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

[gottolovethisweather]

Without looking at the Skew-t, my guess is that we have a warm moisture rich surface layer which is overridden by a warmer still drier layer. above this we are seeing an upper layer of air that is forecast to destabilise both as the day progresses and as the further north and west one goes.

This has led to the upper based line of storms seen earlier in a line from Chichester towards London. Anything further east and south of this is held together by more stabilised upper air which is forecast to become more destabilised as the day progresses. I would think that anything west of the line already established could miss out later this afternoon.

Thanks for the update Chio. Part of me is not expecting anything as was suggested, however the humidity and associated insolation leads me to think that later, maybe............ oh well, I'm relying on you English Channel.

AT 27.4c, DP 20.3c, 65% humidity, sunny intervals with multi-layered patches of clouds with unknown names (not all everyday cumulus)

Edited August 19, 2012 by gottolovethisweather

[Suburban Streamer]

Without looking at the Skew-t

Someone has posted the skew-t link above

Edited August 19, 2012 by Suburban Streamer

[5thchang]

can only get the 00z

http://weather.uwyo.edu/cgi-bin/sounding?region=europe&TYPE=GIF%3ASKEWT&YEAR=2012&MONTH=08&FROM=1900&TO=1900&STNM=03882

[Biggin]

France seems to be currently producing the goods and sending it our way Although I do think it could be a tad farther East that will see the best of the action.

[Tilly]

Hey, are we due any storms in our little corner in Kent later? We're Trying to decide if our BBQ will be an indoor or outdoor affair. It's super cloudy here at the mo, sun trying to break through and spitting about.

[5thchang]

Here is the 12z skew

http://weather.uwyo.edu/cgi-bin/sounding?region=europe&TYPE=GIF%3ASKEWT&YEAR=2012&MONTH=08&FROM=1912&TO=1912&STNM=03882

[knocker]

can only get the 00z

http://weather.uwyo....1900&STNM=03882

The 12z is due out about now. It's done remotely from Camborne so is always slightly delayed since I retired.

[Supacell]

I'm now 5 miles south of Grantham and it is horribly hot, dread to think what it feels like in the SE. Hoping I have not wasted my time today if that line through London and then into East Anglia was the forecasted storms.

[NorthNorfolkWeather]

Tiny cell just popped up overhead with a rumble of thunder - there was nothing there 15 mins ago!!

Three nice flashes and some large drops of rain. Closest falsh under a mile away with deep rolling thunder. Pretty elevated in terms of cloudbase, the clouds probably start from 8,000 ftt up.

Gone quiet now with a possible follow on coming from the southwest, I'm just surprised at the speed the storm is moving at, on the Radar, it looks in excess of 50 mph

[knocker]

Another look at the midday Hurstmonceux ascent.

[TEITS]

I'm now 5 miles south of Grantham and it is horribly hot, dread to think what it feels like in the SE.

Actually the current hottest temps are between London towards the Wash. Anywhere SE of this line is slightly cooler due to the showers surpressing the temps.

As you are near me I have to be honest I have no idea what will happen later and although the radar doesn't look promising, experience tells me storms could develop very quickly.

[Nick F]

Witnessed some high-based storms rumble NE through London earlier just after midday, didn't actually see any lightning but could hear thunder rolling way up in the clouds. All that has cleared away NE and it's back to hazy sunny skies again with little convection now downwind.

Eyes on whether anything can develop across the Midlands, Nern Home Counties up towards Lincs and E Anglia this afternoon. GFS shows wind convergence may trigger something - but could be isolated:

N-W storm forecast, late today as had other commitments:

Valid: 19/08/2012 14:00 - 20/08/2012 06:00

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

Synopsis

Upper low to the west of the British Isles and upper ridge over central and southern Europe is pulling a hot and moist airmass north over western Europe including England and Wales. A waving cold front lying across SW England, Wales and N England at noon will move slowly east this afternoon/evening before weakening and exiting eastern England Monday morning.

... SW ENGLAND, SE WALES, MIDLANDS, N ENGLAND, LINCS, E ANGLIA and SE ENGLAND ...

High-based storms have already developed from mid-level instability on the NWern edge of high wet bulb potential temperature (WBPT/Theta-w) plume skirting SE England/E Anglia - with sferics from London NE across E Anglia early this afternoon. These storms will continue to drift NE through E Anglia in the next few hours and are unlikely to pose a severe threat.

