Storms and Convective discussion - 28th July 2019 onwards

[Supacell]

A break in the storms, ideal time for a brand new thread. After the heat and storms (for some) last week it is back to more usual British summertime weather antics for the foreseeable. Of course this mix includes thunderstorms, of which some are possible on Tuesday. Met Office have already issued a warning for thunderstorms across the SW quarter of England and all of Wales. 

Please continue on with all convective and storm discussion. Old thread here:

Please can you use this thread to rant about lack of storms or raise your grievances on missing out.

 

[Greeny]

I'll kick this off with screen grabs and short snap video of the best lightning strike I saw on Thursday evening in Norwich. It came over in 2 separate waves, the second the most violent of the two, with wind gusts, large convective drops and loud thunder including a positive strike (the thunder I got on video). I hope to upload the whole video to YouTube soon.

Finally a decent heat breakdown for us that was worth while. Lightning was very frequent.

[cobbettp]

Hi everyone long time lurker and inspiring Weather man lol. I think with the approaching low pressure we will definitely see some instability in the coming days. Perhaps the heaviest showers or storms I would hazard a guess Cornwall, Devon followed by South Wales for a start anyway then moving N.E later. Good luck to everyone I would like to see some more storms here in Portsmouth

[Had Worse]

I'm near Padstow at St Issey, I swear blind I didn't bring the storm shield from the Manchester / Peak District area, I will deny all knowledge if somebody finds I have. I will blame some unknown person for planting it in my roof box.

Anyway, I'm upbeat on tomorrow and Tuesday, cant get a 4G signal on the beach so here at the caravan, I can.

[Flash bang flash bang etc]

Looks like a Cornwall corker which will head a shallow NEE direction becoming a Basingstoke banger as it heads towards the north of london turning into a Romford Rattler

[TJS1998Tom]

Looking for Tuesday here in Silverdale, will be annoyed if the one week I'm not in Lincoln they get another good storm. Otherwise if there's any storms at night like Ventusky is showing could be a good display

[stevofunnelcl]

great, got builders half way through re-doing my roof, and we're going to get heavy showers / storms and strong winds

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Mon 29 Jul 2019 - 05:59 UTC Tue 30 Jul 2019

ISSUED 20:16 UTC Sun 28 Jul 2019

ISSUED BY: Dan

On Monday morning, a shortwave will swing westwards from the North Sea across northern Scotland and the Northern Isles, associated with weakening elevated convection. As a result, a few showers are likely - the odd one perhaps gaining sufficient depth for a few lightning strikes. 

By the afternoon the main focus will shift to scattered surface-based convection across the N / NW mainland, eventually drifting northwestwards towards the Outer Hebrides. A few sporadic lightning strikes will be possible, although the % chance is considered sub-SLGT. Slack conditions with low-level convergence and topographic effects may allow the odd funnel cloud to develop. Showers here will gradually decay during the evening hours as daytime heating subsides.

Meanwhile a sharpening upper trough to the west of Biscay will evolve into a cut-off upper low associated with a cold pool aloft atop seasonably warm SSTs. The surface low, containing subtropical moisture and reasonably high Theta-W, will slowly drift northeastwards to SW England on Monday evening / night, containing a messy mixture of dynamic and convective precipitation organised into bands rotating around the low centre. However, with time the low is expected to gradually lose its frontal structures, with primarily convective bands then encircling the centre by Tuesday morning. 

Due to the near-vertically-stacked nature of the low (although some tilting to the NW with height), shear will be fairly unidirectional and hence rather weak, which combined with fairly moist profiles will tend to limit the lightning potential. However, reasonable instability of 300-600 J/kg CAPE could allow some sporadic lightning to occur from the most intense cells. One or two waterspouts / tornadoes are also possible.

http://www.convectiveweather.co.uk/forecast.php?date=2019-07-29

[Zak M]

@matty40s 

It’s just a little tent on the outside of the house to stop things like alligators coming in.

Moving on, I was in Tampa at Busch Gardens today and when I was leaving there was a little storm arriving and out of nowhere there was this massive bolt that hit less than half a mile away from me. I got a video but I unfortunately missed the bolt. It’s kinda cool though because you can hear everyone screaming before the crack of thunder. I’ll upload the clip later.

