Storms and Convective discussion - April 2024

[Eagle Eye]

 viking_smb Most likely but I wouldn't rule out the odd strike or two still. 

[Rush2019]

4 minutes ago, Eagle Eye said:

but I wouldn't rule out the odd strike or two still. 

The squall like system moving east is now producing strikes, Derbyshire way, Yorkshire could be in with a shout, it's very intense on the radar.

[CoventryWeather]

Monday Evening catching my eye a touch. 

South east possibly for a weakish plume event. 

Limited CAPE values however for the majority but closer to the continent seems like there's a significant amount there. 

Edited April 6 by CoventryWeather

[TJS1998Tom]

The rain is falling crazily heavy here atm, not had it this heavy in ages

[TJS1998Tom]

About 40 minutes ago there was clear skies with stars showing as well, didn't expect this but nothing thundery

[ChannelThunder]

 CoventryWeather Spotted this too this morning. Looks a bit Kent-Clipper'ey 

[Thunders]

 CoventryWeather i hope so

[Sprites]

European Storm Forecast Experiment - ESTOFEX

WWW.ESTOFEX.ORG

 

 

Extended Forecast
Valid: Mon 08 Apr 2024 06:00 to Tue 09 Apr 2024 06:00 UTC
Issued: Sat 06 Apr 2024 21:41
Forecaster: TUSCHY

A level 1 was issued from France into N-Germany mainly for severe wind gusts, large hail and an isolated tornado threat.

SYNOPSIS

The main story is a progressive longwave trough just W of Europe. This feature amplifies in response to a digging anticylonic jet along its upstream flank and sharpens throughout the forecast with an impressive amount of shear/curvature vorticity along its base but also next to an embedded vort max, which lifts towards UK. This scenario causes constant height falls from UK/France to the W-Mediterranean. IFS-ENS indicates some probabilites for weak cyclogenesis over the W Mediterranean but also highlights the lifting vortex over UK with tight clustering.
A robust lead wave is forecast to cross Benelux/NW Germany during the afternoon into the overnight hours from SW to NE.

E of this trough a record shattering subtropical ridge still covers most of the CNTRL Mediterranean with numerous waves cirling this ridge from Scandinavia into Russia.
Otherwise a quasi-stationary upper low still sits atop the far E Mediterranean with ongoing unsettled conditions.

Along the surface, a broad warm sector over CNTRL Europe gets framed by an eastbound moving meridionally aligned cold front over E Spain into CNTRL France and a wavy warm front, which runs from N France E/NE all the way to N Poland/Belarus.

Overall NWP guidance is stable in placing the synoptic features of interest including the lead wave over Benelux. EPS data indicates some uncertainties in how far this French trough will amplify and how far NE the vortex over the UK will move. At LL, IFS indicates a broad low pressure channel, extending E from the English vortex towards Benelux and into N Germany. Embedded potential weak cyclogenesis is indicated by numerous member maxima with weak pressure anomalies.

DISCUSSION

Due to the extended forecast range we do not yet go into too many details. In general the warm sector over CNTRL Europe will be the main focus for organized DMC activity with the following foci:

a) Cold front induced convection over CNTRL France, which evolves during the day along the boundary but also next to the orography (e.g. Massif Central). BL moisture is adequate but suffers from missing Mediterranean input due to the existing African airmass atop the W/CNTRL Mediterranean. Pockets of moderate MLCAPE with plenty of directional and speed shear should support a few NE ward moving supercells with large hail/severe wind gusts from CNTRL France to the south (drier BL with higher LCLs). Further north into the proximity of the warm front, a more humid BL should support also (near) surface based supercells with a growing tornado risk.

b) BENELUX into NW Germany. The passing short wave, falling pressure and a northward pushing warm front should be adequate for late afternoon/evening convection. Enhanced moisture pooling along the confluent LL wind field (the warm front) with some background support should assist in at least isolated CI. Kinematics are impressive and organized convection occurs with any structuring updraft. Either large hail for more elevated cells or cells with all kind of severe along/S of the warm front are forecast with initiation depending on mesoscale support. Of growing concern is a 60kt speed max. at 700 hPa, well anticipated from most models and pushing into W-Germany during the afternoon hours with impressive hodographs for well organized mesocyclones. Ongoing isues with CAPE magnitude, insolation (departing DIBS) and still uncertain final magnitude of (synoptic/mesoscale) lift preclude an upgrade for now. This acitivity shifts NE into N-Germany during the night with an ongoing severe risk.
We nudged the level 1 into SE UK to account for a temporal untable warm sector with adequate CAPE/shear for organized convection during the day. This however depends on the final mass response to the approaching vortex with ongoing uncertainties in NWP guidance. Still, confidence is increasing and hence the level 1 upgrade for now.

c) Lithuania/Latvia into N Belarus. Persistent SW-erly moisture advection beneath colder mid-levels assists in a broad plume of enhanced MUCAPE, overlapping with 15-20 m/s DLS. A passing short wave could support a few nocturnal thunderstorms along the wavy boundary with mainly a large hail and heavy rain threat. Although dust induced cloudiness is more likely in this area, this convective event seems to be decoupled from the BL, so there certainly is a conditional risk for a few organized storms. A level 1 may be needed if confidence in coverage and final CAPE magnitude increases.

... Spain ....

This area needs to be monitored regarding diabatic heating as not much modification is needed for a few multicells especially over N-CNTRL Spain with hail and heavy rain. Right now, messy storm mode with low-end CAPE precludes any upgrade for now.

...SE Europe ...

Beneath the upper low, scattered thunderstorms are forecast with heavy rain, strong to severe wind gusts and hail. The limiting factor will be reduced CAPE due to the worked-over airmass. A local upgrade may be needed especially over SE Turkey.

Edited April 7 by Sprites

[TJS1998Tom]

Forecast suggesting something thundery later but I suspect most likely heavy showers

[LightningLover]

Small  elevated storms followed by very strong winds?

[Eagle Eye]

Lots of differences for tomorrow mgohts potent potential storm risk with some severe hints. Most models have it sliding desperately just out of reach from us, but the UKV has more developments for the eastern parts and quite a strong system forming. Likely a case of we'll see what happens and model trends. 

This is occuring on a lobe of forcing within a deeper moisture band ejected from northern France area, leading to development of what appears to be a shortwave trough for those potential showers or storms within it. That band is forced up because of the low to the SW, the positioning of that being very important. 

3CAPE is just about warranting of severe potential, but I suspect the UKV would be more of an advection of that surface energy. This is given there's a deeper pool over northern France that's around 200 J/KG of 3CAPE according to the Swiss models. 

Hearing is very much sort of there, especially over the mainland parts. That may warrant some kind of severe threat, I'll wait till tomorrow to properly go into it. Whilst not major, the low-levels are especially sheared. 

Fairly decent CAPE on the UKV shown, but likely not enough for all the showers forced to have lightning within them, only mainly the ones in the SE. The UKV can tend to underdo the energy though and especially has recently with the early season risks its been quite low compared to some of the other models. 

Saturation looks high though. That'll likely keep the lightning down to a minimum unless it trends down. Lots of potential moisture for flash flooding on the other hand. 

Buoyancy is still largely varied on the models. Forcing could well turn out to be anything if these are anything to go by. 

[Wade]

I am in the middle of that lot there spreading north east, hopefully I'll get my first thunderstorm of 2024 if the ingredients are all there added with a good ole bit of Irish luck 

[TJS1998Tom]

 Wade If it pushes up to Lincolnshire which is usually a hot spot then it could be perfect timing as I finish work at 4pm

[Wade]

 TJS1998Tom I've just got back from visiting my grandparents from Scotland so a thunderstorm would be a good welcome back but I noticed storm force beka had a storm in her location at the only time she was away. That happened to me once, that's life though isn't it. 

[Eagle Eye]

I'm not convinced of the moderate and wanted to go with the slight with AOI risk that we made but Jay went with the moderate so here's today's risk.

Convective Outlook️ 

50+ J/KG of 3CAPE could form over the SE during the evening hours along an envelope of deeper moisture pushed by a forcing lobe north of the original one over France. This could help push a few thunderstorms to form mainly in the SE but perhaps in areas further north along the east and areas a bit further west along the south coast. Also, an area of storms could form mostly in the Irish Sea but hit the Welsh and southeastern Irish coasts.

 

The further south this forced band in the SE or eastern part of the UK is, the worse it is, as the France storms expand north, those storms could become part of some sort of MCS or cluster of cells and weaken as they could become constructive momentum feeders for the French cells. Also, it's not guarantee that the forcing will be enough to get meaningful CAPE together and instead, we'll be relying on initiation further west over northern France pushing into the SE, which is looking like the most likely scenario on the models and it's half and half as to whether the SE and eastern parts get anything. Perhaps they could survive the channel because they are likely to be the only storms or the day and so the CAPE hasn't been taken up, or they could force new cells to form ahead or along with them on the south coast into a cluster that the shearing favours.

 

There's a small chance of a tornado within this given the low-level shearing but the energy is likely too lackluster to really help. That also likely means hail would be kept to quite small.

