Uk General Convective Discussion & Forecasts, 10th October 2012>

[Robbie Garrett]

Just had the biggest rumble of thunder and lightning from Santa Clause just now in SE5!

Woke me up!! Twitter and radar confirms!

Merry Xmas!

[Coast]

A nice unexpected treat for Xmas for some today then?

Storm Forecast

Valid: Tue 25 Dec 2012 06:00 to Wed 26 Dec 2012 06:00 UTC

Issued: Tue 25 Dec 2012 08:22

Forecaster: GATZEN

A level 1 was issued for southern Spain mainly for severe wind gusts.

SYNOPSIS

A deep trough moves into Europe today, the cold front will extend from eastern Poland to the eastern Alps to the west Mediterranean Sea at the end of the period. Ahead of this cold front, an unseasonably warm and moist air mass has been advected into west and central Europe. A broad warm air advection regime is located downstream across eastern Europe.

DISCUSSION

The Channel region, Benelux countries

Western Europe is affected by a strongly-forced synoptic situation today. Latest water vapor satellite image indicates a dark region associated with the cyclonically-sheared flank of the mid-level jet stream. Strong QG forcing is expected and low-level winds have turned to south ahead of the cold front. A tongue of rich low-level moisture (6 g/kg) and neutral to slightly unstable lapse rates have lead to CAPE in the order of 200 J/kg as indicated by latest Brest sounding.

Latest radar images indicate groups of thunderstorms that have developed across the Channel region moving north-eastward. Although a line of thunderstorms did not evolve, storms may organize in the strongly sheared environment, and bowing segments are not ruled out. These may be capable of producing severe wind gusts given strong low-level winds and vertical wind shear (10-15 m/s in the lowest kilometer). However, the potential seems to be too low for a risk level. Main convective activity is expected to spread into the Benelux countries before the trough weakends across the North Sea and north-western Germany.

Across the British Isles, another trough will lead to QF forcing in a convectively mixed air mass from late Tuesday into early Wednesday. Showers and thunderstorms are expected. Given the strong vertical wind shear, isolated severe wind gusts are not ruled out. Tornadoes seem to be rather unlikely given the relatively weak low-level moisture.

[Buckster]

thunder ! - on Christmas Day morning - thats a first

Happy Christmas to all

(Essex)

[Supacell]

thunder ! - on Christmas Day morning - thats a first

Happy Christmas to all

(Essex)

Funnily enough was just talking at work the other day about the fact we had never heard thunder over the christmas period. Although, considering where I am that will likely be the case this year too.

Merry Christmas storm fans. Will soon be the season for it again

[Coast]

Looks like my part of the World may be a possibility in a couple of hours:

[Severe Blizzard]

Thunder at 3:37 am and 6:20 am at FLEET, HANTS.

Thunder at GUILDFORD reported at 6:22 am.

20.5 mm rainfall measured overnight at Fleet is the highest daily total so far this month.

[Coast]

ESTOFEX right on the ball this morning as I'm writing this in a thunderstorm!:

Storm Forecast

Valid: Thu 27 Dec 2012 06:00 to Fri 28 Dec 2012 06:00 UTC

Issued: Wed 26 Dec 2012 22:15

Forecaster: GATZEN

SYNOPSIS

Low geopotential is centred across Scandinavia. With the strong westerly jet, several vort-maxima travel from the Atlantic to eastern Europe. On Thursday, a ridge builds over the Atlantic, associated with an amplification of the European trough. Main focus of convective activity will be a short-wave trough moving south-eastward at the edge of the amplifying trough. It will affect the north Mediterranean region late in the period.

DISCUSSION

Southern British Isles and France

A tongue of moist Atlantic air will extend into northern France and the Channel region ahead of a cold front located to the west of the British Isles at Thursday, 06 UTC. A frontal wave will spread south-eastward during the day ahead of the approaching short-wave trough. Strong quasi-geostrophic forcing is expected ahead of the trough axis due to a strong cyclonically sheared flank of a mid-level jet maximum.

The strong forcing will affect a very moist air mass with almost neutral lapse rates especially in the northern portions where cold mid-level air is located. Models indicate some instability across the Channel region underneath the trough's base as well as south-east of the approaching cold front across France. Current thinking is that some storms will form indeed.

