Storms and Convective discussion - 1st May 2022 onwards

[staplehurst]

Been keeping an eye on Saturday night for a few days (let alone any other potential beyond that) but forecast profiles just don't look that unstable. The models naturally have subtly different thermodynamic profiles which is partly why they differ in placement on areas of showery rain - not unexpected given the complexity of the evolution but also how far out we are. There is some decent shear (indicative of the warm air advection regime), but the profiles just look too warm aloft to create any decent instability. Primarily skinny and/or restricted in depth CAPE with fairly moist profiles which never really bodes well for a prolific lightning display.

If we could get the mid-level low over the Celtic Sea to shift further east and help cool the profile aloft that would help, but right now my gut feeling is most lightning will be on the French side and very little makes it into southern England. Still some showery rain from high-based convection though, some of this evaporating before reaching the ground. This is just Saturday night, beyond that there is less obvious upper forcing so we're relying more on subtle shortwaves around the upper ridge over Europe and so I suspect the detail for Sunday onwards will chop and change over the next couple of days as the models attempt to resolve these smaller scale features and their influence on the thermodynamic profiles.

Edited May 12, 2022 by staplehurst

[StormLoser]

Coming out of hibernation in storm-averse Reigate, I see Saturday night looks vaguely interesting. The Cutty Sark comes to mind, too....   

[Andy Bown]

On the 18.30 BBC forecast Chris Fawkes mentioned prolific lightning for Saturday night but not much rain, that is suggestive of elevated storms.

[BrickFielder]

 I don't think I would like to forecast Saturday at this point as it looks like the models are not really stabilised for that time frame. Looking at the Satellite pictures and Jetstream forecast for now then I can see evidence of a cut of low out to the west of Spain. This puts the High pressure between this low and the Jetstream running over the UK. Models then suggest this low pressure will lift out towards the UK.

  What you would expect is that thunderstorm potential will be concentrated at Jetstream left exit regions where winds diverge aloft. The suggested idea is that thunderstorms develop over France even though we are probably looking at upper anticyclonic (High) conditions there. Divergence aloft might arrive earlier than thunderstorm predictions. 

  Looking at the Jetstream forecast and low level winds forecast we have low pressure circulation aloft with cooler air aloft whilst high pressure conditions are suggested at the surface. When transitions happen upper and lower air conditions can disconnect, but the suggested disconnect feels more like models are playing catch up and the catch up is happening at upper levels quicker than lower ones.

  There is a thunderstorm risk for Saturday in my opinion with possibly at least a week of thunderstorm potential next week. I would be concerned about forecasting detail much more than a day ahead until I am happy models are handling the situation correctly. It is possible the modelling is correct so make up your own minds.
  
  

[ChannelThunder]

Well, despite some of the less-encouraging runs today, the 12z Euro is a good one; I'll bank that one right now! 

[Ben Sainsbury]

ICON & ARPEGE 18z runs both shift west with modelled precipitation for Sat Night, just remains to be seen how much instability builds and therefore the lightning risk.

[The Tall Weatherman]

The Latest GFS run isn’t shabby in the case of an MCS, 17 degrees at Midnight and Cape up to 1000! Day temps soaring past 25 In central London.

[Sprites]

11 hours ago, Andy Bown said:

On the 18.30 BBC forecast Chris Fawkes mentioned prolific lightning for Saturday night but not much rain, that is suggestive of elevated storms.

I wonder if he has got that the right way round 

[ChannelThunder]

UKV looks better for tomorrow night now, ECM also still encouraging. I'm cautiously hopeful.

[Harry]

While the precip projections for tomorrow night are improved, the MLCAPE is still very very weak (in fact, almost non-existent).

I am therefore struggling to see how we might expect to see much, if any, lightning.

On the plus side, however, Sunday night into Monday is looking good for southern areas.

 

[Eagle Eye]

34 minutes ago, Harry said:

While the precip projections for tomorrow night are improved, the MLCAPE is still very very weak (in fact, almost non-existent).

I am therefore struggling to see how we might expect to see much, if any, lightning.

On the plus side, however, Sunday night into Monday is looking good for southern areas.

 

Look at MUCAPE and Saturday into Sunday gets slightly better but agreed that I think the biggest one to look at at the moment is Sunday into Monday.

