Storms and Convective Discussion - 20th April 2019 onwards

[Another Kent clipper]

2 hours ago, ChezWeather said:

I have a feeling that i'll be suffering from a severe lack of sleep next week, no time off work and likely pulling all-nighters on Sunday and Monday 

Plume rules.  At work: "why are you so tired"... "Erm I was checking the radar.  At 12, 2, 4, and 6am.  Contemplated going out for a look when I was within 100 miles of sferics but then I fell asleep"

[Thunder and Lightning]

latest GFS seems to favour Thursday most with shear and also looks like it wants heat to last further into the weekend.

[Chris.R]

 WRF not that interested in anything here on Sunday night. Was looking forward to that, hopefully it picks it up. Will have a better idea when the warnings are updated later. 

[Marko1690]

Was watchin the met office forecasters expression when he is describing the potency of the storms that are forecast, could we see a once in a lifetime event this week?

[James1979]

11 minutes ago, Marko1690 said:

Was watchin the met office forecasters expression when he is describing the potency of the storms that are forecast, could we see a once in a lifetime event this week?

Would be a nice way to mark the 25th anniversary of the best storm I've personally ever seen but I think (in my area at least (what's new)) that will remain the once in lifetime event for me. 

Edited June 22, 2019 by James1979

[James1979]

Does anyone know if that footage from the Brighton livecam the other night gets recorded anywhere?  Reason being is there was a point whilst watching that that I saw 2 distinct balls of light (very small) shoot off to the left of the image just after a strike and disappear/fizzle out - was seriously wondering if I witnessed ball lightning of some sort - did anyone else see this? I know ball lightning definitely exists as my mum witnessed an extreme event in a tall building in London back in the 50's - green balls of varying sizes fizzing around and exploding outside the window during a violent storm but she never wanted to tell anyone else for fear of being labelled a liar! I find it hard to believe that no one has successfully filmed anything like this still.  Anyway, I digress... 

Edited June 22, 2019 by James1979

[Met4Cast]

High res models picking up on Sundays storm potential now. First "wave" of storms develops across Wales/NW England during Sunday afternoon though it's likely lightning will be fairly sporadic due to a rather capped atmosphere, heavy rain more the issue during the afternoon.  A second wave of more extensive/likely more severe storms moves north across SW England into Wales during the evening, likely moving NW into the Midlands, N England & NE England overnight into Monday, though that's just out of model range. 

Could be a few MCS storms develop within that, torrential rain, hail & flash flooding. Lightning likely to be more elevated so quiet storms rather than the BOOOOOM type storms. Cloud tops aren't forecast to be particularly cold unfortunately 

The steepest lapse rates likely not moving North until after midnight. Strong deep layer shear may allow for some locally severe storms.

Edited June 22, 2019 by Met4Cast

[Harry]

There’s been some fairly big changes to the GFS over the past 24 hours, wiping away much of the storm potential for the weekend and early part of next week (except for some northern/western parts but with sensible levels of instability and some modest MUCAPE across the south Sunday night). The WRF-NMM seems to agree, although incursions of instability may still affect parts of the far SE at times.

That is not to say it won’t be hotting up, it seems that subtle model changes merely delay the arrival of the very humid and unstable air until later (but there is a surge from say Wednesday into Saturday). 

I’ve pasted the FAX charts for Sunday, Monday and Tuesday night and the MUCAPE charts which demonstrate the above (first two WRF-NMM, latter GFS as Tuesday 00z not in range).

It does suggest Sunday night could be more heavy perhaps thundery rain. Monday night sees a trough straddling eastern England which could provide focal point for torrential showers or storms but instability (as referred to above) as been scaled right back. Tuesday night sees high MUCAPE brush the far SE while the FAX chart points towards a secondary or thundery low moving N or NE from Spain across France. Any slight adjustments (as we have seen) could make a big difference in terms of instability/storms but the first part of next week has certainly shifted somewhat away from stormageddon, although torrential rain/showers still very much in the offing.

