Convective / Storm Risk Discussion - 21st June 2013 onwards

[Lynxus]

I have noticed a little bit of elevated convection over parts of Wilts & Oxon on my way home this afternoon, some very patchy Ac with virga...........I know, not exactly raging thunderstorms, but I've used the word 'convection' so it is on topic

 

Raging convection.....

 

Teheheheh Gigigle.

 

/toomuchsunshine

[sunnijim]

Simuler here in SE London,at around 6pm after a still day we had some lively gusts of wind,its now dead calm and clear again.

[Dan the Man]

Plenty of CAPE to play with.

[Jax]

Plenty of CAPE to play with.

no good without all the other ingredients though.

[dave48]

Met Office forecasting a few thundery showers across east midlands/east anglia/south east tomorrow.

 

NMM has CAPE values up to 1000 j/kg with temps of 29 and dewpoints of 16+

[nitro_deluxe]

Risk minimal but yes certainly there - quite a spell this one, heat has overcome the need for sparks..for time being anyway.

Potential must surely be going up now though

[ZONE 51]

Met Office forecasting a few thundery showers across east midlands/east anglia/south east tomorrow.

 

NMM has CAPE values up to 1000 j/kg with temps of 29 and dewpoints of 16+

That be amazing been keeping check on here and Met O..

Would cool air a little I think if we get heavy downpours, the grass is yellow around here everywhere it needs those storrms well the rain part of them any way!

[Coast]

Some faint hope for tomorrow...

 

http://ukasf.co.uk/storm-forecasts/254

 

MO have also switched from sun to 40% precip risk in the afternoon for my area.

 

Expanding that link:

 

 

Synopsis:

 

At the surface a large anticyclone continues to dominate across the British Isles, but with heights aloft falling slightly as a heat low develops over SE England.

 

Discussion:

 

... E ANGLIA, SE + CS ENGLAND ...

 

Strong diurnal heating will yield some 1500+ J/kg SBCAPE, although largely capped in a very warm but relatively dry airmass. There is the potential for isolated thunderstorm development across parts of the Home Counties from mid-afternoon through to mid-evening, as a strengthening seabreeze develops a notable convergence zone, coupled with the development of a thermal low. Such forcing may be enough to break through the 'cap' locally, particularly where slight upslope flow over the Downs/Chilterns is present. Hence the probability of thunderstorm development (only 5-10% chance) is considered less than on Saturday, and it is likely that the majority of the SLGT area will remain dry.

 

Shear is very weak, so any storm that does manage to develop will be poorly-organised and fairly short-lived, but with the potential for some small hail. PWAT values near 30mm and very slow storm-motion (in a general NW-SE direction) could result in very local high rainfall totals. Any storms will decay through the evening as diurnal heating subsides.

 

 

Nothing from ESTOFEX and SkyWarn and TORRO seem to have given up!

[Coast]

Well here's you CAPE for fuel:

 

 

 

 

Convergence seems to be to the SW of London, but that could move anywhere within a 40 mile radius of London and the coast

 

 

Here's an area of convective precip that GFS likes:

 

 

Lapse rates are silly!

 

 

Delta Theta-e chart highlights the main area of a possible isolated thunderstorm for me and maybe a very low risk of a microburst? 

 

[Coast]

If you want to see isolated, NMM has tiny pockets of potential all across London and all counties surrounding it later!

 

 

 

 

 

Very hit and miss.

 

 

 

 

 

 

[Coast]

Forecast Skew T for London would suggest the cap is too strong:

 

 

Lets get this convergence going then 

[VillagePlank]

London Heathrow, 15z,

 

 

Small convective potential today despite very strong insolation means showers are unlikely. Looks to me as if that CAPE is going to go to waste again. Should they occur, then I would expect that showers will readily develop to thunderstorms with frequent lightning, potential for hail etc etc. It's unlikely they will form although some around just north of London can't be ruled out.

 

Shame.

Edited July 17, 2013 by Sparkicle

[Nick F]

Loving the 00z ECMWF this morning, which suggests a thundery breakdown from the south next week as an upper low moves in to the SW early next week and thundery low pressure develops over Biscay and W France:

 

 

Unfortunately GFS is not having any of it and keeps us dry and settled, and with the way things have panned-out storm-wise (or lack of) this summer so far, not holding my breath!

 

Anyway, risk of an isolated storm popping up from the heat of the day over the Chilterns and Downs of Berkshire and Wiltshire later this afternoon/evening.

 

Then risk of isolated storms for eastern Scotland, Wales and SW England tomorrow.

