Convective / Storm Discussion Thread - 27th Feb onwards

[Weather-history]

8 hours ago, Weather-history said:

Do you know, I wasn't that impressed by the storm. A lot of the thunder was at altitude and although I got a storm it wouldn't be up there with some past storms I have experienced. Maybe it was the thunder part of the storm that knocked it down the list.

 

[Supacell]

18 minutes ago, Darren Bown said:

I remember September 2016 having a massive storm across NW England that moved into Yorkshire and NE England one late evening. That flooded central Manchester and saw some amazing lightning to my east.

That would have been September 13th, the same day that saw the hottest temperature of the year in the SE at 34c.

[Summer of 95]

July 1st 2015 was probably the most frustrating day here weatherwise of the past 5 years: after getting tons of horrid mid-level muck all day keeping the temp below 30C (which we finally reached on 19th July 2016, for the first time in 10 years) when places east had sun and 32C, in the evening storms spun up 10 miles away and moved northeast, away from my direction. 

Now 22nd August 2015 on the other hand, that was a cracker. Quite short lived but the lightning was so constant it was like being in a disco with flashing lights, and booming seemingly coming from all directions. 

13th Sept 2016, yep that was a decent afternoon of thunder and lightning too. Really saved that month for me which was otherwise a bit of a let down (didn't even top 25C that month, 30C+ in the east again)...

There were a couple of overhead storms here in July 2014 I remember (one at night) and isolated ones on 3rd Aug 2013 and overnight 20/21 Aug 2011, but apart from those you had to go back to June 2005 for a "real" storm here before Aug 2015.  Those summers weren't just poor for sun and warmth, they were terrible for thunder despite often being wet.

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Thu 11 May 2017 - 05:59 UTC Fri 12 May 2017

ISSUED 14:22 UTC Wed 10 May 2017

ISSUED BY: Dan

WAA regime will continue into Thursday as a surface warm front lifts north across England and Wales. As a result, showery outbreaks of rain from primarily medium/high cloud will continue to nudge northwards in a rather sporadic / erratic fashion, with some embedded elevated convection possible given destabilisation of higher WBPT plume as the Biscay upper trough approaches - some sporadic, localised lightning is possible, but unlikely to be too widespread given marginal instability.

Behind this front, increasing insolation over southern England during the afternoon hours may allow surface-based deep convection to occur late afternoon into Thursday evening, given heating of this higher WBPT airmass, surface convergence and the approach of the Biscay upper trough. Question marks remain over the extent of the cloud cover, which may act as an inhibitor - however, the vast majority of NWP guidance still develop some thunderstorms, if rather isolated in some cases. A SLGT has been issued to highlight the areas at risk, with perhaps some small hail from the most active cells and a risk of localised flash flooding. Additional thunderstorms may also be advected from France / develop in-situ over the Channel towards S/SE England in the evening, but perhaps weakening as they do so.

http://www.convectiveweather.co.uk/forecast.php?date=2017-05-11

[Summer Sun]

Day 3 Convective Outlook

VALID 06:00 UTC Fri 12 May 2017 - 05:59 UTC Sat 13 May 2017

ISSUED 15:32 UTC Wed 10 May 2017

ISSUED BY: Dan

As the frontal boundary continues to lift north on Friday, a slack surface pressure pattern will evolve near the low centre. Diurnal heating will generate several hundred Jkg-1 CAPE under a broad upper trough, with low-level wind convergence aiding the development of scattered showers and a few thunderstorms for Friday afternoon and early evening, decaying after sunset. Some areas will likely be upgraded to SLGT nearer the time, but this is heavily reliant on the shape and position of the surface low, of which there is still too much uncertainty in guidance at present.

http://www.convectiveweather.co.uk/forecast.php?date=2017-05-12

[The PIT]

What about that storm that got stuck over Nottingham and didn't move for hours. We were stuck under that anvil for ages stopping any chances of storms here.

 

Looked at the local forecast and that isn't going for very much at all and mostly dry for the next few days.

Edited May 10, 2017 by The PIT

[Windblade]

Very calm here today with a lot of lovely Cirrus - usually a good sign of things to come.

[The PIT]

Local forecast has updated and still doesn't show anything of interest.

[Mapantz]

44 minutes ago, The PIT said:

Local forecast has updated and still doesn't show anything of interest.

To be fair, it'll be very hit & miss, so you won't get much in the way of detail from any of the forecasts. The usual 'radar & posts here' will be of more use. 

[Mokidugway]

Metcheck giving me some hope , cherry picking I know 

[Dangerous55019]

Just been out with the dog before I go to bed, and I have to admit that I was quiet shocked to see the cloudscapes looking so full of promise!

As I personally wasn't expecting to see any form of development until tomorrow... No guarantee of a storm I know, but still an encouraging sign 

[Mokidugway]

3 minutes ago, Dangerous55019 said:

Just been out with the dog before I go to bed, and I have to admit that I was quiet shocked to see the cloudscapes looking so full of promise!