 

No matter where there storms form, 500+ J/KG of MUCAPE appears likely and it could reach up to even just a bit more than 1000 J/KG of MUCAPE mostly held beyond a surface inversion, which if that holds, could help stop surface storms from forming in France and go immideately to elevated storms, likely to be less severe, but bring a higher risk of lightning for eastern parts of the country, mainly the SE.

 

DCAPE could be enough for some meaningful but less than severe wind gusts with these. However, the energy is what looks to keep it sub severe, it doesn't seem to reach the 500?+ J/KG of DCAPE for downdraft to be meaningful enough for severe wind gusts from the potential storms.

 

Lightning could be fairly frequent from these especially as they appear to miss the highest of the saturation that is held in the lower levels. However, there appears to be still some fairly strong mid-level saturation for the storm to work through along with a lot of moisture to slightly dampen lightning risk and increasing the small flash flooding risk.

 

The WRF is especially strong with all this, giving some areas 1000+ J/KG of MUCAPE with a hooked low-level where just enough low-lebel energy is present, beating the surface inversion but over the SE, for a small tornadic risk.

 

If surface based energy can properly be forced as the WRF suggests over the SE then we could well see very frequent lightning and storms with severe capabilities but only realltr the WRF is that severe with this energy its showing. However, it's got many previous events of similar nature right whilst other models have struggled, so it's something to keep an eye on.

 

Buoyancy shouldn't bet too much of an issue, it's kind of just there, however that's for the models where the forcing band is evident. If it isn't then the lift in the atmosphere probably won't be enough anyway and there'd be too much opposing the storms. Hence why it's such a difficult forecast for eastern parts of the country shown by all the model differences that are still very much evident.

 

Just enough energy of about 300+ J/KG of MUCAPE over the SE Irish and Welsh coastal risk could allow for a band of storms to form into a cluster quickly into the late evening, perhaps staying in the Irish Sea but could hit coasts as rit moves north. There's good model agreement that these should form though.

Here's the risk that I wanted to go with. But we'll see, I was more worried about the fact that it's very 50/50 on the models so I don't think a moderate would be an accurate representation of the risk. 

[Robert1981]

 Eagle Eye could be an interesting day

[Jamie M]

Today does seem to hold some merit at least for the far SE for the potential of some thundery activity into the evening.

Shear profiles from AROME do seem to suggest the possibility of organised convection developing in the far SE with a low chance of any storm developing supercellular characteristics with it. It seems more likely that this will happen in northern France due to the 1500 J/kg of MUCAPE being available vs the 600/700 available in the SE. The abundance of potential convection developing in the SE does make me feel it's pretty unlikely unless one of the storms scoops up everything left in its environment. 

AROME did seem to play with the idea of a supercell developing in northern France on its 12z run yesterday with a storm that deviated to the right of its mean wind.

Theta-E values are also highest in the far SE which seems to indicate to me at least that there is where most of the thundery activity will be even if convection does develop further west. All that being said however I still wouldn't put the chances of any thunderstorms developing at anything other than a slight chance considering conditions look MUCH better across the pond in France. 

[Eagle Eye]

 Jamie M Agreed, we are once again looking at France and hoping they don't sort of take any potential energy for our storms as they often do, hence why I only wanted a slight risk. There just too much going against it at the moment. 

[Southern Storm]

 Eagle Eye it looks like the first of the storms had developed over France and like you said, I hope that all the energy doesn't get used up before reaching the southeast! Good luck for later  

[Eagle Eye]

 Southern Storm Thank you, just a case of waiting to see what happens now. Forget the models and hope for the best, blue skies here though and some accas on the sky are good signs. 

[Thunders]

just got back from renovating new  house, quite happy to see a risk for us in kent/sussex. hopefully it aint a bust this time tho.

 Eagle Eye same but it is also kinda hazy in the sky ( idk the proper word really )

[Southern Storm]

Slate grey here, and has been since around 12pm, the UKv looks like it's already a little off with the amount of rain pushing out of France towards CS England, so all bets are off

[Eagle Eye]

The storm that's supposed to be over Amiens by now hasn't formed, potentially a good sign. Seems to be running a little late with everything though. 

[Ryan H]

 Jamie M Seems we may had a spring thunderstorm in parts of England that could become a Supercell.

[Thunderspotter]

It's been a few days lol

I'm guessing that the CS haven't really got a good chance today - just a band of heavy rain, so I'm going to focus on some revision and if anything happens I'll be sure to come on and have a chat.

Good luck to everyone in the SE, hoping to see some lively stuff this evening!