Uk Convective General Discussion & Forecasts, 16th August 2012>

[Coast]

Please discuss potential and actual weather for Thursday 16th August onwards. We have a thread open specifically for the stormy and convective weather due during 15th August here:

http://forum.netweather.tv/topic/74133-stormy-wednesday-15th-august-2012/

[AWD]

Mmmmmmmmmmm, interesting....................................

[Harry]

Lol that was what I was coming on here with....some storm porn to get us through todays inevitable let down

[Dan the Man]

Have you given up on today already?

[Supacell]

Well after todays let down for 95% of the storm wanting population what can we look forward to this weekend.

GFS is showing some very high temperatures and extreme values of CAPE. The concern is that it is all in the SE and EA, so the usual eastward shift could well push this over to the near continent. I am also concerned that a strong cap could stop anything forming at all for the areas with the highest CAPE, although it does look like it could destabilise on Sunday ahead of a slow moving cold front across the central slice of the country....

... and it is that cold front that could provide the greatest chances of storms for wherever it is situated. Overall there is an exciting weekend coming up with some explosive storms a possibility if everything turns out right.

[AWD]

Well after todays let down for 95% of the storm wanting population what can we look forward to this weekend.

GFS is showing some very high temperatures and extreme values of CAPE. The concern is that it is all in the SE and EA, so the usual eastward shift could well push this over to the near continent. I am also concerned that a strong cap could stop anything forming at all for the areas with the highest CAPE, although it does look like it could destabilise on Sunday ahead of a slow moving cold front across the central slice of the country....

... and it is that cold front that could provide the greatest chances of storms for wherever it is situated. Overall there is an exciting weekend coming up with some explosive storms a possibility if everything turns out right.

I agree with your last paragraph. Whilst the South East has epic amounts of Cape, there is little in the way of a trigger here.

However, on Sunday especially, there is respectful amounts of Cape across most of England & Wales. Wherever the front out west is situated on Sunday, it is on its Eastern flank, where it "collides" with the unstable air, that I think storms could be triggered.

At this timescale, it's one to watch, with no doubt twists and turns.

Also, pressure isn't that high this weekend, typically 1016mb, so is it not possible for homegrowns to develop on Saturday too?

[Cloud 10]

[Stuart]

Synopsis:

Upper low pivots northwestwards, with strong jets on both northern and southern flank, in particular across southern Britain, migrating north later. Ahead of the next frontal wave a day of scattered convection is anticipated.

Discussion:

Behind the occlusion diurnal heating will result in 500-700J/kg CAPE, allowing scattered showers and a few thunderstorms to form, primarily across northern and western Britain.

Across Scotland, a lack of shear will result in fairly disorganised 'pulse-type' convection, although this may become better organised for a time late afternoon and evening as shear begins to develop here in the wake of the upper jet.

Elsewhere, for Northern Ireland and northern England, up to 30kts DLS and 20kts LLS will allow convection to be better organised and longer lasting, with perhaps the most widespread coverage of sferics likely across central and northern portions of Northern Ireland.

Some stronger cells may produce some small hail. Slight backing of surface winds may allow a funnel or weak tornado to develop, more especially over Northern Ireland with slightly more favourable conditions

http://www.ukasf.co.uk/storm-forecasts/207

[Dan the Man]

2,000+ CAPE predicted according to Netweather on Sunday. That won't happen.

[Nick F]

Valid: 16/08/2012 00:00 - 17/08/2012 00:00

Headline: ... THERE IS A RISK OF THUNDERSTORMS FORECAST...

Synopsis

Upper and collocated surface low near W Ireland Weds night will drift back west across the Atlantic, allowing a ridge to build to the east on the near continent and the surface flow to back more southerly again. The southerly flow will be unstable in the west near a shortwave trough moving north over next 24hrs.

... SW ENGLAND, WALES, REP OF IRELAND, NW ENGLAND, N IRELAND and SCOTLAND ...

