Uk Convective General Discussion & Forecasts, 12th to 14th August 2012

[Coast]

A new thread to discuss potential and actual convective weather

[twister2005]

Its getting closer :-)

Once this line of storms has passed will more develope behind it ???

[philglossop]

Sunny here now but hopefully those showers near the Lizard at present will grow and they're bang on track for Plymouth. Come on showers build, build!!

[Darren Bown]

Sunday last week saw the worst flash flooding prestwich had seen. I wonder if again sunday

Will be 'Storm Sunday' and I will actually see it as I'm off?

[IanR]

seems more optimistic that the thunder showers might affect north west england, but can they punch through the formidable wigan shield, i doubt it

[Supacell]

If i am heading from Derby at around 12-1pm then will i be in good time to catch stuff over the Midlands into NW England? I am hoping i will not be too late. The fact it is all so slow moving is a good thing though.

[Coast]

Nothing from ESTOFEX today so straight in with UKASF:

Storm Forecast Slight

Forecaster: Dan

Last Updated: 2012-08-11 22:14:00

Valid: 2012-08-12 00:00:00 - 2012-08-12 23:59:00

Synopsis:

A narrow plume of high ThetaE, associated with a shortwave trough, will continue to migrate northeastwards erratically across England, Wales and southern Scotland. Behind the plume axis, further convection is expected over Ireland.

Discussion:

... ENGLAND, WALES, SW SCOTLAND ...

As the ThetaE plume and shortwave continues to migrate northeastwards, destabilisation will occur locally allowing initially elevated storms to develop through the morning hours from the start of the forecast period. If sufficient insolation can be acheived, storms may become more surface-based by the afternoon.

Local effects will be key to ensure sufficient destabilisation for sferic acitivity, such as orographic uplift or local low-level convergence. Most models simulate up to ~800J/kg MLCAPE within the narrow plume, so this will be sufficient for fairly active sferic activity with each individual cell.

Up to 30kts DLS and 20kts LLS will result in well organised convection, including multicells, with the general emphasis shifting to NW Eng and SW Scotland during the afternoon.

With a backed surface flow, and sufficient helicity, there exists potential for a low-topped supercell over NW Eng/SW Scotland during the afternoon, primarily if storms can become surface-based. With also sufficient directional and speed shear, there is also the potential for a funnel or weak tornado. Such storms may also produce some small hail, and with >34mm PWAT coupled with slow storm motion, there may also be potential for some local flooding.

... IRELAND ...

Behind the main plume axis, diurnal heating will help generate a few hundred J/kg CAPE, with several showers and a few thunderstorms likely. Rather weak shear will mean showers/storms will be poorly organised, with rather sporadic sferic activity from 'pulse-type' storms. There may be some small hail from any stronger cells.

SkyWarn:

SKYWARN UK SEVERE THUNDERSTORM WATCH #047

ISSUED: 1900UTC SATURDAY 11TH AUGUST 2012 (GJ/SM/RB)

SKYWARN UK HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR THE FOLLOWING REGIONS: SOUTHWEST ENGLAND & CHANNEL ISLANDS WALES MIDLANDS NORTHWEST ENGLAND & ISLE OF MAN WESTERN SCOTLAND NORTHERN IRELAND

IN EFFECT FROM 1900UTC SATURDAY 11TH UNTIL 2300UTC SUNDAY 12TH AUGUST 2012

MATURE LOW SYSTEM TO THE SOUTHWEST, WITH A SLIM PLUME OF WARM MOIST AIR AHEAD OF A DEGRADING FRONT.

THERE IS A POSSIBILITY OF SEVERE WEATHER AFFECTING THE INDICATED REGIONS IN THE TIME PERIOD SPECIFIED. THREATS WITHIN THIS WATCH INCLUDE, BUT ARE NOT LIMITED TO:

HEAVY RAIN...STRONG GUSTS...HAIL...LIGHTNING...FUNNELS/WEAK TORNADOES

DISCUSSION:

