Storms and Convective discussion - April 2024

[Paul]

 Thunderspotter Everything should be sorted again now. We've had a couple of brief problems, one around lunchtime and one just now. It should be all good from here on in  

[Met4Cast]

A plume of very warm theta-e 850hPa (>40c) will destabilise and track NWards across northern France behind a broader warm front tomorrow. Initially surface based, these storms will become increasingly elevated as they track northwards into southern England. 800-1000J/KG of CAPE combined with 30-35kts of deep layer sheer will allow storms to become organised & sustained as they cross the English Channel.

Locally severe weather is possible across northern France with severe wind gusts, heavy rain & large hail associated with possible supercell storms and a broader tornado risk. For the UK, the elevated nature of storms suggests a reduced severe weather risk however heavy rain & frequent lightning can be expected.

There remains a lot of model variation on where these storms will track. SE/CS remains the most likely outcome with landfall probably east of the IoW but west of Folkestone as a rough estimate. Some modelling (UKV in particular) suggests a much further westward track into SW England/up into Wales but this remains on the extreme western end at the moment with models such as AROME/EC remaining consistent with a more eastern track.

 

[Thunderspotter]

 Paul Thank you! Muchly appreciated from all of us here  

[ChannelThunder]

Wow; UKV 12z is even better!

[Met4Cast]

 ChannelThunder Seems to be on the western end of the envelope compared with other models at the moment, EC/AROME for example have been consistently further east. I wonder if this is a case of the UKV underestimating elevated convection further east and instead running with the broader rain band associated with the warm front/trough. 

Not buying it's output currently, would like to see some support from other models first.

[CoventryWeather]

 Met4Cast would you expect a more northerly path then through the West Midlands and North Wales? 

Still surprised to see no elevated showers or storms before that suspected MCS. Would have thought there would be considering the airmass and instability. 

[Eagle Eye]

I'm going to say it. Nowcasting event. Models are making little sense and still can't agree with each other. Best I can do is base it off model output unfortunately. 

[Josh Rubio]

Purely from an IMBY perspective, I hope it tracks further north and east, taking it through Central England.

[viking_smb]

 Eagle Eye i agree, its very weird to have this setup, i think nowcasting is the best.

[Met4Cast]

 CoventryWeather

Really difficult to say at this stage. UKV is probably too far west, AROME 12z has shifted west slightly but still favours broadly the same areas as before, i.e SE into CS Eng perhaps the Midlands. Whether there will be much in the way of lightning further NW though remains to be seen. 

Very tricky forecast but impressive amounts of CAPE being shown for the time of year.

Edited April 30 by Met4Cast

[viking_smb]

 Met4Cast I got a feeling the storms once they hit landfall they will use the energy up pretty quickly

[Thunders]

 viking_smb wouldn’t be surprised but not much agreement anywhere so we’ll just have to wait and see

[Gonzolio Martinez]

Looks like things have kicked off in France

But as son as I say that, it looks like it's died again

Edited April 30 by Gonzolio Martinez

[Eagle Eye]

 Gonzolio Martinez wrong day, it's tomorrow. 

[Wivenswold]

Any action (and I'm not hopeful) will be in the eastern half of Kent and East Anglia tonight, it's the Southern counties' turn tomorrow.

[Neilsouth]

All this talk of storms tomorrow night, and today was completely wrong. They said the chance of the odd shower, and it's been chucking it down for over an hour now with no let up. It's like here's your nice weather and here's some more rain again.

[Gonzolio Martinez]

 Eagle Eye  Ah, I saw something about potential in EA this evening and got the 2 things conflated

[Met4Cast]

This is an impressive skew-T sampled just off the Kent coast tomorrow evening;

CAPE approaching 2,000J/KG with strong elevated convection coupled with strong DLS suggests the potential for some very active elevated thunderstorms into the SE tomorrow night, likely travelling NWards into the Midlands region (albeit weakening).

I suspect AROME is overcooking the values here slightly. Don't be fooled by the precipitation further west, bulk of any activity will be on the eastern side of any precipitation field. 

[viking_smb]

 Met4Cast  thanks mate, calmed my nerves even further

 

what does the effective layer mean please?  and the plotting on the top right 

Edited April 30 by viking_smb

[CoventryWeather]

Those couple of cells over France definitely a good sign for the upcoming days. 

The recent Arome only showing 700 CAPE around that area too, which seems low to be producing lightning at that intensity. 

[viking_smb]

 CoventryWeather surface based 

Edited April 30 by viking_smb

[weatherobsuk]

UKV and NW-SR are continually pushing Wednesday night's convection further southwards with each run so it's difficult to pin-point the exact area i'd personally like to be intercepting the storms given the current uncertainty. If I had to make a guess (and a last-minute chase) i'd set-up somewhere around Thatcham and then use the M4 to quickly head west if needed, using the MWay to get as much time close to the core before it exits out over the Bristol Channel.

[Eagle Eye]

I'm personally choosing the AROME for purely that I want a storm. Might be a little greedy but oh well. 

Edited April 30 by Eagle Eye

[viking_smb]

 Eagle Eye what does the base reflectivity mean please?

[Eagle Eye]

 viking_smb That's just rainfall from the lowest elevation scan.