27th Aug 2011 - Storm/convective Forecast Discussion And Reports

[Coast]

Well, I've got to say I wasn't expecting to see a thread open for today!

Storm Forecast

Valid: Sat 27 Aug 2011 06:00 to Sun 28 Aug 2011 06:00 UTC

Issued: Sat 27 Aug 2011 03:57

Forecaster: VAN DER VELDE / KOROSEC

A level 2 was issued for N Italy, Austria, Slovenia, across E Czech Republic and W Slovakia into central Poland mainly for large hail and severe wind gusts, and perhaps a tornado. Excessive convective rain chance exists along the south flank of the Alps.

A level 1 was issued for areas surrounding the level 2 mainly for some large hail and severe wind gusts and excessive convective rain.

A level 1 was issued for southern Scandinavia mainly for excessive convective rain, large hail, and some chance of tornadoes.

SYNOPSIS

A deep trough over western Europe now acting as a negative tilted trough with its axis crossing the central Europe during the day. At surface, a sharp cold front extends from southern Scandinavia towards the southern Alpine region. The front gets pushed eastwards and serves as a focus for robust convective activity over the highlighted areas. Cool maritime airmass overspreads western Europe and results in scattered convection.

Forecaster: Dan

Last Updated: 23:13 Friday, 26th August 2011

Valid: 00:00 Saturday, 27th August 2011 - 23:59 Saturday, 27th August 2011

Areas Affected:

MDT: C + SW Scotland, Borders, NE England

SLGT: C + S Scotland, Northern Ireland, N England, N + E Midlands, East Anglia

Synopsis:

An upper trough becomes an upper low as it slowly migrates northeastwards towards Norway, leaving the United Kingdom in a showery rPm NWerly airmass. Local convergence will provide the greatest focus for significant convection.

Discussion:

Cold upper levels will steepen lapse rates as diurnal heating occurs, leading to several hundred J/kg CAPE. This, combined with local convergence zones and topographical uplift will result in numerous showers across many parts of the country, and thunderstorms likely across southern Scotland, northern and eastern England given ELT's as low as -50C in places. Embedded troughs and areas of PVA are likely to enhance convection and thus thunderstorm coverage across the threat areas.

There is a lack of any noteworthy DLS or LLS, and thus the severe weather threat will be limited, although given the setup a CZ-type funnel is possible. Smail hail is likely in some showers given cold air aloft, possibly >1cm over East Anglia.

It must be noted that the greatest instability will slowly migrate northwards and eastwards during the day as the upper low continues it's journey northeastwards, and thus those areas in the southern portions of the SLGT area have their best potential until mid-afternoon.

Ruddy Belgium again!!!!

Met O Chart has it over the East of the country, but not as far South as ESTOFEX:

CAPE is patchy and gone by 15.00 Hrs:

A little patch of something around Hull?

Higher level not too bad either:

So an Eastern England possibility, maybe around the Humber later on in the morning/early afternoon?

[vortex_liam]

I'm probably out then today..

[NO LONGER POSTING]

Erm...Just had a very sharp shower...And a very high tower moving through..Black sky! And a faint rumble..

[Aaron]

Yeah, probably no chance for me either. I think East Yorkshire/Lincolnshire have had enough storms this year, send some over here. :

Edited August 27, 2011 by aaron

[Nick F]

Convective / Storm forecast - Issued 27/08/2011 10:30

Forecast Summary Map

Click for full size

Valid: 27/08/2011 10:30 - 28/08/2011 06:00

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

Synopsis

Deep negatively-tilted upper trough extends SE across the UK down towards Nern Italy during the forecast period. At the surface, at 18z Sat a ridge of high pressure over the east N Atlantic extends S from Iceland down to the W of Iberia, deep area of low pressure centred just NE of Scotland pulling a cool maritime W to NWerly flow across the UK - unstable in the N and E

… SCOTLAND, N and E ENGLAND, N EIRE …

Cool W to NW flow characterised by steep low to mid-level lapse rates towards Nern and Ern UK towards upper trough will allow numerous showers to develop widely across UK. Greatest CAPE is likely to be across Scotland, N and E England beneath the coldest air of the upper trough over N and E UK, scattered thunderstoms are likely to develop here ... vertical shear will be rather weak where greatest instability is likely and temperatures/dew points fairly low - so no severe weather is anticipated ... though showers/storms maybe accompanied by hail, gusty winds and torrential rain leading to localised flooding. Any storms should fade after dark.

[Methuselah]

Some quite rapid convection going on, here....

[NO LONGER POSTING]

Some quite rapid convection going on, here....

Agreed..But why here? I'm not in the risk zone today..

[Nick F]

Some quite rapid convection going on, here....

Aye, clouds are beginning to tower now after a fairly clear start to the morning. Wouldn't rule out some heavy showers with the odd crack of thunder for London later, though think most action will be to north across E England and S Scotland.

[NO LONGER POSTING]

Aye, clouds are beginning to tower now after a fairly clear start to the morning. Wouldn't rule out some heavy showers with the odd crack of thunder for London later, though think most action will be to north across E England and S Scotland.

Ddi you hear that thunder about an hour ago?? Very faint for me..

[Nick F]

Ddi you hear that thunder about an hour ago?? Very faint for me..

No, a few sharp showers across far SW of London recently, though.

[Guest]

Eek, sounds like one of those days when we're the breeding ground here then, and E Mids, Lincs and E Yorks gets the main action.

A cluster of heavy showers working their way from NW England towards West and South Yorkshire. We NEED these to turn thundery over the next few hours, otherwise it's game over for another day!

[Aaron]

Wow-za, massive, towering clouds to my east AND west. Convection starting here.. and agreed Steve, we need some action!

Edited August 27, 2011 by aaron

[NO LONGER POSTING]

really getting going now!!!!! WOWOWOWO

[Chris K]

I'm not expecting anything here today, had 4 flashes of lightning yesterday that's it for 2011 haha. A few moderate showers forecast here, but some big dark clouds are forming just to the North of here as they head off to the SE.

[vortex_liam]

that shower is heading to me its getting dark...

[matt_in_dudley]

Currently a light shower here at present, nothing fun! Better not rain when i decide to go into Walsall later

[Supacell]

I wonder if the Bradford storm shield can be broken today? I may be too far west though.

[Aaron]

I wonder if the Bradford storm shield can be broken today? I may be too far west though.

I'm wondering too. West & South Yorkshire = no go for storms this year!

[Coast]

Blimey just got the car washed and the roof down and a huge black cell has moved in, out of a clear blue, from the North West with some menacing rain approaching. No thunder or lightning, but it is going to pelt down! I think my roof switch is connected to a rain magnet....

[Supacell]

I'm wondering too. West & South Yorkshire = no go for storms this year!

South Yorks hasn't done too badly as far as I know. But Bradford and Leeds have had a raw deal. There has been one storm over Bradford this year and I wasn't here to see it.

There are showers to the west but they aren't thundery yet.....

[Aaron]

A shower here now.. nothing great though. Still time though.

[Aaron]

A heavy shower has developed right to my east, we got the light bit.. story of 2011

[Eskimo]

Someone has split pepper all over the UK

[loopydreamer]

woah THUNDER in chatham!!!! YAY!!!!

[Costa Del Fal]

Some really good convection around here so far and 2 downpours already. No thundery activity expected here but after last night, Im fine for now. :lol: