Convective/Storm Discussion Thread - 1st August onwards

[Supacell]

39 minutes ago, Dangerous55019 said:

Evening @NUT , do you not remember September last year? 

Absolutely, September can produce some corkers. September last year produced a number of them.

[NUT]

We didn't get September last year up here  Probably was a little pesimistic with my post earlier

Estofex maybe not looking too shabby...............

http://www.estofex.org/cgi-bin/polygon/showforecast.cgi?text=yes&fcstfile=2017082306_201708212132_1_stormforecast.xml

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Tue 22 Aug 2017 - 05:59 UTC Wed 23 Aug 2017

ISSUED 21:57 UTC Mon 21 Aug 2017

ISSUED BY: Dan

Plume of high WBPT will be drawn northwards across the British Isles on Tuesday, ahead of an approaching Atlantic upper trough. Shortwaves running ahead of the main trough will provide the focus for mostly mid-level instability release, resulting in elevated showers and perhaps a few thunderstorms - the greatest risk of deeper, more widespread convection seems most likely on Tuesday evening / night as better forcing arrives from the southwest, destabilising the plume.

Some uncertainty exists as to the extent of this destabilisation (especially considering the messy mix of stratiform vs convective precipitation), and hence how widespread lightning activity may be - a SLGT has been issued for now, though this could perhaps be upgraded locally to a MDT should confidence improve. In general, better forcing and shear will be found towards the NW, whilst instability will be more significant farther southeast. Should any convection become rooted in the boundary layer, more likely late afternoon/early evening, then there would be scope for an isolated tornado - particularly across northern parts of the Republic of Ireland into Northern Ireland. Some hail is also possible, but the greatest threat will probably be from localised surface water issues given embedded convective elements.

 

http://www.convectiveweather.co.uk/forecast.php?date=2017-08-22

[Flash bang flash bang etc]

Haven't kept up to date on things for a while as this summers been a bit awful since late July - not surprised to see there's nothing exciting in store for our parts despite a moment of excitement when I saw the lightning pic on the NW homepage

[Convective]

BBC forecasts are extremely reluctant to show high resolution graphics for between 1500 Tuesday and 0800 on Wednesday. No forecast all day has shown the rainfall forecast for this period. I think this demonstrates the complexity of the forecasting of the next 36 hours...

Edited August 22, 2017 by Convective

[Nick F]

Storm & Convective Forecast

Issued 2017-08-22 06:31:30
Valid: Tuesday 22 August 6am to Wednesday 23 August 6am

Day 1 Convective / Storm Forecast

Synopsis

Upper and collocated surface low (the weakened remnants of ex-Hurricane Gert) will pull a plume of warm and humid air of sub-tropical origin across the UK, which will destabilise across Ireland/N. Ireland initially then across Scotland and N England Tuesday evening/night.

… IRELAND, N. IRELAND, SCOTLAND, N ENGLAND and N WALES …

 A plume of warm and humid air advecting north across the British Isles on Tuesday, with wet-bulb potential (WBPT/Theta-w) values reaching 16-18C and characterised by steep lapse rates, will contribute to modest CAPE values reaching 300-700 j/kg ahead of cold front moving in across the far west during the evening and reaching N. Ireland, Wales and SW England early hours of Wednesday.

This potentially unstable airmass will be capped across much of the UK during Tuesday, however, falling heights and cooling aloft with approach of upper low from the Atlantic combined with divergence in left exit of jet stream, shortwave trough and drier air aloft moving NE across the west will create large scale ascent which will destabilise the plume across Ireland/N Ireland initially in the afternoon … supporting development of heavy showers and thunderstorms, which will then develop or spread northeast across N England then the southern half of Scotland Tuesday evening and overnight into Wednesday morning as forcing moves NE.

30-40 knots of deep layer shear, strong upper level winds/divergence and linear forcing along/ahead of surface cold front will support organisation of convection/storms into clusters/line segments capable of producing torrential rainfall leading to flash-flooding, strong straight-line winds and hail. Increasing low level shear ahead of cold front and low LCLs (Lifted Condensation Levels or cloud bases) indicated across the west may support an isolated brief tornado too across Ireland, N. Ireland and NW England during diurnal heating cycle before risk drops after dark as surface/boundary layer becomes stable and storms become elevated.

Have issued a MARGINAL risk, mainly for flooding, across Ireland, N Ireland, far N of Wales, N England and SW Scotland.

... SW / CENTRAL S ENGLAND ...

There is a risk of some elevated heavy showers and thunderstorms across the above areas, mainly this morning before perhaps waning, though risk of isolated thunderstorms along S coastal areas through the day and into the evening as warm moist advection destabilises in mid-levels.

Issued by: Nick Finnis

Edited August 22, 2017 by Nick F

[Nick F]

Some elevated thundery showers affecting Cornwall and soon Devon atm

[karyo]

1 hour ago, Nick F said:

Some elevated thundery showers affecting Cornwall and soon Devon atm

Up to yesterday, the euro 4 was not picking up this activity at all. 

[Dangerous55019]

Morning all 
Not much I can add to from my post last night, so to help back up what @Nick F, @Summer Sun, and @NUT have already posted about today, here are the very latest charts from the 06z run from the GFS. 
As always, good luck to everyone one with this, and lets hope that something goes bang later. 

[Rickoza]

This could be the one we've been waiting on up here for over 10 years!  Not had a decent storm in all that time.  Seems to be more interesting period 12-3am for just east of Glasgow, anyone confirm?

[Dangerous55019]

The current state of the sky around here at the moment... To be honest, I've seen better... But I've also seen much worse.

The sun is quite warm though... Fingers crossed for later. 

[karyo]

1 minute ago, Dangerous55019 said:

The current state of the sky around here at the moment... To be honest, I've seen better... But I've also seen much worse.

The sun is quite warm though... Fingers crossed for later. 

I am not that far from you, yet it is completely cloudy here and it has been all morning.

Hopefully you will be able to spot some development soon. I am stuck in the office till 4:30pm :-(

[East_England_Stormchaser91]

At last, a potential storm day! It's been a while! Let's hope it goes off with a decent bang to end August. I remember 22nd of August 2015 was an awesome day, and ranked as one of my best storm chase days. North Yorkshire saw a couple of belters that day along with the West Country.

I am however off to Belgium on Saturday, and I am already getting excitement building by what some of the models are going for over there! 

[Chris.R]

The sun is now out, 21.3°C. Foehn effect should assist with temperatures today in an approximate area with boundaries 52.8-53.6N,4.6-2.8W. 

[Windblade]

I know nothing has been forecasted but I'm still keeping a eye on the south east tonight and tomorrow. Sometimes stuff happens when you least expect it. Wishful thinking? Maybe, but with this short lived plume I think there's a slim/moderate chance we could get something. 

Edited August 22, 2017 by Windblade

[LightningLover]

4 minutes ago, Windblade said:

I know nothing has been forecasted but I'm still keeping a eye on the south east tonight and tomorrow. Sometimes stuff happens when you least expect it. Wishful thinking? Maybe, but with this short lived plume I think there's a slim/moderate chance we could get something. 

Well there are some elevated storms affecting devon... could be a good sign?? 

[wimblettben]

1 minute ago, LightningLover said:

Well there are some elevated storms affecting devon... could be a good sign?? 

Doesn't mean much for eastern areas though, unless something causes storms to break out away from coasts.

The stuff would have to shift a good few miles to be of any note for most of us further inland.

[Windblade]

Wind direction is coming from the southeast (france) and drawing up hot and humid air. I'm wondering if we may see any imports that develop in this hot air mass? Probably wishful thinking on my part (desperate for a storm after missing two this month over my house, and have yet to see any fork lightning this year at all).

Edited August 22, 2017 by Windblade

[Dangerous55019]

44 minutes ago, karyo said:

I am not that far from you, yet it is completely cloudy here and it has been all morning.

Hopefully you will be able to spot some development soon. I am stuck in the office till 4:30pm :-(

Morning @karyo 

The sky is changing rapidly around here... Lots and lots of fibreous convective clouds now appearing...  Hopefully... Fingers crossed. 

[Chris.R]

Warming up rapidly here, 22.5°C. The area I mentioned above is currently the warmest in the country with Rhyl, Hawarden and Valley at the top of the temperature table currently. Bodes well for later. 

[karyo]

23 minutes ago, Dangerous55019 said:

Morning @karyo 

The sky is changing rapidly around here... Lots and lots of fibreous convective clouds now appearing...  Hopefully... Fingers crossed. 

hi mate,

 

the sky is starting to clear here now with warm sunny spells developing.

[karyo]

The latest euro 4 is very poor for most of us! 

[NUT]

That lot in Ireland looking intense

[Windblade]

Ah well, if I don't get anything I shall nonetheless be entertained by everyone's storm pictures and tales! Keep them coming and good luck everyone. 

[Julian 777]

keeping an eye on northern coast of France at the moment