[ancientsolar]

So a Stagnant low between Monday afternoon and Wednesday night .. brings possibility of storms.. I would hazard a guess these could cause a fair bit of local flooding along with some interesting lightning shows.

appears the met office are onto it already 
https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-warnings#?date=2019-07-30&id=449e1700-3996-4616-a6ce-6bd6adaa86a2

Edited July 29, 2019 by ancientsolar

[ancientsolar]

There was some curiosity I think on 25th or 26th Friday or Saturday about some very torrential downpours across SE Wales , there was no clear direction in which they looked like they were travelling. 
Here is a timelapse of the same shower .. what should have been a thunderstorm  
 

 

[Summer Sun]

Outlook DAY 1 (valid: 29/07/2019)

By SWE |  Severe weather outlook DAY 1 |  29 July 2019

SYNOPSIS

A deep cyclone is moving across the Bay of Biscay towards the English Channel. A weakening upper low is moving across the Balkans towards the east while an upper ridge over Scandinavia weakens while very deep trough / low enters from the NW Russia.

DISCUSSION

ENH / SLGT risks have been issued for the Bay of Biscay towards extreme NW France and SW England with threat for severe winds, tornadoes and torrential rainfall. Peak gusts could excess of 110 km/h near the center of a deep low moving across the Bay of Biscay while some low-topped supercells with tornado threat are also possible due to marginal instability but enhanced LL shear / helicity.

http://www.severe-weather.eu/outlooks-day1/outlook-day-1-valid-29-07-2019/

[Summer Sun]

1 minute ago, Gordon Webb said:

GFS Cape / LI Levels For Tomorrow

Well. At midnight..

They're higher during daylight hours could be a thundery afternoon for some

[Gordon Webb]

4 minutes ago, Summer Sun said:

Well. At midnight..

They're higher during daylight hours could be a thundery afternoon for some

yeah I tried to do them as well but mucked up the order so that post that was quoted is now hidden to hide the outcome and I had hoped nobody had been quick enough to quote it , oh well can't have everything

Edited July 29, 2019 by Gordon Webb

[Summer Sun]

Thunderstorm warning issued for Wednesday

Yellow warning for thunderstorms issued

00:00 Wed 31 to 23:59 Wed 31

Further thunderstorms likely with a chance of flooding in places and possible travel disruption.

What to expect

• There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds
• There is a small chance of fast flowing or deep floodwater causing dangerous conditions.
• Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services
• Spray and sudden flooding could lead to difficult driving conditions and some road closures
• There is a slight chance that power cuts could occur and other services to some homes and businesses could be lost

Thunderstorms and outbreaks of heavy rain already affecting some southern and western parts of the warning area during the early hours of Wednesday then become more widespread through Wednesday daytime. In a few places these thunderstorms could produce 30 mm of rainfall in an hour and 40 to 50 mm in a few hours. Some parts of the warning area will miss the heaviest rainfall.

https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-warnings#?date=2019-07-31&id=64438111-ee05-49a5-84b8-6695f2af4228&details 

[BrickFielder]

Satellite infra red imagery from the early hours of this morning showed quite a dark core for the low pressure system out in the bay of Biscay. I would take this to show that the low pressure system was deepening quite rapidly at this point. From the imagery we can see a cooler air feed becoming entrained within the system which has been feeding the enhancement.

Lightning Wizard charts show a couple of things. Firstly significant propensity for spout development for the south west into the evening and overnight. Secondly a marked upper level trough swinging across the UK ahead of the center of the low.Thirdly quite strong convection gust potential south and east of the low pressure system.

Looking at Forecast SkewT's I can see weak instability for the south west late into the afternoon with quite a bit of wind sheer. For tomorrow we see a pretty moist profile all the way up (which suggests messy convection). I am not sure how much I trust these at the moment.

Taking all of this into account then the forecast filling of the low and tilting might be a bit delayed. Upper level temperatures associated with the low might be a bit cooler than forecast where cooler air has become entrained.I would not rule out the possibility of a slightly wider area (Southampton through south midlands and into wales) being at risk of thunderstorms late afternoon. Prime risk is going to be for the south west including into the night. Water Spouts and very weak tornadoes should not be ruled out for this area. Tomorrow at the moment looks a bit messy and I would not like to put much detail on it till we see how things develop today.

