Storms and Convective discussion - September 2023

[Nantes storm factory]

1 hour ago, Eagle Eye said:

Any difference in environmental temperature or pressure enough for it to become a front or a trough. A shortwave trough or any front. To be more specific, there are other ways for or to occur though, anything that works to make low-level convergence and upper-level divergence can work as a forcing. Something like a jet streak (just research, it's pretty simple) or PV lobes that I often over talk about. Along with moisture advection near the surface forcing moisture convergence. Then there's the most complicated gravity wave, which is rare here.  Those are ones other to fronts and troughs that work. 

Absolutely spot on there .

[Allseasons-Si]

47 minutes ago, Ben Sainsbury said:

Both days are an improvement on latest probabilistic charts. Sunday I may add shows a small 15-25% of hail >2cm, which is something I've never seen over the UK since this product has been released. Also a 5% probability for 5cm hail too.

Ooooooh!!!,...i l ike the look of that for Sunday,thanks Ben.

47 minutes ago, Ben Sainsbury said:

Both days are an improvement on latest probabilistic charts. Sunday I may add shows a small 15-25% of hail >2cm, which is something I've never seen over the UK since this product has been released. Also a 5% probability for 5cm hail too.

Ooooooh!!!,...i l ike the look of that for Sunday,thanks Ben.

47 minutes ago, Ben Sainsbury said:

Both days are an improvement on latest probabilistic charts. Sunday I may add shows a small 15-25% of hail >2cm, which is something I've never seen over the UK since this product has been released. Also a 5% probability for 5cm hail too.

Ooooooh!!!,...i l ike the look of that for Sunday,thanks Ben.

[Aiden2012]

Oooo Sunday looks good and it’s my day off hopefully a chase day

[Allseasons-Si]

I don't know why it multy quoted like that^^

[WeatherArc]

Beautiful storm today in Ireland, incredibly photogenic   Looks like something you'd see in May on the Great Plains. 

[Ben Sainsbury]

3 minutes ago, Allseasons-si said:

Ooooooh!!!,...i l ike the look of that for Sunday,thanks Ben.

Ooooooh!!!,...i l ike the look of that for Sunday,thanks Ben.

Ooooooh!!!,...i l ike the look of that for Sunday,thanks Ben.

Liked the look of it so much you had to say it 3 times  

[Allseasons-Si]

2 minutes ago, Ben Sainsbury said:

Liked the look of it so much you had to say it 3 times  

Ha ha!

i was clicking reply and it wouldn't,...so i must of clicked it 3 times

[Allseasons-Si]

A few sferics on the breast peninsula by lightningmaps but not on blitz.

Edit,...showing on blitz now.

Edited September 8, 2023 by Allseasons-si
typo

[Flash bang flash bang etc]

We need thunder, lightning, hail, torrential rain and bars of chocolate.

 

like if you agree

[SummerShower]

1 minute ago, Flash bang flash bang etc said:

We need thunder, lightning, hail, torrential rain and bars of chocolate.

 

like if you agree

Maybe a tornado as well then, to lift the bars of chocolate from somewhere, into the cloud.  Then they can rain down

[Allseasons-Si]

3 hours ago, Eagle Eye said:

Sorry about no forecast for today earlier. Absolutely shattered and Jay wasn't available to do the map. Proper professionals.

We all understand mate

and we can't all keep our eyes glued to the screens 24/7,...you do your damn best so keep it up

Edited September 8, 2023 by Allseasons-si

[ChannelThunder]

Well, I'm very glad I got my fix abroad recently, as tomorrow night is looking worse with every model run down here. 

The central south/southeast's worst *ever* storm season? At least in living memory? 

[Woodboss]

On 05/09/2023 at 08:23, ChannelThunder said:

One year ago!

Still annoyed about my camera settings/choice of lens on this, but it did lead to me educating myself more on certain things about lightning photography that I was perhaps overlooking a little. Still, made a little bit of money off of two national papers!

 

I remember this night very well! By far the best that year! Great capture matey!

[Eagle Eye]

Here's my discussion for tomorrow. Working from 9 till 5 so best to put it here now even though Jay hasn't done the actual map yet.

There are a couple different modes and timings with these potential storms. I'll start with the most likely but also has the smallest ceiling of potential.