THERE IS GOOD MODEL CONFIDENCE OF THE POSSIBILITY OF A SEVERE THUDNERSTORM RISK OVERNIGHT AND THROUGH TOMORROW. PRINCIPALLY OF CONCERN IS A NARROW PLUME OF HIGH THETA-E VALUES AHEAD OF A COLLAPSING COLD FRONT ZONE, BECOMING DESTABILISED AS A SHARP EXTENSION OF THE UPPER TROUGH PASSES OVER SOUTHWESTERN, WESTERN AND NORTHWESTERN PARTS OF THE UK THROUGH SUNDAY. OVERNIGHT TONIGHT, ELEVATED CONVECTION IS EXPECTED ALONG THE EDGE OF THE PLUME ACROSS SOUTHWEST ENGLAND AND MOST OF WALES. DURING SUNDAY, DAYTIME HEATING ALLOWS SURFACE-BASED INSTABILITY TO DEVELOP ALONG AND BEHIND THE FRONTAL CONVERGENCE WHICH MAY HAVE SUFFICIENT HELICITY TO SUPPORT ORGANISED STORMS EITHER IN A LINEAR FORMATION OR PERHAPS ISOLATED ACROSS THE MIDLANDS AND NORTHERN ENGLAND. AREAS BORDERING THE IRISH SEA MAY SEE STRONGER CONVECTION OWING TO COASTAL CONVERGENCE AND OROGRAPHIC LIFT, WITH INTENSE RAIN AND COPIOUS HAIL LIKELY. DRY AIR ALOFT SHOULD ALLOW FOR FREQUENT LIGHTNING ALSO. HOWEVER, WITH PRECIPITABLE WATER CONTENT AT ABOVE 3CM, THE PRIMARY RISK IS FOR BRIEF INTENSE RAINFALL, AND POSSIBLE SUCCESSIVE HEAVY SHOWERS AND STORMS ACROSS WALES AND SOUTHWESTERN PARTS DURING THE DAY. NORTHER IRELAND MAY ALSO SEE MATURING STORMS FROM EIRE, THOUGH EASTERN COASTS HAVE A HIGHER LIKELIHOOD OF STRONGER CONVECTION. THIS WATCH MAY BE UPDATED OR UPGRADED. PLEASE MONITOR WEATHER AND TRAVEL INFO AS NECESSARY.

21st OWS:

MLCAPE seems to be slap bang in the middle of the country by mid-afternoon:

SBCAPE is there too:

Low level lapse rates look good:

and maybe the threat of a short lived tornado or funnel in that area too:

Simple format GFS says:

Good luck!!!

[Supacell]

Staffordshire/Shropshire/Cheshire/Lancashire/Merseyside and East Wales this afternoon then

[DeepSnow]

There was a very nice display last night! After I turned my computer off because I thought it had gone from here it started off in the south west again, so although it was mainly distant thunder and lightning its the best I've seen since 2009, and even better because it was at night Good luck to everyone else today!

[Matty23]

Well it's hit Ludlow and nothing just plain old rain I theory I mite see my first storm in years but nope

[twister2005]

Anyone on here from gloucester way ? Any thunder from that shower ?

Edit just heard thunder :-)

[Jane Louise]

Anyone on here from gloucester way ? Any thunder from that shower ?

Edit just heard thunder :-)

Heard distant thunder but it seems to be movig to my NNW grrrrr

[twister2005]

Heard distant thunder but it seems to be movig to my NNW grrrrr

Noooo come this way storm !!!

[twister2005]

Although there is more building to the south :-)

[Nick F]

Posted in the old thread, but here's the Netweather storm forecast for today:

http://www.netweather.tv/index.cgi?action=convective;sess=

[Darren Bown]

All models seem to point to NE England

As a possible hot spot this afternoon!

Edit: NW not NE

[Coast]

Two areas of possible MCS to watch out for:

[Chris K]

That was an interesting morning of a slow moving thunderstorm. Its moved on now and it got fresher for about 10 minutes but now its gone really humid again. Bleurgh.

Anyway, nothing else forecast for here today, but I hear that this week could have some interesting, although potentially disruptive weather - especially Wednesday. Not sure if it will be convective in nature but we'll find out soon enough...

[AWD]

Interesting to note that Ian Fergusson has recently posted a forecast profile for Bristol at 1pm indicating further thunderstorm potential but diminishing later PM.

Wonder what else they are expecting then?

[Evening thunder]

Was attempting to film and photograph lightning last night, but it all seemed a bit out of focus.

I caught a couple pics, not that good as my camera was lying to me and telling me the pics were in focus at times when they weren't.. Still, looks ok as a smaller image/thumbnail lol:

Think I really need a proper camera like a DSLR even though my compact has some manual control of many things..

[Lynxus]

Shame this band didnt come to anything here.

Just had about 20 mins of rain and thats it.

Potential is around for the next 2 or three days but i cant see much happening.

[fromey]

its just horrible here now, still warm but low grey,misty cloud.

im hoping to see a bit of sun may to help build something else, but that might just be a pipe dream.

fromey

[joanna1971]

All diminished as it was heading for Shrewsbury yet again, just had a light splattering of annoying rain..grrrr .. Not as humid either now, when will I get a storm, can't see anything else exploding later

[Gord]

A few large drops of rain for here. Don't think it'll come together in this part of the world. Always that risk with things that are so slow moving...and to be fair, it was looking like a dud beforehand so shouldn't really be dissappointed. It can only get better when you start with expecting nothing.

But it's not over until it's over...just unlikely right now.

[Cloud 10]

North-West England looks to have the best chance this afternoon with some decent energy

available to fire the trough up a bit.

As some have already mentioned,Wednesday is looking "interesting"