[Zak M]

Here’s the clip:

[Zak M]

Although moving on yesterday afternoon, i’m gonna talk about yesterday night. Oh my god. My first time seeing a supercell storm and seeing a LOT of frequent lightning. It wasn’t until 9pm onwards (2am in the UK) where the lightning really started showing off it’s power. Lightningmaps.org showed a frequency of that storm of 80 strikes per minute, although I can easily say, it was at least 5x more than that. I honestly won’t be surprised if this storm makes the headlines. It was the biggest storm I have ever seen and the last time I will ever see a storm as big as that.

Edited July 29, 2019 by zmstorm

[Raindrops]

Weak Mammatus clouds over Dublin right now, including a Buzzard, cool.

 

Edit: Clouds are filling the sky, Mammatus now becoming more defined.

Edited July 29, 2019 by Raindrops

[East_England_Stormchaser91]

1 hour ago, zmstorm said:

Although moving on yesterday afternoon, i’m gonna talk about yesterday night. Oh my god. My first time seeing a supercell storm and seeing a LOT of frequent lightning. It wasn’t until 9pm onwards (2am in the UK) where the lightning really started showing off it’s power. Lightningmaps.org showed a frequency of that storm of 80 strikes per minute, although I can easily say, it was at least 5x more than that. I honestly won’t be surprised if this storm makes the headlines. It was the biggest storm I have ever seen and the last time I will ever see a storm as big as that.

One place that is the top of my bucket list. Florida.

Between June and August, guaranteed 100% storms. It’s a game of clash of Gulf and Atlantic sea breezes and where the colliding point is. After that, outflow boundaries from initial storms fire up new ones all over! It’s a convective lovers heaven by the looks of it. Add a bit of wind shear, and yep, they can get supercells! 

Heres a very good one from Clearwater. Imagine sitting with a beer watching bolts from the blue! Classic clear cut +CG’s. Heaven. 

 

Edited July 29, 2019 by East_England_Stormchaser91

[Allseasons-Si]

Just thought i would capture a couple of screen grabs

Edited July 29, 2019 by Allseasons-si

[Allseasons-Si]

I have just looked at the bbc and met office video forecast's,it's going to be an interesting day that's for sure but i do feel for the northwest of England after all the rain they had yesterday and there could be further flooding,still,i am sure that some folk on here wouldn't mind if they get a good storm out of it

[Stormchick]

36 minutes ago, Allseasons-si said:

I have just looked at the bbc and met office video forecast's,it's going to be an interesting day that's for sure but i do feel for the northwest of England after all the rain they had yesterday and there could be further flooding,still,i am sure that some folk on here wouldn't mind if they get a good storm out of it

Im not exactly a forecaster, but looking at the storm, precip and CAPE charts - it looks like a whole bunch of rain and not a lot else for Bradford tomorrow. I can't see too much to jump up and down about- The charts are all just real 'messy'. Can you see what it is that is making the BBC and Netweather forecast storms for Bradford? What should I be looking at? 

[Stormchick]

1 minute ago, Stormchick said:

Im not exactly a forecaster, but looking at the storm, precip and CAPE charts - it looks like a whole bunch of rain and not a lot else for Bradford tomorrow. I can't see too much to jump up and down about- The charts are all just real 'messy'. Can you see what it is that is making the BBC and Netweather forecast storms for Bradford? What should I be looking at? 

p.s. If your response includes the phrase 'Theta W' you're gonna have to explain what that is!

[Allseasons-Si]

3 minutes ago, Stormchick said:

Im not exactly a forecaster, but looking at the storm, precip and CAPE charts - it looks like a whole bunch of rain and not a lot else for Bradford tomorrow. I can't see too much to jump up and down about- The charts are all just real 'messy'. Can you see what it is that is making the BBC and Netweather forecast storms for Bradford? What should I be looking at? 

The Netweather's automated forecast for Bradford tomorrow,it is run by the gfs

https://www.netweather.tv/weather-forecasts/uk/7-day/3803~Bradford

bbc's take on it

https://www.bbc.co.uk/weather/2654993

met office forecast 

https://www.metoffice.gov.uk/weather/forecast/gcwdpv169#?date=2019-07-30

i won't go on about specific's as it does look messy but Brickfielder  posted a good post above^