 

Ahead of a cold front, with fairly good DLS, showers and storms should form in Ireland and up into parts of western Scotland. These happen mainly throughout the afternoon in a stream along an area of 500-1,000 J/KG of MLCAPE along a tight PV lobe. With weak MLCIN and a fairly good trigger with PV lobe induced low-level convergence. This occurs with fairly high moisture and fairly weak saturation. So, all showers and some weak to moderate storms may well form.

 

High LLLR's and strong 3CAPE (100+ J/KG) allows for some small severe hail to form, potentially around 1-1.25 inches. There is potential for locally 2,000+ J/KG of MUCAPE and combine that with the large inflow layer and you could suggest, strong updraft speed for strong downdraft speed, however, weak downwards momentum within storm soundings will mean that downwards momentum won't be a particularly high percentage of the updraft speed and with restricted inflow strength, so hail is still going to be restricted compared to updraft strength. Strong buoyancy will help the hail, however, there are a lot of anti-severe hail factors mentioned before that keep it from being a significant factor in anything other than increasing updraft width+speed but not necessarily much of the downwdraft speed for the hail size.

Moving onto the Wales and the midlands-northern England part of the risk. There is quite strong capping in place and no real trigger. However, 2400+ J/KG of MUCAPE in places with widespread 1,000 J/KG of MUCAPE in an area of tropical moisture rates means that with fairly strong DLS, any low-level convergence available via localised orographic features or something like that, could spark a few severe isolated thunderstorms with a small chance of becoming a Supercell. Again, this happens in the afternoon and if storms can get going then it would be mid-afternoon initiation and into the late evening for storms.

 

Good buoyancy with a large inflow layer and good sub zero CAPE suggests some 1.5 inch hail is possible. The hodograph isn't really your typical C shape with the inflow which is fairly strong but still leaning towards the moderate side and so the hail is still being restricted to about 1.5 inches. The inflow layer is large compared to recently but still relatively small compared to events larger than 1.5 inches. Storms could potentially reach past 12km cloud tops which is quite high compared to your everyday thunderstorms, hence why they could be quite severe.

Finally, in the evening and overnight in the SW, some elevated thunderstorms could form. Not particularly large CAPE but good moisture and good modelling guidance suggests, these should happen. Previous events suggest some good lightning frequency potential as well.

Here's the current idea that Jay has but he's waiting till tomorrow which is fair enough but I can't do; (black outline is area of interest for lightning and also in my opinion, the severe outline I would think of as well.).

[Southern Storm]

18 minutes ago, Eagle Eye said:

Here's my discussion for tomorrow. Working from 9 till 5 so best to put it here now even though Jay hasn't done the actual map yet.

There are a couple different modes and timings with these potential storms. I'll start with the most likely but also has the smallest ceiling of potential.

 

Ahead of a cold front, with fairly good DLS, showers and storms should form in Ireland and up into parts of western Scotland. These happen mainly throughout the afternoon in a stream along an area of 500-1,000 J/KG of MLCAPE along a tight PV lobe. With weak MLCIN and a fairly good trigger with PV lobe induced low-level convergence. This occurs with fairly high moisture and fairly weak saturation. So, all showers and some weak to moderate storms may well form.

 

High LLLR's and strong 3CAPE (100+ J/KG) allows for some small severe hail to form, potentially around 1-1.25 inches. There is potential for locally 2,000+ J/KG of MUCAPE and combine that with the large inflow layer and you could suggest, strong updraft speed for strong downdraft speed, however, weak downwards momentum within storm soundings will mean that downwards momentum won't be a particularly high percentage of the updraft speed and with restricted inflow strength, so hail is still going to be restricted compared to updraft strength. Strong buoyancy will help the hail, however, there are a lot of anti-severe hail factors mentioned before that keep it from being a significant factor in anything other than increasing updraft width+speed but not necessarily much of the downwdraft speed for the hail size.

Moving onto the Wales and the midlands-northern England part of the risk. There is quite strong capping in place and no real trigger. However, 2400+ J/KG of MUCAPE in places with widespread 1,000 J/KG of MUCAPE in an area of tropical moisture rates means that with fairly strong DLS, any low-level convergence available via localised orographic features or something like that, could spark a few severe isolated thunderstorms with a small chance of becoming a Supercell. Again, this happens in the afternoon and if storms can get going then it would be mid-afternoon initiation and into the late evening for storms.

