LCL (Lifted Condensation Level) looks to build slowly to surface during the late afternoon, where we could see another round of FC reports, specific to convergence boundaries at surface. Upper 300mb humidity values do not show any isolated forced increase in moisture at that level; I use this as a tool to work out projected cloud tops. A fairly moist deep vertical profile, but not saturated. This therefore is still workable if surface temps and dew points can build sufficiently through the day.

I have added some experimental FC risk boxes based a number of forecast overlay conditions; Which include Dew Point depression, surface convergence vector, CAPE, and weak LLS. The weak Low Level Shear is necessary for low level updraft formation to occur within a weakly deeper layer sheared environment. ; Conversely when convection is deeply sheared we look for the best LLS available. Because the updrafts are strong and have longevity. Within a weak convective set up we work on quite the opposite scale; Low level updrafts are at best frail and can only develop slow rotation when they are not distorted or torn vertically by any strong LLS. 

[Jamie M]

Crippling rain

[Chris.R]

having some good insolation this morning here. 19.1°C.

[Argyle10]

Will this sustain when it comes inland? 

[alexisj9]

Don't know, but hopefully this bodes well for the se tomorrow, looks like the juice is well and truly there.

[Harry]

16 minutes ago, alexisj9 said:

Don't know, but hopefully this bodes well for the se tomorrow, looks like the juice is well and truly there.

Yes tomorrow looking good for my neck of the woods - just a bit frustrating as I’ve been off this past week and I’m back working tomorrow

[staplehurst]

12z Camborne (Cornwall) ascent highlights the mid-level instability responsible for the elevated thunderstorms in the vicinity of Devon and Cornwall - convection initiating from around 1.5km (5,000ft) above the ground, but very moist profile below this level so areas of low cloud beneath the main convection. Just over 200 J/kg CAPE, much of this in the mixed phase region - ideal for lightning production.

Overall the profile matches the 00z ECMWF run reasonably well, however it appears the 450-550mb layer is cooler in reality than modelled - the net result is steeper mid-level lapse rates and therefore a more favourable environment for thunderstorms. This has clearly been instrumental at increasing the amount of instability and therefore producing lightning more than perhaps initially expected. 

[summer blizzard]

Showers are developing around here and moving more or less north but a bit too sporadic.

[Nick F]

Afternoon, 

Looks like Devon and Cornwall are getting some rumbles from convective rain moving in this afternoon, as nicely explained by Dan above. Some storms rumbling away over Moray too, thanks to sea breezes converging over NE Scotland. 

Monday looking rather interesting for SE England, quite an unstable airmass pretty early on in the day in the morning.

UKV CAPE and winds Mon noon

EC CAPE and winds

Convergence zone indicated south of London late morning that then moves north into afternoon, UKV and EC showing in excess of 1000 j/kg CAPE late morning in some spots.

PWAT of up to 32 mm and fairly slow-movement suggest a a fairly high risk of localised flooding. 

UKV ppn Monday 13-15z:

EC ppn for Mon 12z + 15z

MO rain warning

Slow-moving heavy showers and thunderstorms breaking out elsewhere across British Isles on Monday in response to surface heating and breeze convergence and orographic lift.

Edited July 11, 2021 by Nick F

[Delka]

Still managed to avoid storms or anything interesting, passed through peterborough yesterday for a couple hours and they were still pumping out water from the friday flooding next to the bus station and a car park opposite the train station was still waterlogged

[summer blizzard]

Showers much more widespread now from about north of Leeds. More optimistic.

[ChannelThunder]

Quite a few sferics out in the channel that appear to be slowly edging this way. Today has caught me out a little as I wasn't expecting anything at all!

[Guest]

Got some bangers heading in from the channel IOW east favourite currently given the usual standard eastwards propagation of sferics 

[Supacell]

A few posts hidden as they are either more appropriate for the No Storms club moaning thread or not relevant at all.

If your post is about how you don't get storms or attacking other areas for getting storms when you think your area doesn't then please don't put it in here. I am bored of reading it and I expect others are too. Cheers.