Storms and Convective discussion - 20th March 2023 onwards

[Woodboss]

On 10/05/2023 at 17:59, Superstormuk said:

Some photos from just ouside Maidenhead yesterday evening. Some really cool structures and striations. 

Great shots these are! This is a particularly interesting looking storm too. The third photo looks to me like a half decent attempt at a wall cloud looking at the structure of this!

[Rufus Butterfield]

YouTube’s now processed the video of the storm (5th May) to HD so I’ll share it here.

 

 

[Raindrops]

2 hours ago, Rufus Butterfield said:

YouTube’s now processed the video of the storm (5th May) to HD so I’ll share it here.

 

 

You cleaned the camera in the nick of time, the reversed square root symbol lightning was awesome, you could almost see it coming up from the ground.

[Eagle Eye]

Decent looking mammatus or something earlier and there were 1 or 2 bits of bubbly cumulus as well.

[Rufus Butterfield]

2 hours ago, Raindrops said:

You cleaned the camera in the nick of time, the reversed square root symbol lightning was awesome, you could almost see it coming up from the ground.

Next step is to actually use my tripod for once…

[fromthecab]

[Eagle Eye]

I like the 4:3 higher resolution mode on my phone.

[Eagle Eye]

Convective Outlook ️

 

Surface based showers will develop across N/E England, Scotland & Ireland in response to surface based heating.

 

A low pressure will develop across Scotland enhancing the activity of shower development.

[summer blizzard]

Any update, radar looks a bit pitiful. 

[WeatherArc]

Confidence seems to be slowly increasing in somewhat robust thunderstorm development at the end of the month. Main days of focus seem to be Saturday 27th-Monday 29th.

Low to mid 20s temps combined with 15+ degree dewpoints should yield some modest instability values, current modelling suggests the highest values could range from 500-2000 j/kg of CAPE

However the strongest cape values are likely being limited by those weak mid-level lapse rates. Weak bulk shear will also limit storm longevity.

Some fairly nice profiles here, nice to see MLcape above 1000 and 3cape above 75. Absolutely no SRH though. Due to the lack of low/mid layer shear i suspect any storms will struggle with a wind/hail threat. Although the strong elevated instability will likely make them good lightning producers.

Some good GEFS support for this.

The GFS does seem to have some run to run differences though. We'll see what the euro thinks when it comes into range

06Z

12z

[Eagle Eye]

1 hour ago, WeatherArc said:

Confidence seems to be slowly increasing in somewhat robust thunderstorm development at the end of the month. Main days of focus seem to be Saturday 27th-Monday 29th.

Low to mid 20s temps combined with 15+ degree dewpoints should yield some modest instability values, current modelling suggests the highest values could range from 500-2000 j/kg of CAPE

However the strongest cape values are likely being limited by those weak mid-level lapse rates. Weak bulk shear will also limit storm longevity.

Some fairly nice profiles here, nice to see MLcape above 1000 and 3cape above 75. Absolutely no SRH though. Due to the lack of low/mid layer shear i suspect any storms will struggle with a wind/hail threat. Although the strong elevated instability will likely make them good lightning producers.

Some good GEFS support for this.

The GFS does seem to have some run to run differences though. We'll see what the euro thinks when it comes into range

06Z

12z

My initial thoughts.

1- Saturation is changing quite a lot in those suggesting localised strong thunderstorms more likely than an upscaling event.

2 - Shearing and forcing will change easily with this event. Notice the cut off surface low with the shearing parallel to either side of it (shearing parallel to cold fronts and with rapid cyclogenesis and front genesis I imagine thst the gravity waves sent out which the GFS won't have picked up on would be rather strong which could enhance PV and bouyant activity compared to what those soundings suggest. Not entirely sure whether or not it can change shearing in an area. I imagine the change of the flow in a wave-like pattern if strong enough could potentially do that.

3 - This will change of course.

4 -Hail growth depends on weak low-level shearing and strong deep-layer shearing with cold upper air in place. Typically you see a C shaped hodograph with the deep-layer shear relative to relative storm inflow and you've kind of got that on the second sounding but the weak lapse-rates significantly decrease that. So definitely no large hail but I don't think it's non hail supportive. Though as I was talking to Nick Silkstone of the Met Office a few weeks ago or so, he did mention that The large hail support with what I just mentioned along with height of freezing zone and the amount of CAPE below 0 is mainly used for Supercells and there's not much research into non-Supercellular large-hail. For large-hail in Supercells, I suspect that you want an inflow jet (rear inflow jet potentially, E.G giant hail with a squall line is plausible) along with strong parcel bouyancy with cold low to the surface. If the storm can latch onto as much of the cold air as possible (e.g. elevated) and with little to none below cloud layer shearing then I could see large hail forming from non-Supercells.

Edited May 16, 2023 by Eagle Eye

[Eagle Eye]

Convective Outlook ️

Widespread heavy showers will develop in response to surface heating. There is potential for one of these showers to produce the odd  isolated lightning strike.

Convergence zones may develop where Sea breezes occur, which will force the showers to develop.

Edited May 17, 2023 by Eagle Eye

[Guest]

Absolute gunshot thunder here in southern Spain, huge defeating strikes every 15-20 seconds now. 

[Thunders]

32 minutes ago, Alderc said:

Absolute gunshot thunder here in southern Spain, huge defeating strikes every 15-20 seconds now. 

Southern spains got a few storm rn

[Metwatch]

53 minutes ago, Alderc said:

Absolute gunshot thunder here in southern Spain, huge defeating strikes every 15-20 seconds now. 

 

Should ideally be saying this in European convective thread, (feel free for someone to move the posts there) but looks like some convergence about leading to some potent storms there.