Edited July 17, 2013 by Nick F

[Summer Sun]

Synopsis:

 

At the surface a large anticyclone continues to dominate across the British Isles, but with heights aloft falling slightly as a heat low develops over SE England.

 

Discussion:

 

... E ANGLIA, SE + CS ENGLAND ...

Strong diurnal heating will yield some 1500+ J/kg SBCAPE, although largely capped in a very warm but relatively dry airmass. There is the potential for isolated thunderstorm development across parts of the Home Counties from mid-afternoon through to mid-evening, as a strengthening seabreeze develops a notable convergence zone, coupled with the development of a thermal low. Such forcing may be enough to break through the 'cap' locally, particularly where slight upslope flow over the Downs/Chilterns is present. Hence the probability of thunderstorm development (only 5-10% chance) is considered less than on Saturday, and it is likely that the majority of the SLGT area will remain dry.

Shear is very weak, so any storm that does manage to develop will be poorly-organised and fairly short-lived, but with the potential for some small hail. PWAT values near 30mm and very slow storm-motion (in a general NW-SE direction) could result in very local high rainfall totals. Any storms will decay through the evening as diurnal heating subsides.

 

Valid: 2013-07-17 00:00:00 - 2013-07-17 23:59:00

 

http://ukasf.co.uk/storm-forecasts/254

 

Edited July 17, 2013 by Summer Sun

[Coast]

 

http://ukasf.co.uk/storm-forecasts/254

 

 

Think I did that one!! :lol: 

[A.J]

Loving the 00z ECMWF this morning, which suggests a thundery breakdown from the south next week as an upper low moves in to the SW early next week and thundery low pressure develops over Biscay and W France:

 

EC_0000_138.pngEC_0000_144.png

 

Unfortunately GFS is not having any of it and keeps us dry and settled, and with the way things have panned-out storm-wise (or lack of) this summer so far, not holding my breath!

 

Anyway, risk of an isolated storm popping up from the heat of the day over the Chilterns and Downs of Beyesrkshire and Wiltshire later this afternoon/evening.

 

Then risk of isolated storms for eastern Scotland, Wales and SW England tomorrow.

yes, Fergie on points west forecast last night suggested the hint of a rogue storm for the east of our region over the Marlborough downs which suits fine as that's pretty much where I am!

 

just to add in anything does show signs of developing over the downs, I'll take a quick trip up to Barbury Castle near Chilseldon armed with camcorder as it'll be a perfect viewing spot

Edited July 17, 2013 by ajpoolshark

[storm1080]

Latest 6z GFS...I'm up Portsdown Hill Mon evening and a burger from Mick's van, getting my deckchair out and selling tickets for admission lol - Kerboom (that's a technical term)

Edited July 17, 2013 by storm1080

[East_England_Stormchaser91]

Latest 6z GFS...I'm up Portsdown Hill Mon evening and a burger from Mick's van, getting my deckchair out and selling tickets for admission lol - Kerboom (that's a technical term)

If that comes off, the whole UK is going to be like a giant sonic boom disco event with strobe lighting!! 

Getting a bit carried away there, but good god, it will probably match up to those plumes of the 80s and 90's easily.

Edited July 17, 2013 by East_England_Stormchaser91

[Coast]

I'm up Portsdown Hill Mon evening and a burger from Mick's van, getting my deckchair out and selling tickets for admission 

 

Is that for all the cars there flashing their interior lights then?............

Edited July 17, 2013 by Coast

[paul m]

Latest 6z GFS...I'm up Portsdown Hill Mon evening and a burger from Mick's van, getting my deckchair out and selling tickets for admission lol - Kerboom (that's a technical term)

Hope us lot here get discounted tickets and if it does not happen a full refund

[Bogman]

Oh, I see you get a deckchair, burger and you have to pay to watch doggin' these days.

[storm1080]

Makes you wonder where it will really kick off after this weather, recall those amazing storms over Germany/Denmark last month - 

Is that for all the cars there flashing their interior lights then?............

and that as well, kill two birds with one stone

[Coast]

GFS overview has rain on the Hants/Dorest border this afternoon, but no thunderstorm:

 

[Azores Hi]

I'm at fleet services on the m3, just watching a line of small cumulus forming overhead, some taller towers/ congested mixed in. Convergence?

[Coast]

I'm at fleet services on the m3, just watching a line of small cumulus forming overhead, some taller towers/ congested mixed in. Convergence?

 

Could be AH, it was in some of the models and forecasts earlier

 

Edited July 17, 2013 by Coast