UK Convective General Discussion & Forecasts

[knocker]

These boys always seem to do a good job, and it seems that the cold front (as it strengthens) will turn into a squall line:

http://www.ukweather...r-Warnings.aspx

They should update their bookmark though.

[IanR]

Reports of a tornado in Manchester area on local radio, demolishing chimney stacks and ripping slates off

[BornFromTheVoid]

A very nice squall line moving in across Western Ireland at the moment. A lot of lightening reported on it's southern end

[Stuart]

Affected: SLGT: N Isles, NW Scotland, S + W Ireland, SW Wales, SW England

Synopsis:

Upper trough becomes a cut-off low over N Isles early in the period, followed by a significant upper trough moving slowly eastwards from the Atlantic later. Two 'bouts' of significant convection exist.

Discussion:

Cold mid-levels (typically -35C at 500mb) atop relatively warm SSTs will steepen lapse rates during the first few hours of the forecast period as an upper trough migrates northeastwards over Northern Scotland and the Northern Isles, becoming a cut-off low. Underneath said trough, significant convection will develop with ELTs potentially as low as -40C, capable of producing lightning and small hail. An overlap of >30kts LLS and >40kts DLS may promote the chance of some organised convection and perhaps a tornado/waterspout. Convective gusts >60kts are possible locally.

As the upper trough/low moves gradually away towards the Norwegian Sea from daybreak onwards, attention then turn to the approaching sharp upper trough to the W of Ireland. During the midday and afternoon hours, as cold mid-levels overspread the area and steepen lapse rates, noteworthy convection will allow sharp showers with local thunder and lightning to develop, with ELTs down to -30C. It is worth noting, activity may be late starting. Such showers are then forecast to move eastwards across southern Ireland towards western Wales and SW England during the late afternoon and evening hours, and hence the reason for the SLGT risk here.

http://ukasf.co.uk/storm-forecasts/143

[BornFromTheVoid]

Just got some thunder and lightning with that squall and it's still going strong

[Coast]

Did anyone here see this reported event?

Tornado in Anglesey

Published: 01 Dec 201

A TORNADO howls in from the sea on its way to ripping through terrified holidaymakers' homes — in ANGLESEY.

Its 78mph winds lifted caravans, destroying six, as families cowered inside at Sandy Beach Holiday Park on Monday. The North Wales park's owner John Seymour-Jones said: "It was so sudden. Caravans were lifted up and bits flew all over."

http://www.thesun.co...0-Anglesey.html

[essex coast matt]

Just had a small hail shower here, and i am sure i saw flash of lighting to my east out of window??

[Jane Louise]

SKYWARN UK SEVERE THUNDERSTORM WATCH #065

ISSUED: 1230UTC TUESDAY 6TH DECEMBER 2011 (GJ)

SKYWARN UK HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR THE FOLLOWING REGIONS:

NORTHERN IRELAND

WESTERN SCOTLAND

SOUTHWESTERN SCOTLAND

NORTHERN ENGLAND

NORTH WALES

MIDLANDS

EAST ANGLIA

IN EFFECT FROM 1500UTC TUESDAY 6TH TO 1200UTC WEDNESDAY 7TH DECEMBER 2011

LOW SYSTEM DEEPENING UNDER A STRONG JET CROSSING SE'WD OVER NORTHERN SCOTLAND

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...THUNDERSNOW...HAIL...LIGHTNING...STRONG GUSTS

DISCUSSION:

THERE IS GOOD SHORT-RANGE MODEL CONFIDENCE ON THE POSSIBILITY OF A SEVERE WEATHER EVENT DURING THE NEXT 24HRS. A DEVELOPING LOW SYSTEM NW OF SCOTLAND WILL DEEPEN AND ENHANCE WIND VEER AHEAD OF IT INTO WESTERN PARTS. UNDER A STRONG JET WITH TEMPS OF BELOW -30C AT 500MB ON IT'S NORTHERN SIDE, AN UNSTABLE AND HIGHLY SHEARED ENVIRONMENT WILL DEVELOP. ALTHOUGH STORMS WILL BE FAST MOVING WITHIN A STRONG OVERALL FLOW, DOWNWARD MIXING OF DRY AIR FROM BELOW THE JET MAY SERVE TO ENHANCE DOWNDRAFTING AND STRONG GUSTS. COPIOUS AMOUNTS OF HAIL MAY BE EXPECTED, ALTHOUGH NOT INDIVIDUALLY LARGE. THIS WATCH MAY BE UPDATED OR UPGRADED.