[Flash bang flash bang etc]

Meanwhile here in the southern U.K. I spy pileus

[Andrew Hurcomb]

Edited May 18, 2023 by Andrew Hurcomb
Sorry wrong board

[Flash bang flash bang etc]

Quick question: which nylon is best for sewing on sleeves?

Just I see a lot of people using the wrong thread today

[Mapantz]

Just had a quick scout of the UKV.. Could be interesting tomorrow afternoon?!

[CoventryWeather]

45 minutes ago, Mapantz said:

Just had a quick scout of the UKV.. Could be interesting tomorrow afternoon?!

Seems it - Arome and UKV showing a long convergence from the Humber to the Bristol Channel. Might be some issues with saturation I assume - don't know if the experts can help with that one!! 

[Mapantz]

Very 'plumey' looking skies here this evening.

[WeatherArc]

Update on the potential for some strong thunderstorms at the end of the year. GFS guidance still all over the place, the potential is there but havent got as much confidence in anything as of this post so take all the stuff below with a pinch of salt.

The 06Z GFS run today showed another incredibly unstable environment with temps in the low to mid 20s and dewpoints nearly breaching 20°C creating a large amount of instability being modeled across the central and south of the country with cape values exceeding 2000 j/kg in someparts.

This could lead to some strong to potentially low end severe thunderstorms developing across the area. Since my earlier post lapse rates, wind shear and SRH have slightly increased.

Very nice profiles here, shear still on marginal side but definitely a hail threat in some of the stronger updrafts, also possibly the potential for a weak supercell, bulk shear is still rather marginal but there is a decent amount of veering in the atmosphere. Small but nicely shaped hooked hodographs and that strong instability aloft will likely help. A small chance of a very weak tornado but it's difficult to forecast right now.

Regardless of the wind/hail/weak tornado threat these storms will likely be good lightning producers owing to that instability and especially if lapse rates keep increasing. 

However, it's still difficult to say whether this solution will win out in the models. Although i'm glad this keeps showing up on occasional runs the GFS general run to run consistency is very low.

06Z 

12Z

GEFS not much better, seems like it's stuck between producing this surface low or just keeping high pressure on top of us

Even if high pressure wins out i wouldn't be too annoyed, its only May and im getting the feeling we are in for a good year of storms.

On 16/05/2023 at 21:25, Eagle Eye said:

My initial thoughts.

1- Saturation is changing quite a lot in those suggesting localised strong thunderstorms more likely than an upscaling event.

2 - Shearing and forcing will change easily with this event. Notice the cut off surface low with the shearing parallel to either side of it (shearing parallel to cold fronts and with rapid cyclogenesis and front genesis I imagine thst the gravity waves sent out which the GFS won't have picked up on would be rather strong which could enhance PV and bouyant activity compared to what those soundings suggest. Not entirely sure whether or not it can change shearing in an area. I imagine the change of the flow in a wave-like pattern if strong enough could potentially do that.

3 - This will change of course.

4 -Hail growth depends on weak low-level shearing and strong deep-layer shearing with cold upper air in place. Typically you see a C shaped hodograph with the deep-layer shear relative to relative storm inflow and you've kind of got that on the second sounding but the weak lapse-rates significantly decrease that. So definitely no large hail but I don't think it's non hail supportive. Though as I was talking to Nick Silkstone of the Met Office a few weeks ago or so, he did mention that The large hail support with what I just mentioned along with height of freezing zone and the amount of CAPE below 0 is mainly used for Supercells and there's not much research into non-Supercellular large-hail. For large-hail in Supercells, I suspect that you want an inflow jet (rear inflow jet potentially, E.G giant hail with a squall line is plausible) along with strong parcel bouyancy with cold low to the surface. If the storm can latch onto as much of the cold air as possible (e.g. elevated) and with little to none below cloud layer shearing then I could see large hail forming from non-Supercells.

Really interesting read, I totally agree with you especially with that non-supercellular small hail threat and potential gravity waves.

I'm still quite new to meteorology so apologies if i make any mistakes especially regarding the skew T plots.

 

 

Edited May 18, 2023 by WeatherArc

[Eagle Eye]

16 minutes ago, WeatherArc said:

 

Really interesting read, I totally agree with you especially with that non-supercellular small hail threat and potential gravity waves.

I'm still quite new to meteorology so apologies if i make any mistakes especially regarding the skew T plots.

 

 

Thank you and don't worry, very few people understand skew-T plots that well and it took me years to work out properly. Over the summer I'm going to attempt to compile a report in-detail of non-Supercellular large-hail to get a better understanding of forecasting it in the future but Ive got my GCSE's first.

Tomorrow's forecast as well. P.S. I had no involvement in the production of that map .

Convective Outlook ️

Convergence zones will form during Friday allowing heavy & intense showers to develop. Alongside with these Showers brings a fair amount of instability (400-800J/KJ CAPE) therefore a thunderstorm or 2 can be expected.

Low-end SLGHT risk.

I didn't write the discussion either for that but I do most days and I'm still part of the group just didn't have the time tonight otherwise you would've seen a few paragraphs. I suspect convection depth and saturation may be a potentially bust factor but haven't looked too much into it myself.

Edited May 18, 2023 by Eagle Eye

[The Tall Weatherman]

Dan’s forecast for today ️️

Convective Weather

WWW.CONVECTIVEWEATHER.CO.UK

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Forecasting thunderstorms and severe convective weather across the British Isles and Ireland for up to the next 5 days.

 

[CoventryWeather]

Cold front looks more active than modelled - hopefully the cloud associated with it can break up as forecasted.