Edited June 22, 2019 by Harry

[Mizzle]

30 minutes ago, James1979 said:

Does anyone know if that footage from the Brighton livecam the other night gets recorded anywhere?  Reason being is there was a point whilst watching that that I saw 2 distinct balls of light (very small) shoot off to the left of the image just after a strike and disappear/fizzle out - was seriously wondering if I witnessed ball lightning of some sort - did anyone else see this? I know ball lightning definitely exists as my mum witnessed an extreme event in a tall building in London back in the 50's - green balls of varying sizes fizzing around and exploding outside the window during a violent storm but she never wanted to tell anyone else for fear of being labelled a liar! I find it hard to believe that no one has successfully filmed anything like this still.  Anyway, I digress... 

Would be interested to know where in London. My father in law also tells me a about the ball lightning he saw in London as a child - 1950s.

[ChezWeather]

http://www.convectiveweather.co.uk/forecast.php?date=2019-06-23

Day 2 Convective Outlook

VALID 06:00 UTC Sun 23 Jun 2019 - 05:59 UTC Mon 24 Jun 2019

ISSUED 07:50 UTC Sat 22 Jun 2019

ISSUED BY: Dan

Longwave trough will linger over the Atlantic close to western Europe on Sunday, the southerly flow on its forward flank encouraging advection of an elevated mixed layer (EML) from the Spanish Plateau towards southern Britain by Sunday night.

Ahead of this, an isolated heavy shower / thunderstorm is possible during Sunday afternoon / early evening in a zone from Cen S England / S + W Midlands / Wales. However, despite profiles exhibiting reasonable speed and directional shear to aid organisation, one or more warm noses may significantly restrict cloud depth and so the risk of lightning is treated with quite a low probability for now. In fact it is probably more likely that outbreaks of largely dynamic rain will be falling from medium-level cloud over Wales / Midlands, associated with the warm front slowly lifting northward. A few showers are also likely in N and W Scotland, but with very little lightning expected.

Main thunderstorm interest is during Sunday night. By Sunday evening, frontal rain will likely already be affecting parts of SW England, Wales, W Midlands and Ireland - behind which advection of an increasingly warm, moist low-level airmass will occur during the overnight hours. A lead shortwave impulse in the strong southerly flow aloft will aid ascent, coupled with isentropic upglide as the EML arrives. MLCAPE values of 500-1,000 J/kg are expected, this instability being released through the course of the night. 

With time, scattered elevated thunderstorms - initially over parts of SW England / S Wales / Celtic Sea / S Ireland - will become more numerous and drift north/northwestwards as the night progresses. Strong deep layer shear should help thunderstorm complexes to grow upscale into an MCS (mesoscale convective system), as coverage continues to expand eastwards across northern England during the early hours of Monday. Given the magnitude of CAPE/shear, lightning will be very frequent at times, accompanied by the threat of hail, gusty winds and locally very heavy rain.

This extended outlook provides an overview of the most likely forecast evolution during this forecast period - however destabilising plume events are often fraught with uncertainty, and it is likely certain aspects of the forecast will change as the event draws closer. However, provided guidance continues to remain relatively consistent, upgrades to higher threat levels are possible in future outlooks.

[Mapantz]

1 hour ago, Chris.R said:

 WRF not that interested in anything here on Sunday night. Was looking forward to that, hopefully it picks it up. Will have a better idea when the warnings are updated later. 

UKV is, and storms developing during the early hours of Monday.

Edited June 22, 2019 by Mapantz

[Chris.R]

 Looks like Sunday night is still on then. Just waiting for 6Z WRF  raw data. Love convectiveweather‘s forecast. 

[Chris.R]

3 minutes ago, Mapantz said:

UKV is, and storms developing during the early hours of Monday.