As I personally wasn't expecting to see any form of development until tomorrow... No guarantee of a storm I know, but still an encouraging sign 

Does look like there's some instability moving in to your south , cloudy daze will be getting excited now 

[A.J]

looks like some elevated stuff breaking out along the warm front over the Channel Islands

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Thu 11 May 2017 - 05:59 UTC Fri 12 May 2017

ISSUED 20:00 UTC Wed 10 May 2017

ISSUED BY: Dan

WAA regime will continue into Thursday as a surface warm front lifts north across England and Wales. As a result, showery outbreaks of rain from primarily medium/high cloud will continue to nudge northwards in a rather sporadic / erratic fashion, with some embedded elevated convection possible given destabilisation of higher WBPT plume as the Biscay upper trough approaches - some sporadic, localised lightning is possible, but unlikely to be too widespread given marginal instability.

Behind this front, increasing insolation over southern England during the afternoon hours may allow surface-based deep convection to occur late afternoon into Thursday evening, given heating of this higher WBPT airmass, surface convergence and the approach of the Biscay upper trough. Question marks remain over the extent of the cloud cover, which may act as an inhibitor - however, the vast majority of NWP guidance still develop some thunderstorms, if rather isolated in some cases. A SLGT has been issued to highlight the areas at risk (primarily Surrey/north Hampshire westwards to Somerset, then north and west from here across SW Midlands to mid-Wales), with perhaps some small hail from the most active cells and a risk of localised flash flooding. Additional thunderstorms may also be advected from France / develop in-situ over the Channel towards S/SE England in the evening (hence the SLGT here), but with lower confidence and perhaps weakening as they do so.

http://www.convectiveweather.co.uk/forecast.php?date=2017-05-11

[Mapantz]

.. just an Arome animation:

[Convective]

Will revise tomorrow around noon, but for now:

[Paul]

Finally some weather!

Anim from the 12z Netwx-SR

[toggerob]

The majority of the cells tomorrow afternoon are missing the Midlands/NW, but nicely placed over Wales for us in the Peak District to see them from the SE dry-side. Might be worth taking a wander up to western-facing slopes of the Peak District (Sponds Moor/Shining Tor/Roaches) to snap some good structures.

[Flash bang flash bang etc]

Look at that little rainy front passing over the channel... ties in nicely with suggestions of possible limited elevated convection overnight tonight in the far south.

Not saying it will, but keeping a watchful eye on it...

[Mapantz]

 

[Flash bang flash bang etc]

2 minutes ago, Mapantz said:

 

Think anything will come of it?

[Mapantz]

1 minute ago, Flash bang flash bang etc said:

Think anything will come of it?

I doubt it. TT index isn't too shabby, but marginal MLCAPE. 
The warm front may pep up on the radar over the next few hours, but its likely to weaken after hitting southern counties. An isolated rumble, or some elevated lightning a possibility. It'll be a far better opportunity tomorrow, for areas within that warm sector. I'll plump for  somewhere between Gloucester and @Arnie Pie hehe

[Dorsetbred]

It has weakened and is weakening as time goes on, here there was nothing (contrary to the predictive radar).

[NO LONGER POSTING]

The stuff moving up north out of the channel now was never going to be thundery. Perhaps a very slight chance of the odd rumble. What it in fact does, is introduce more favourable conditions for storms 

Edited May 11, 2017 by Surrey

[Supacell]

Everything pretty much going to plan at the moment with some light showers moving northwards from the channel into south-western England. These showers continue to push NW into Wales through the morning. So here goes my predictions.....
It is later on this afternoon onwards that I expect heavy showers and thunderstorms will break out. The thinking is that they will initiate along a line from the west of London to Bristol, maybe following the M4 corridor and also possibly somewhere close to and along the Welsh borders. Through the evening these develop and expand in coverage as they move slowly in a NW'ly direction. GFS has the strongest CAPE to the west and this is where I expect storms to be strongest. My red area shows where these storms are likely to be. This area of storms will be very hit and miss and to be fair most people will miss. However, where they do occur they could be briefly quite intense with locally high rainfall totals in a short space of time, gusty winds and small hail. There is a risk of localised flooding and this will be made worse by the fact it has been so dry and so rainwater could stand on the surface for longer. Wind shear is weak and so organised/severe storms are not likely.

Within the yellow box, there is still a risk of some thunderstorms although the risk is lower. Some models (NMM) break out the storms a little further north and so this would bring more of the Midlands and North Wales into the firing line. However, the risk here is lower than in the red box. Any storms that form during the afternoon/evening will continue to drift NW. Euro4 is still out on its own in thinking that very little will break out this afternoon, this worries me a little with regards me heading south to chase today.

Further thundery spells could then move up from the south later on today and into the first part of the night. The best chance of getting thunder from these tonight is further south, nearer the south coast. As they move northwards overnight and into tomorrow morning they look to lose most of their thundery activity.

For northern areas it looks likely to be tomorrow afternoon and evening where thunderstorms will occur. However, this will be reliant on residual cloud cover left from the overnight rain being able to clear early enough for temperatures to rise. Once the sun does break through across England and Wales it will not take long for temperatures to shoot up into the high teens/low twenties under a warm, humid airmass (today and tomorrow).

Edited May 11, 2017 by Supacell