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Storms and Convective discussion- 15th August onwards


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34 minutes ago, StormLoser said:

Argh - locked myself out of my account!  It's actually probably my Gurgle Chrome (Win 10). It won't access the site - going at a total crawl. I didn't even know if my message got posted.

It's probably the Chrome cache. MS Edge works fine here. Please don't worry about it. Thanks!

Update: yep - Chrome cache. All good now.

Ok great. 

To answer your question, looks like being somewhere around 5-6pm ish. 

sqall.png

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Didn’t know we was expecting an avalanche today 🤔

Stonking day for storms. Had two cells with continuous thunder [but mostly no visible lightning again]. Here's some pictures of one storm that I tracked as it progressed up the M11 which produced some

Am enjoying a weekend away 60 miles S of Prague in the pretty town of Písek, the storm front that came in this evening was dramatic! 

Posted Images

image.thumb.png.fc6a17160d5d94c4ffd5068f1b4d29ac.png image.thumb.png.15a08ae46e1663bb877d085af34d8165.png

AROME 0z vs 6z

Improvement on the structure as a whole. Although, my pessimism tells me that the first one is more likely.

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49 minutes ago, Zak M said:

I've actually never received thunder from a squall line before. Could tomorrow be the day?

I have, a few years back now. Was a very strong one with very heavy rain and the wind was scary. 

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52 minutes ago, Zak M said:

I've actually never received thunder from a squall line before. Could tomorrow be the day?

Had one a few years ago here which had thunder, it also brought a few trees down nearby. 

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1 hour ago, Zak M said:

I've actually never received thunder from a squall line before. Could tomorrow be the day?

Squall lines are very rare here now but in the past we used to get them with lightning hail and strong winds.

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Day 1 Convective Outlook

VALID 06:00 UTC Sat 24 Oct 2020 - 05:59 UTC Sun 25 Oct 2020

ISSUED 07:46 UTC Sat 24 Oct 2020

ISSUED BY: Dan

A cold front will migrate steadily eastwards across Britain on Saturday, with a marked thermal gradient and wind veer. This, coupled with a strongly-sheared environment suggests scope for line segments to develop, increasingly so from mid afternoon into the evening hours across parts of central, southern and eastern England. This squall line, perhaps broken at times, will bring the threat of brief periods of torrential rain and strong gusts of wind, including the potential for one or two isolated tornadoes. Much of the time the embedded convection will likely be fairly shallow in height, suggesting a low risk of lightning (5-10% chance), however there may be scope for deeper convection to occur along the squall line across S / SE England and into East Anglia later in the day which would increase the potential for a few lightning strikes (10-15%).

Immediately behind the cold front, guidance suggests the potential for another area of showery rain, with embedded convection on its southern/eastern flank, to swing northeastwards across parts of England and Wales during the evening hours. The strongest convection on the southeast side of this cluster could produce a corridor of very strong winds, most likely across parts of SW England / SE Wales and into the Midlands. An isolated tornado is also not ruled out from this feature either.

 

A SVR has been issued for Saturday afternoon/evening for the potential for locally damaging winds as the squall line moves through along the cold front, and also with any post-frontal convection during the evening hours, plus the risk of an isolated tornado.

 

Throughout Saturday across western Scotland, and increasingly widespread overnight across Ireland and into western Britain, a cold pool will overspread relatively warm SSTs, creating an environment with steep mid-level lapse rates and up to 500 J/kg CAPE. Numerous showers are likely as a result, some capable of producing copious amounts of hail, some gusty winds and sporadic lightning - more especially on Saturday night as instability increases. As such, a low-end SLGT (25-30% chance) has been introduced along some western coasts. 

image.thumb.png.e48d4b2f70fb90d8110167eed98f18ba.png

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7 hours ago, Mitch the motorbike storm said:

What time will the squall line reach ramsgate area?

Around 10pm looks likely. UKV going for a bit later, AROME a bit earlier. It's worth radar watching so you know exactly when it's coming.

 

12 hours ago, matt111 said:

Had one a few years ago here which had thunder, it also brought a few trees down nearby. 

I had thunder from the one during storm Ciara early this year, but the rain and wind at the time wasn't really squall-like. Squalls always seem to want to break apart over my area, hence I never believe the hype about them! Even the best squalls I've seen have not been as intense as I'd like, and they're always over in about 2 minutes unless you're lucky enough to have a front that's stalling a little.

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Squall line could strengthen as it arrives in SE England and E Anglia later, as one or two waves along the front run up from the SW and instability also increases with the waves from the SW. Broken line segments could evolve, which allowing deeper convection, could bring strong winds aloft to the surface, plus backing surface winds ahead of the waves could allow stronger updrafts to rotate to form a tornado, though consider it a low risk. My convective/storm forecast for today:

CONVECTIVE & THUNDERSTORM OUTLOOK - SAT 24 OCT 2020

stormmap_241020.thumb.png.6d0636527bc3e7b9e382238dcf81d994.png

Issued 2020-10-24 09:13:59
Valid: 24/10/2020 0900 - 25/10/2020 0600

Forecast Details

Long-wave upper trough axis to the west of the British Isles will slowly edge east towards NW Europe on Saturday, with a strong cyclonic SWly flow across the UK and Ireland. A deep area of low pressure will be slow-moving to the NW of Britain during the day, but will drive an active cold front SE across England and Wales.

With a strong SWly flow at all levels parallel to the cold front moving southeast, accompanied by a strong jet aloft, a leading edge squall line is expected to accompany the frontal passage across England and Wales through the day, the front clearing E Anglia and Kent around midnight. There are hints from models that one or two waves may develop along the front, as subtle shortwaves run NE in the strong SWly flow aloft.

Instability will be generally too shallow along the squall line as it passes over much of England and Wales for more than strong gusty winds (40-50 mph locally) and a brief intense burst of rain. With risk of lightning expected to be low.

However, waves moving along the front into S and SE England coinciding with an increase in instability from the SW later this afternoon and early evening could allow some broken convective line segments to develop with deeper convection. This deeper convection may allow strong winds aloft to move down to the surface in stronger downdrafts, leading to a risk of isolated damaging wind gusts of 50-60mph, particularly towards SE England and around the coasts in these areas.

In addition, backing of surface winds ahead of one or two waves running along the leading surface cold front this evening across SE England could allow stronger updrafts in these broken convective line segments to rotate and perhaps produce an isolated brief tornado across southern counties of England late afternoon/early evening, as the front passes through. So have issued a severe risk areas for S and SE England / E Anglia.

Following the cold front, Polar maritime airmass will be unstable, particularly around coastal areas, as cold air aloft over seasonally warm SSTs creates instability over sea and onshore over windwards coastal areas. So heavy showers pushing ashore across W Scotland, western Ireland, NW England, Wales, SW and far S of England could be accompanied by hail and thunder overnight.

Issued by: Nick Finnis

 

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Too far north for anything of interest here bar watching for an outside chance of being enough rain to increase another month hitting the 100mm club.

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16 minutes ago, Mitch the motorbike storm said:

Sooo I shouldn't chase the squal on my motorbike? ....

Put some sails on it,it might go faster😀

just kidding

stay safe😉

 

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2 minutes ago, MP-R said:

Looks like the first squall line will be a bit of a dribble. Is there likely to be a more potent second one?

Not according to the UKV. The first one will pep up as it moves further East, though.

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3 hours ago, Mapantz said:

Not according to the UKV. The first one will pep up as it moves further East, though.

Signs of it beginning to do so now. 

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