Thanks

[LightningLover]

1 hour ago, James1979 said:

Does anyone know if that footage from the Brighton livecam the other night gets recorded anywhere?  Reason being is there was a point whilst watching that that I saw 2 distinct balls of light (very small) shoot off to the left of the image just after a strike and disappear/fizzle out - was seriously wondering if I witnessed ball lightning of some sort - did anyone else see this? I know ball lightning definitely exists as my mum witnessed an extreme event in a tall building in London back in the 50's - green balls of varying sizes fizzing around and exploding outside the window during a violent storm but she never wanted to tell anyone else for fear of being labelled a liar! I find it hard to believe that no one has successfully filmed anything like this still.  Anyway, I digress... 

It's funny that you say that; One of my friends from school, who lives in Ticehurst, says he saw something similar. He described it as 'A bright blue ball that raced across our field after a big bolt of lightning'. So he's not alone, then!

[ChezWeather]

Plenty of support from the precip models for storms on Sunday night/Mon morning

EURO4 and AROME currently not in range unfortunately 

GFS

ICON

APERGE shows nothing until 9am Monday

HIRLAM only out to midnight at the moment

Netweather MR going way further West

 

[StormChaseUK]

Looks like 2 rounds of convection this week

First round starting tomorrow as low trundles in, then heat pushes it back west , before it tries to come back in next week.  Similar setup that gave Finland 33C or so a month ago, but back then we were the ground zero for the low. This time we get to enjoy the southern blast instead due to it being out west.  

Then later in week as the heat builds 

Both forms will be elevated I think, homegrown elevated. We are either used to surface based homegrown storms or elevated from France. So will make a nice change to form our own, (last good example July 2014) where West Midlands had quite potent elevated storms forming 1am - 4am , dry no rain but dramatic lightning, 2 nights in a row.  Accas visible from 10pm onwards.

[Mapantz]

31 minutes ago, StormChaseUK said:

dry no rain

Not true. Torrential downpours with hail are likely.

[StormChaseUK]

1 minute ago, Mapantz said:

Not true. Torrential downpours with hail are likely.

Not in 2014, I stayed up all night watching the lightning. Was no rain .    Will be rain this week but elevated in nature, but I wouldn't be suprised to see people have storms without any rain too.

[Mapantz]

5 minutes ago, StormChaseUK said:

I wouldn't be suprised to see people have storms without any rain too.

Most likely due to the fact that they'll be on the periphery of any storm (s)

In favoured areas on Sunday eve, an inch of rain in under an hour is quite feasible.

[Flash bang flash bang etc]

43 minutes ago, StormChaseUK said:

Looks like 2 rounds of convection this week

First round starting tomorrow as low trundles in, then heat pushes it back west , before it tries to come back in next week.  Similar setup that gave Finland 33C or so a month ago, but back then we were the ground zero for the low. This time we get to enjoy the southern blast instead due to it being out west.  

Then later in week as the heat builds 

Both forms will be elevated I think, homegrown elevated. We are either used to surface based homegrown storms or elevated from France. So will make a nice change to form our own, (last good example July 2014) where West Midlands had quite potent elevated storms forming 1am - 4am , dry no rain but dramatic lightning, 2 nights in a row.  Accas visible from 10pm onwards.

Didn’t that one form over the channel?

[richep]

Met office removed warning for the south tomorrow night.

[Mapantz]

It looks like the Met Office feel as the overall thunderstorm risk has reduced and therefore the warning has been restricted to parts of North Wales and Northern England on Sunday night. This ties in with the UKV model.

[Thunder and Lightning]

Storms aren't looking that exciting any more. We all kind of knew they wouldn't be as bad as the models originally said it would be, still hoping for some potential though.

[StormChaseUK]

8 minutes ago, Flash bang flash bang etc said:

Didn’t that one form over the channel?

I will find the archive charts, the 2014 July storms, formed over Hereford/Brecon location then drifted up over the Welsh Marches to Shrewsbury/Telford. 

[Wilxy]

3 minutes ago, Mapantz said:

It looks like the Met Office feel as the overall thunderstorm risk has reduced and therefore the warning has been restricted to parts of North Wales and Northern England on Sunday night. This ties in with the UKV model.

Isn't this related to the surface based storms, I thought it still looked good for elevated storms sunday night into monday