Storms and Convective discussion - April 2024

[Eagle Eye]

Convective Outlook️ 

A mass of rain from a low pressure system should clear by late morning or early afternoon in the south and mid afternoon further north leaving behind some energy forced with a wind convergence zone in England. Meanwhile in Ireland similar lines of convergence should form and help convection with rising low-level temperatures amidst slightly falling pressure. 

 

Bands of forcing behind the clearing low pressure over England should allow for some showers to be forced where energy can rise the most. This is most likely in areas where the sun can come out, just behind the strongest of the forcing bands which hug close to the low, but so does the cloud. Limiting shower depth and the strength of convective tower potential, unless clearing can become more widespread in the higher forced areas mainly in the SE and east Anglia where showers also have more moisture to feed off for that convection.

 

Lapse-rates are strong enough for some small hail to form, but given the weak CAPE, I can't see much forming. Nor can I see much in the way of lightning because of the saturation associated with the area behind the low pressure system.

 

In Ireland the forcing bands are more connected with the potential for convection because of less favourable conditions for thick cloud cover. Therefore stronger lift is likely to occur here and force a few showers.

 

Stronger energy should take up more of the moisture even though it's quite weak and may lead to some heavy rainfall associated with these and they could also form into a proper line of convection by the afternoon if enough shearing were to be present. If they do, I suspect they could sustain further east than the models suggest hence why it's been extended into the Irish Sea and western Wales just in case, with a very small chance of a Supercell but shearing is lacking much strength to really push that risk.

 

However, most likely is that these are to remain rather weak and lightning is still a fairly small risk for now. Low-level lapse-rates are strong here and so small hail is possible however unlikely to be much more than 1/4 of an inch as the MLCAPE barely reaches past 300 J/KG. 

[Daniel_c150311]

Really feeling quite muggy here and thundery and the clouds are all of a sudden bubbling up quickly(just dtarting to hail now too 13:55)

Edited April 28 by Daniel_c150311

[chapmanslade]

For those of you storm starved in the UK, we had this cracker in France yesterday

[Cain]

Just had a hefty hail shower in south wales 

[Eagle Eye]

Convective Outlook️ 

During the early hours of Monday, a low pressure will track into Ireland which will clear into Scotland throughout the morning. 

 

Into the late morning / early afternoon period, Cape levels will start to once again pick up across Ireland at around 200J/KG to 400J/KG allowing intense showers to form across the Central spine of Ireland. These showers may develop into 1 or two thunderstorms however, lightning will mostly remain isolated / sporadic. 

 

Heading into the late afternoon/early evening period, these showers will track in a NE/E direction towards E parts of Ireland & Northern Ireland which will also bring the risk of isolated / sporadic lightning. Further shower development can be expected across. 

[Wade]

Latest ukv looking juicy for potential storms for those in the area around Birmingham on Thursday 2nd May, slightly too far south and west for me (highly unlikely to verify like that anyways) but something to keep an eye on for sure.

[Eagle Eye]

Day 3 risk for Wednesday that'll be updated by the time we get to Day 2 and Day 1. We're going to start doing this for events well signalled in advance. 

On Wednesday, an upper low is expected to form over Germany and Benelux, ushering in a relatively warm Theta-E airmass along the northern and eastern parts of the occluded front.

 

 

Forecast models indicate relatively high CAPE values (700 - 1500 J/kg) late on Wednesday, a rarity for May according to climatology. By late afternoon/early evening, a shortwave from the southeast will trigger the development of a wave along the frontal boundary, increasing the potential for dynamic rainfall. Isentropic upglide on the north-eastern flank of the frontal wave will lead to scattered elevated thunderstorms over southeast England during the evening hours. Strong deep directional and speed shear will facilitate organized thunderstorms, fuelled by warm, moist inflow from easterly low-level winds. The potential for upscale growth into a Mesoscale Convective System (MCS) exists as the thunderstorm complex drifts northeast across the Midlands. Hazards associated with this complex include hail, gusty winds, lightning, and localised surface water flooding.

[A Face like Thunder]

Talk on the Countryfile forecast last night of a front moving up from France into SE and E England tomorrow (Tuesday), with the possibility of some thundery activity.

[ChannelThunder]

 Eagle Eye do you mean as it drifts northwest? that's the direction it looks to be taking.

[Eagle Eye]

 ChannelThunder

Sorry yes meant northwest. So used to things moving northeast. 

[ChannelThunder]

 Eagle Eye aren't we just?  Very strange direction of travel for this event!

[Ben Sainsbury]

 ChannelThunder Very peculiar! Not sure how I'm meant to chase this one if confidence is high enough 

[CoventryWeather]

 Eagle Eye for once the Midlands seem primed for a decent night time event. I say that, there's a fair bit of uncertainty on timings - some want it Wednesday night and others Thursday Morning. But rather consistent on the track through the central midlands. Looking like a decent event at the moment, strong for the time of year. 

[ChannelThunder]

It'd be into UKV range now to keep an eye on without waiting for the 3/15z runs. However, it hasn't updated since 3z!

[Allseasons-Si]

 Eagle Eye That has piqued my interest as i am on mornings this week (6am-2pm),...thank you for the update

it has been a whoefull start to spring to say the least and it's time for the incandescent cool weather to step aside now

[Lt. Dan]

 A Face like Thunder Maybe, just maybe...

[ANYWEATHER]

 ChannelThunder UkV is total rubbish

[ChannelThunder]

Interesting that the Met Office are fully behind their model and not entertaining that this event could just as well be further north and east. Aidan mentions frequent lightning for the southwest:

 

[CoventryWeather]

 ChannelThunder seems an outlier at the moment, but let's see. Probably end up being a mid ground solution, as the ECM is still the furthest north. 

[A Face like Thunder]

 ChannelThunder Interesting. In 24 hours, we seem to have lost the possibility of any storm activity in the South and SE of England tomorrow and gained a more likely scenario of t & l in the South West and S Wales on Wednesday into Thursday.

[Windblade]

 A Face like Thunder Yeah, I read about that in the netweather forecast for yesterday (read it today). keeping an eye on that, as generally round these parts the last few years our best chance of a night time storm is an import rather than anything home grown which usually has no trigger round here anymore for some reason. Friday looks like it may have a bit of potential as well but will need to keep an eye on things nearer the time.

[ChezWeather]

Well, 2024, another year, another storm season! good luck everyone, i'll be out chasing within a local-ish vicinity this year, always happy to head to the great plains of Linconlshire for some storms though! 

[viking_smb]

i'm agreeing with eagle eyes take on it, it is a very unusual setup

I reckon it will be more midlands and north west areas that will get this 

 

@Eagle Eye any update please?

 

this low may not even develop

Edited April 29 by viking_smb

[Zak M]

 viking_smb Inside sources have told me that 99% of CG lightning from this system will strike over Cardiff I'm afraid.

[Eagle Eye]

 viking_smb

Update coming tonight. I suspect we're going for a small slight for now but that may move in area depending on 15Z UKV and model updates. This looks to be a moderate eventually as long as it remains on the models.