[Ben Sainsbury]

Agree with the above, Sunday night is looking much better and better model agreement. GFS & NMM so far showing up to 1000J/Kg of CAPE overnight, however DLS looking somewhat on the weak side probably 20-30kts max. Much greater risk of lightning however than tomorrow night.

EDIT: Honestly haven't seen this much model discrepancy for imported storms in a good few years now.

Edited May 13, 2022 by Ben Sainsbury

[Guest]

2 hours ago, Ben Sainsbury said:

Agree with the above, Sunday night is looking much better and better model agreement. GFS & NMM so far showing up to 1000J/Kg of CAPE overnight, however DLS looking somewhat on the weak side probably 20-30kts max. Much greater risk of lightning however than tomorrow night.

EDIT: Honestly haven't seen this much model discrepancy for imported storms in a good few years now.

Let’s hope they make further across the channel than last years which almost all hit an invisible super stable about 30mins out from the south coast. 

[ChannelThunder]

Some UKV snapshots, hinting at greatest lightning potential in the channel (surprise surprise), and two possible rounds of downpours:

[Nick F]

Good afternoon, have done a blog for Netweather on the thundery potential from the 2nd half of the weekend,:

Thundery downpours on the way for parts of the UK from Sunday

WWW.NETWEATHER.TV

---

A look at the potential for some heavy downpours and thunderstorms affecting parts of the UK during the second half of the weekend and through next week.

Will issue a Thunderstorm Watch tomorrow, if it looks more likely there'll be t-storms Saturday night into Sunday morning and during Sunday.

cheers

Nick F

[ChannelThunder]

38 minutes ago, Nick F said:

Good afternoon, have done a blog for Netweather on the thundery potential from the 2nd half of the weekend,:

Thundery downpours on the way for parts of the UK from Sunday

WWW.NETWEATHER.TV

---

A look at the potential for some heavy downpours and thunderstorms affecting parts of the UK during the second half of the weekend and through next week.

Will issue a Thunderstorm Watch tomorrow, if it looks more likely there'll be t-storms Saturday night into Sunday morning and during Sunday.

cheers

Nick F

Thank you, Nick. This kind of educational outlook is always really appreciated.

[Harry's House]

From what I have read, does any one think that we are in for a long thundery spell that lasts for perhaps over 10 days?

[ChannelThunder]

17 minutes ago, Harry's House said:

From what I have read, does any one think that we are in for a long thundery spell that lasts for perhaps over 10 days?

I wouldn't say so, it just never happens that way in this country. A few years ago, models showed something WAY more thundery than what they show for the coming week, but in reality, sadly it just didn't come off. In this case, I think the Atlantic will cut off any southerly flow entirely by the middle of next week.

[Ben Sainsbury]

The NMM 12z for Sunday night , tomorrow night looks a touch better too.

[Sprites]

That sounds like the opposite to a plume.....

Edited May 13, 2022 by Sprites

[Mapantz]

High PWAT may result in thundery rain rather than storms on Sunday?! Depending on evap, of course..

[ChannelThunder]

I think it's safe to say that the AROME is keen on this (Saturday night). A very loud and late night to be had in the Dorset-IOW area according to its 12z run, but we've all seen how it likes to over-do these situations!

[Ben Sainsbury]

30 minutes ago, Lance M said:

I think it's safe to say that the AROME is keen on this (Saturday night). A very loud and late night to be had in the Dorset-IOW area according to its 12z run, but we've all seen how it likes to over-do these situations!

AROME not showing a huge amount of instability however, that saying it does also seem on its own regarding tomorrow night developments.

Edited May 13, 2022 by Ben Sainsbury

[East_England_Stormchaser91]

Hmmm I’m very confused. Our local forecast has been on about a Saturday night event for a couple of days now, yet I’m still checking every detail of most runs, and I’m seeing nothing to back up their forecasts. Very little in the way of adequate surface or even elevated CAPE, fairly modest dew points. The only meaningful instability is way over the other side of the Channel in W/NW France. 
As also mentioned, Sunday night to me has a lot more potential. We shall see. Every day is a school day in meteorology. 

[Harry]

3 minutes ago, Ben Sainsbury said:

AROME not showing a huge amount of instability however, that saying it does also seem on its own regarding tomorrow night developments.

It has however boosted CAPE on the approaches to the SW - over 500 close to the coast at midnight. Precipitation looks impressive though.