SPOTTER ACTIVATION IS REQUESTED AND SPOTTERS ARE REQUESTED TO REPORT ALL FACTORS EXCEEDING ACTIVATION CRITERIA.

http://www.skywarn.org.uk/current.html

[Sprites]

maybe a chance of squall-line type convection with the atlantic storm forecast for tomorrow .. , as the cold front crosses the U.K. in the evening.

[Weather Wizard]

This looks convective

this looks exciting red alert for the south

http://www.torro.org...te/forecast.php

[Jane Louise]

Heads up for tomorrow folks.

Storm Forecast from UKASF

00:00 Wednesday, 14th December 2011 - 23:59 Wednesday, 14th December 2011

Areas Affected:

SLGT: W + NW Scotland, N Isles, NW, W + S Ireland, W Northern Ireland, S + W Wales, SW Eng, SW Mids, CenS Eng, SE Eng

Synopsis:

Very cold mid-levels overspreads the forecast area, with widespread deep convection, particularly close to exposed western and southern coasts. Here the best potential for significant convection is expected.

Discussion:

Very cold mid-levels atop relatively warm SSTs will steepen lapse rates significantly, allowing several hundred J/kg CAPE to develop, with ELTs as low as -60C (exceptionally cold!). Consequently, widespread convective showers will affect many southern and western coasts exposed to W/S winds, with various lobes of vorticity and embedded troughs pushing showers inland along distinct bands, particularly downwind of Bristol Channel.

Convective gusts >55kts locally are possible, combined with >30kts LLS and >40kts DLS significantly increases the risk of tornadic development, particularly along south coasts (places notorious for scenarios like this include Bognor Regis/Selsey Bill for example). Given very cold air aloft, hail is likely in many of the showers, locally moderate in size, and in heavier downpours where the freezing level is brought to the surface, sleet and wet snow is also possible.

Upper trough moves across the country late on Wednesday, continuing the risk of showers, even inland, despite the lack of insolation.

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

[ZONE 51]

NetWeather Storm forecast has been issued.

Exciting all this potential for thunderstorms!

[Coast]

Yep, yet again we could be in the running today:

[Jane Louise]

Oooh look! I'm in the red circle again. Now, that's all I'm saying for now! :winky: best keep busy I suppose. :lol:

[Coast]

[Nick F]

Netweather have a storm forecast out for today, could get interesting later.

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

[Jane Louise]

:winky: :lol:

[Raidan]

Evening all,My sister and I have come across some sites reporting cb's in the bristol area,can anyone confirm this and if they are active,cheers

[Jane Louise]

Evening all,My sister and I have come across some sites reporting cb's in the bristol area,can anyone confirm this and if they are active,cheers

Just seen this Raidan, did anything come of it?

[Raidan]

Unfortunately Jane no it didn't,didn't even rain,I see this quite often on these sites but nothing ever conmes of it,only took a real interest because there was a chance of more activity here today,ah well I guess 2 days in a row was a lot to ask lol.

[ZONE 51]

MetO recent sat,

you can see the low center just off the West Wales coast, inland SouthEast England could see some squally showers move in, its been fairly quite so far but the latest sat here shows those white fluffy blobs moving towards Central South/SE and of course quite alot along the Coasts and Channel, thundery they could be, hail, squally gusts!

look at the NAE chart here where it shows the low center and ppn and compare on the sat above!

Edited December 15, 2011 by ElectricSnowStorm

[viking_smb]

had a storm last night about 1am ish

[Coast]

Had several flashes of lightning out to sea on the way home last night and then more at home. Around 20.30 the skies opened and there was a brief hailstorm. More flashes out in the Channel this morning

[Jane Louise]

There's a very big area of heavy rain near the Irish sea I think moving East! I wonder if it has any storms embedded in it. Fingers crossed for us storm enthuaists!

[Liam J]

Wow that is very intense Jane, real downpours embedded.

Good luck

Edited December 23, 2011 by Liam J