 

Good buoyancy with a large inflow layer and good sub zero CAPE suggests some 1.5 inch hail is possible. The hodograph isn't really your typical C shape with the inflow which is fairly strong but still leaning towards the moderate side and so the hail is still being restricted to about 1.5 inches. The inflow layer is large compared to recently but still relatively small compared to events larger than 1.5 inches. Storms could potentially reach past 12km cloud tops which is quite high compared to your everyday thunderstorms, hence why they could be quite severe.

Finally, in the evening and overnight in the SW, some elevated thunderstorms could form. Not particularly large CAPE but good moisture and good modelling guidance suggests, these should happen. Previous events suggest some good lightning frequency potential as well.

Here's the current idea that Jay has but he's waiting till tomorrow which is fair enough but I can't do; (black outline is area of interest for lightning and also in my opinion, the severe outline I would think of as well.).

Great update, much appreciated

[Uncertainty]

Arpege, UKV and Arome both going for a narrow cluster of strong / severe storms from late afternoon Sat east mids —> N Lincolnshire or perhaps even further N of the Humber estuary. Harmonie having absolutely none of it. Would prefer to get x model agreement on initiation as without much forcing other than the convergence zone there’s a potential bust there. Especially as the tracks outlined by the models are right at the northern tip of the MO warning. Notwithstanding that they would potentially be quite notable if they get going. Fairly slow moving storm motion (slowly ENE), photogenic structure from high cloud tops, prolific lighting as well as reasonable hail would be possible. 

Sunday looks a different story. Cape in the 2000+ range and much more vorticity, could get high end severe for U.K. standards towards NE England, Depending on the timing of the overlapping deep layer sheer.
 

Looks like a bit of an outbreak and it could be S Scotland and central parts of England perhaps get in in the action too.

[Ben Sainsbury]

AROME 18z possibly one of the best charts I've seen modelled for the UK on Sunday. Locally 2,000J/Kg+ in a moderately sheared environment and develops into what appears to be a brutal surface-based MCS for UK standards.

 

Edited September 8, 2023 by Ben Sainsbury

[Metwatch]

Just now, Ben Sainsbury said:

AROME 18z possibly one of the best charts I've seen modelled for the UK on Sunday. Locally 2,000J/Kg+ in a moderately sheared environment and develops in what appears to be a brutal surface-based MCS.

 

Simulated satellite speaks for itself. Tomorrow afternoon in Lincolnshire looks pretty beefy too.

[Southern Storm]

Another push west from this evenings 21z UKv @ 0100z Sunday morning 

If things continue as they have been, we're gonna need a boat to have any chance of seeing a storm

Edited September 8, 2023 by Southern Storm

[Rufus Butterfield]

10 minutes ago, Southern Storm said:

Another push west from this evenings 21z UKv @ 0100z Sunday morning 

If things continue as they have been, we're gonna need a boat to have any chance of seeing a storm

it’s going to be anyone’s guess so it’ll just come down to radar watching

[alexisj9]

24 minutes ago, Southern Storm said:

Another push west from this evenings 21z UKv @ 0100z Sunday morning 

If things continue as they have been, we're gonna need a boat to have any chance of seeing a storm

Hmm I hope it doesn't move to far west, as that shows the high is trying to stay a bit longer. I need a cool down now lol.

Edited September 9, 2023 by alexisj9

[Southern Storm]

10 minutes ago, alexisj9 said:

Hmm I hope it doesn't move to far west, as that shows the high is trying to stay a bit longer. I need a cool down now lol.

Yeah tell me about it, window wide open and it's not cooling down at all  

Let's see what tomorrows charts look like, but whatever happens, a cool down looks to be on the cards early on in the coming week.

[Cheshire Freeze]

At the moment for Sunday it looks like clusters of storms will break out around Mid Wales and into to the Welsh Marches into the early afternoon. Storm clusters then look to push NE towards the N Midlands and N England…potentially merging into an MCS later on across N/NE England.

I think the most severe weather may well occur at the crossover point I.e at the point the storms merge to form an MCS. Could be some very potent cells. I’d probably highlight the M62 corridor sort of area, perhaps Liverpool- Manchester-Leeds

EC-

ICON-

Edited September 9, 2023 by Cheshire Freeze

[Flash bang flash bang etc]

Quite a bizarre-looking outlook for next week if it ever materialises

[Gordon Webb]

hello

just an enquiry

Convective Weather has been quiet for weeks , just wondering if anything has happened ?