Further W and NW from SW England up through the Midlands to Lincs and N England, a conditionally unstable warm/moist airmass is in place ahead of cold front across Wales and N England. Dew points of 17-18C are common in this zone and with surface heating GFS generates 400-1000 j/kg CAPE. Weak convergence zone is indicated to form in this zone which will slowly shift east this afternoon, this combined with forcing from a weak shortwave moving NE will likely aid the development of isolated storms from mid-afternoon. Any storms that develop in this area will benefit from 50-70 knts of deep layer shear thanks to a strong southerly jet, so storms should quickly organise into multicell line segements and given strong instability indicated - a few supercells are possible. Any storms in this zone may be capable of large hail (up to 6cm), damaging wind gusts, torrential rain with risk of flash flooding and a few tornadoes - given strong low-level shear and lowering LCLs from the west. Despite the scale of threat of severe weather, have issued a SLIGHT RISK based on uncertainties of coverage of storms - which maybe isolated.

[knocker]

At 12z it was 82F at Wattisham and Cranfield.

[Terminal Moraine]

I don't feel very confident that anything will develop in this area this afternoon.

We narrowly missed the area of rain which moved north across western districts this morning and there has been a thick veil of medium level cloud since about 0830 g.m.t, suppressing any convection.

Nothing more than a few spots of showery rain so far this afternoon and nothing on the radar to the south and south west.

[Supacell]

Over on ukww, there is talk of storms running from Derby through Sheffield and towards York.

Then there is talk of Oxford through Leicester to Lincolnshire.

It is actually becoming too hot to withstand lol!

EDIT: I am liking Nick F's forecast. A breeze has just developed here and clouds showing a bit more development. I need to keep an eye out on convergence zones setting up. If anyone else wants to then:

http://www.xcweather.co.uk/

Edited August 19, 2012 by Supacell

[Norfolk Sheep]

The mass of rain which suddenly appeared is now clearing off into the N Sea and the sun is making an appearance, bit of a breeze and not quite as humid.....better visit mother while there's a lull in proceedings!

Edited August 19, 2012 by Norfolk Sheep

[A.J]

Over on ukww, there is talk of storms running from Derby through Sheffield and towards York.

Then there is talk of Oxford through Leicester to Lincolnshire.

It is actually becoming too hot to withstand lol!

I actually heard whispers & rumours that storms would fire slightly further west, through Worcester, Birmingham & especially Stafford, with possible supercells firing north of Wolverhampton, towards Cannock & Penkridge (which is right on my front door step) !!!!.....

(Actually, I must admit, those rumours & whispers were the voices in my head...I just wanted to feel better momentarily!.... )

[Wet'n'Dry]

Don't bother washing your cars! A brief shower earlier has left my car covered in a fine dust. Temps here earlier were around 29c, now 24c and not so humid.

[Supacell]

(Actually, I must admit, those rumours & whispers were the voices in my head...I just wanted to feel better momentarily!.... )

I would get that seen to mate

I actually had a dream last night that I saw a tornado and ended up being chased by it and it then came over my car and the car was shaking with a huge roaring sound. Couldn't have been a premonition though as I had my 2 kids with me and unless they are hiding in the boot they are certainly not here.

Would love to see a tornado though, seen 2 funnels but never a tornado.

[Sprites]

2 rumbles of thunder here 1.20 , 17 thunder days now.

[osmposm]

Who has storms in London ????

Had a promising beginning here in Putney just before 1 pm: darker and darker from the SSW, frequent rumbles of thunder getting steadily louder and closer, a few spots of rain, then falling heavier and heavier, on the verge of a real deluge...but then petered out again after not many mins - I think most of it slid past a bit east of me on its way towards East Anglia.

The few minutes of heavy rain have left a scatter of classic pale brown (?)Sahara dust on the cars. But otherwise a disappointment.

Edited August 19, 2012 by osmposm

[SnowJoke]

Sky covered by a fast moving Ac layer here now, with some areas looking quite dark, looking through any gaps you can see towering cumulus heading upwards in narrow pillars, so still looking ok if convection can get a hold and build. Currently close to 29'c here in the middle of CMK even with the cloud cover.

[chionomaniac]

I am no expert on the Skew-t's but it looks like those posted earlier (thanks) show the scenario earlier described and for those in the SE. The threat looks like it is diminishing as the risk moves east from the 12Z reading for the far SE whilst a further risk zone remains in place further NW as Nick F highlights.

[bobbydog]

nice little storm here this morning, clouds looked spectacular. at one point, the mammatus clouds formed a pair of evil eyes looking down at me! but by the time i got my camera they had gone. never mind, more please!!

[Muffelchen]

All gone out to sea it seems but hopefully Nick F has it nailed. Not much for 'the slot' on the radar at the moment but it has gone cloudy up here and the temp has been holding steady for the last hour or so at 22.5°C with a humidity of 68%. Needs to get a bit hotter I feel and that will only happen if the cloud cover breaks up and lets the sun do its work.

Has the right 'feel' about it though but I am not convinced I will see anything today. Been a bit more miss than hit here over the last month or so and we usually do very well (not far from Lincs!).

Muff