Short wave upper trough/cold pool will move north up the western side of the UK Thurs morning - steepening lapse rates in moist southerly flow. Stronger convection is therefore likely near the trough - with a few thunderstorms developing - initially the risk across SW England and Wales, then NW England and parts of Ireland in the morning hours with the risk subsiding from the south as the trough continues north. With greatest instability and risk of storms transferring north across N Ireland and Scotland in the afternoon. Although vertical shear will be rather modest (20-30knts at best), strong mid to upper winds will allow any convection to organise into line segments that may train over some spots to bring a risk of flooding. Also, storms may be accompanied by hail and strong wind gusts. Strong low-level instability, low LCLs, along with increasing low-level shear indicated across N Ireland in the afternoon suggests a weak tornado can't be ruled out with stronger updrafts.

Can also be found here: http://www.netweathe...onvective;sess=

[CreweCold]

Ok.....Crewe finally got a thunderstorm today......BUT I wasn't here to enjoy it as I was in Manchester. Apparently there was a lot of flooding as some kind of squall line moved through!

[richep]

Quite a heavy shower here right now

[Carl46Wrexham]

Well after todays let down for 95% of the storm wanting population what can we look forward to this weekend.

GFS is showing some very high temperatures and extreme values of CAPE. The concern is that it is all in the SE and EA, so the usual eastward shift could well push this over to the near continent. I am also concerned that a strong cap could stop anything forming at all for the areas with the highest CAPE, although it does look like it could destabilise on Sunday ahead of a slow moving cold front across the central slice of the country....

... and it is that cold front that could provide the greatest chances of storms for wherever it is situated. Overall there is an exciting weekend coming up with some explosive storms a possibility if everything turns out right.

Was a bit naff wasn't it? Didn't even turn out all that windy in the end if truth be told.

[Robbie Garrett]

GFS 18z seems to have upgraded this weekend a bit.

[Convective]

Looks good at the moment Robbie, hopefully it won't go down the pan once again..

Anyway, I am in the storm risk area for tomorrow so who knows? I am however thinking that the good CAPE and LI figures move through at about 10am, maybe a tad too early for a storm? :/

[Allseasons-si]

I have a storm risk of 72% on saturday and 65% on sunday,i can only dream lol,still a few days away so some chopping about in the coming days,i bet it will get shunted further east as per usual,that straggling front will be the do or die news on here for the next couple of days,here hopes that something will go this weekend

[paul m]

I have a storm risk of 72% on saturday and 65% on sunday,i can only dream lol,still a few days away so some chopping about in the coming days,i bet it will get shunted further east as per usual,that straggling front will be the do or die news on here for the next couple of days,here hopes that something will go this weekend

Those buggers in Lincs take all our big storms lol

[Allseasons-si]

Those buggers in Lincs take all our big storms lol

yeah,i nearly went there today if it wasn't the fact that everything was moving tooooooooo quickly and be a waste of jourmey.

[Michelle Baker]

Skies are looking a bit stormy this morning and ATD is showing a sferic near to Bristol

[SteveB]

Skies are looking a bit stormy this morning and ATD is showing a sferic near to Bristol

Theres a nice little storm to the south east, but it looks like it will miss our area

[NL]

ESTOFEX going for marginal storm activity today for the British Isles. But do state that storms that may initiate have the capability to become supercells given strong low level vertical wind shear and favourable veering profiles, tornadoes are possible if a storm can develop.

http://www.estofex.org/

[Supacell]

GFS 00z has made the expected eastward shift and pushes the ridiculous CAPE values back over the other side of the channel. It is only one run but I had concerns yesterday that this would be the eventual outcome. Having said this, i do not think the high CAPE would have been realised anyhow with a strong ridge sitting on top of the SE, preventing any storms from firing.

Still the chance of some storms developing along a SW to NE line from Bristol Channel through the Midlands into Lincolnshire on Saturday, slipping a little further south on Sunday. Yesterday, this line was forecast to be further north and would have affected my area. Still, if storms are still showing along this line by Saturday morning then I shall just have to take myself to them if they won't come to me

[Coast]

GFS 18z seems to have upgraded this weekend a bit.

But they also show:

What have we got to do around here to get a half decent storm? - crazy topsy turvy World we live in........

[Supacell]

But they also show:

Thats strange as the same model (GFS) also shows a 50-60% risk of storms SW to NE through the country on Saturday on the NW storm risk charts. Although agreement on the SE not seeing much.

[Coast]

I'm just not sure as the lightning wizard specific convection charts light things up from Wales into the Midlands, London and the Home Counties: