Storms and convective discussion - 1st April 2021 onwards

[ChannelThunder]

18 hours ago, Flash bang flash bang etc said:

Looks quite convective this evening around the central south. Some lovely little cauliflower tops, can’t wait for the season to start

Yeah, the late PM sun was shining through a slightly hazy bank of clumpy AC here, making for a classic summery/stormy looking scene. There was some nice Congestus around in the afternoon too before most of it flattened out 

[ChannelThunder]

Finally, a little bit of convective activity is possible in this extremely quiet month. 

Cold air aloft on Wednesday along with slack low pressure and surface heating could give some hefty showers through the afternoon. Some thunder from these seems possible given the time of year. Chief areas of interest would seem to be south and west of London, but different models show different locations for most of the precip.

Later in the week and over the weekend, again a slack set-up could lead to slow-moving downpours developing. 

 

Nice to have a few convective breadcrumbs on the horizon at last!

Edited April 26, 2021 by Lance M

[Jamie M]

Nice little storm offshore near Weymouth this morning.

[Guest]

8 minutes ago, Jamie M said:

Nice little storm offshore near Weymouth this morning.

It’s amazing how the form over the sea with SST’s at 9c yet fall apart during mid summer....but that’s really quite a pokey little storm. 

[Eagle Eye]

We can finally start looking past Winter now that we are having proper April showers today, expecting the rotation to leave me with some later on as well, unfortunately might be in Lesson.

The centre of the rotating system seems to be East of London. 

You can see the full extent of the Storm with a possible wag of the Tail up through London. 

[ChannelThunder]

That's indeed a fair bit of lightning for so early in the morning and so early in the season. Has to have been elevated, right? Cloud bases in general seem high over the last 12-24 hours, at least around these parts!

 

Edit: Dan's outlook for today gives more detail on that storm: http://www.convectiveweather.co.uk/forecast.php?date=2021-04-28

 

Edited April 28, 2021 by Lance M

[Eagle Eye]

24 minutes ago, Lance M said:

That's indeed a fair bit of lightning for so early in the morning and so early in the season. Has to have been elevated, right? Cloud bases in general seem high over the last 12-24 hours, at least around these parts!

 

Edit: Dan's outlook for today gives more detail on that storm: http://www.convectiveweather.co.uk/forecast.php?date=2021-04-28

 

I imagine your right finally getting some April weather and surviving the channel better than last year.

[chapmanslade]

2 hours ago, Alderc said:

It’s amazing how the form over the sea with SST’s at 9c yet fall apart during mid summer....but that’s really quite a pokey little storm. 

But with 850hPa temperatures of below zero there is plenty of thermal gradient over 9C SST to get things moving. Very different in the summer when the SST is lower than the air above.

[chapmanslade]

24 minutes ago, Eagle Eye said:

I imagine your right finally getting some April weather and surviving the channel better than last year.

Surviving ? Initiating more like. This is more of a winter setup with relatively warm SST's below cold upper air

[Eagle Eye]

 

4 minutes ago, chapmanslade said:

Surviving ? Initiating more like. This is more of a winter setup with relatively warm SST's below cold upper air

Okay, well this does not feel like April.

[Eagle Eye]

Anybody remember last April when @Thunder and Lightningcaught the beauty just behind his house, that was April 12th around that date this Year it was snowing for me.

 

[Eagle Eye]

It will never happen but these jet stream's "could" make for a big plume.

[ChannelThunder]

7 minutes ago, Eagle Eye said:

It will never happen but these jet stream's "could" make for a big plume.

It'd be a step in the right direction, but the jet would need to be a good few hundred miles further west than that. As you'll see on the corresponding pressure charts for that date on the same model run, that would take any low pressure systems up out of France and to the east of the UK, so any unstable air would be far to the east (Germany etc) and we'd be on the 'cold side' of the jet in more stable conditions.

[Eagle Eye]

38 minutes ago, Lance M said:

It'd be a step in the right direction, but the jet would need to be a good few hundred miles further west than that. As you'll see on the corresponding pressure charts for that date on the same model run, that would take any low pressure systems up out of France and to the east of the UK, so any unstable air would be far to the east (Germany etc) and we'd be on the 'cold side' of the jet in more stable conditions.

Like you said though, a step in the right direction, looking at the Jet Stream now we are slowly getting there.

[Eagle Eye]

Forecast has been issued, looks like the main burst has definitely cleared by now and just some sporadic strikes to come. Looks like high CAPE this afternoon though so especially further South has a chance of a few weak thunderstorms.

Convective Weather

WWW.CONVECTIVEWEATHER.CO.UK

---

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

Day 1 Convective Outlook: Wed 28 Apr 2021   

Day 1 Convective Outlook

VALID 06:00 UTC Wed 28 Apr 2021 - 05:59 UTC Thu 29 Apr 2021

ISSUED 06:44 UTC Wed 28 Apr 2021

ISSUED BY: Dan

An active cluster of thunderstorms are ongoing over Lyme Bay, in close proximity to the low centre / convergence and on the leading edge of a marked dry intrusion. This feature could potentially persist for a few hours before eventually weakening. Either way, an upper low covers southern Britain during Wednesday with forcing aloft encouraging areas of showery rain to develop, some perhaps capable of producing isolated lightning strikes.

Depending on sufficient cloud breaks, surface heating over southern counties of England (West Sussex across to Devon) could yield in excess of 500 J/kg CAPE by the afternoon hours in an environment with weak shear but steep mid-level lapse rates. Low-level convergence may aid the development of heavy showers and a few weak thunderstorms in this area, although given the saturated profiles and weak shear, pulse-type mode is most likely (lightning risk 15-20%). Some small hail may be possible, and locally high rainfall totals / localised flooding given the slow movement. Reluctant to issue a SLGT at this stage due to uncertainty over extent of cloud breaks/surface heating - but an expansion to the SLGT may be required if confidence improves.

[Mapantz]

It certainly feels and looks like a Summer thundery day here. Convergence taking place!

[Frosty hollows]

41 minutes ago, Mapantz said:

It certainly feels and looks like a Summer thundery day here. Convergence taking place!

You might be in luck

[Guest]

Very heavy hail shower now in Poole.

[Mapantz]

13 minutes ago, Frosty hollows said:

You might be in luck

Just heard a faint rumble and detected a strike on my wx station.

[Guest]

Loud storm over Poole! 

[Mapantz]

A cracker of a shower here. Most welcome.

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Thu 29 Apr 2021 - 05:59 UTC Fri 30 Apr 2021

ISSUED 06:46 UTC Thu 29 Apr 2021

ISSUED BY: Dan

A broad upper trough covers much of northern and western Europe, the associated cold pool in conjunction with diurnal heating yielding a couple hundred J/kg CAPE. While scattered showers will become more numerous for the afternoon and evening hours, the depth of convection for the most part will be quite restricted and so generally the risk of lightning is barely 5% in most areas. However, within the base of the upper trough steeper mid-level lapse rates will exist over Ireland, with CAPE up to 400 J/kg locally - and so overall Ireland has a greater risk of a few isolated lightning strikes (10%). Small hail will likely accompany many of the showers. The generally slack surface flow and resultant low-level convergence combined with steep low-level lapse rates could allow a couple of funnel clouds to develop - more especially in W / NW Ireland.

http://convectiveweather.co.uk/forecast.php?date=2021-04-29

 

[matty40s]

Some interesting shapes going up towards Rugby.

[BlueHedgehog074]

Had a heavy wet hail shower a few miles to the East of Solihull, which passed through here around 2pm. May have even been the odd isolated sleety blob or two mixed in with the hail at some point as it reached it’s heaviest.

[matty40s]

Got hailed and graupelled on an hour ago just before the front wheel came off the John Deere!!

 

The large shower just North of Daventry is looking very interesting...

Edited April 29, 2021 by matty40s