Strong low-level winds in excess of 20 m/s at 850 hPa and strong low-level vertical wind shear of 15 m/s (0-3 km) and 12 m/s (0-1 km) will be supportive for organized thunderstorms. Bowing lines may develop as well as mesocyclones. These storms will be capable of producing locally severe wind gusts. Additionally, soft hail will likely occur. A tornado is not ruled out given the strong low-level wind shear. A level 1 is not issued due to the marginal threat. Storms will weaken from the north later on due to the advection of colder low-level air.

Edited December 27, 2012 by Coast

[Coast]

Look at that area of convergence over us:

Amazing shear over France currently:

Not showing on the simple format GFS though:

[Ben Sainsbury]

Any risk of storms along Southern England today especially London?

[Coast]

Any risk of storms along Southern England today especially London?

Ermmm, you've not read the last couple of posts then??

[Nick F]

Potential for squall line development along an active cold front slowly clearing east across England and Wales tomorrow (Saturday) - shallow line convection may lead to strong convective gusts lowering to the surface given strong jet parallel to front - lightning wizard suggesting 60-65 knot gusts. Low risk of a tornado despite strong mid-level jet aloft and fairly strong low-level shear likely as winds veer with passage of front ... just doesn't seem to be enough LL instability to warrant a higher probability.

Another active cold front slowly clearing across southern parts on Monday (New Year's Eve), could bring a squall line too with risk of strong convective gusts and perhaps a greater chance of a tornado - with better looking curvature to the strong jet aloft of a strongly veering flow towards the surface - but dependent on how much low-level instability can develop - which will probably be enhanced towards Channel coast with the SST influence. Fax shows a wave develop on the cold front - which may enhance shear too.

Edited December 28, 2012 by Nick F

[Bobby]

Potential for squall line development along an active cold front slowly clearing east across England and Wales tomorrow (Saturday) - shallow line convection may lead to strong convective gusts lowering to the surface given strong jet parallel to front - lightning wizard suggesting 60-65 knot gusts. Low risk of a tornado despite strong mid-level jet aloft and fairly strong low-level shear likely as winds veer with passage of front ... just doesn't seem to be enough LL instability to warrant a higher probability.

Another active cold front slowly clearing across southern parts on Monday (New Year's Eve), could bring a squall line too with risk of strong convective gusts and perhaps a greater chance of a tornado - with better looking curvature to the strong jet aloft of a strongly veering flow towards the surface - but dependent on how much low-level instability can develop - which will probably be enhanced towards Channel coast with the SST influence. Fax shows a wave develop on the cold front - which may enhance shear too.

A lot of showers following on from the cold front tomorrow also, any chance of hail or thunder from them?

[Coast]

Storm Forecast

Valid: Sat 29 Dec 2012 06:00 to Sun 30 Dec 2012 06:00 UTC

Issued: Fri 28 Dec 2012 18:48

Forecaster: SCHLENCZEK

SYNOPSIS / DISCUSSION

A very intense low pressure system with a center pressure below 945 hPa around Iceland is the steering system for the weather in most parts of western and central Europe. Along the axis of the trough which will make progress from W Ireland towards Benelux. The greatest chance for some convection is in the vicinity of the trough axis. As most of the strong deep layer shear is found ahead of the convectively unstable region, severe convection should be rather unlikely. But as common for almost all strong extratropical cyclones, severe non-convective wind gusts will occur over western Europe, preferably in the warm sector over UK.

[Convective]

Nifty hail shower passed over recently

[Coast]

Thunder and lightning in Eastbourne!

[Ben Sainsbury]

Cell just passed North of here which woke me up to a huge boom of thunder with hail following on from it.

Edited December 30, 2012 by interestingweather

[MP-R]

Damn, didn't hear any thunder but my word was there a hailstorm at 7am this morning - very gusty winds and noise against my bedroom window (facing W).

[SteveB]

Damn, didn't hear any thunder but my word was there a hailstorm at 7am this morning - very gusty winds and noise against my bedroom window (facing W).

Yeah, was bashing against our bedroom window too which also faces north. Not the best direction to have your bedroom window facing as the wind and rain often batter the window waking me up.

[Coast]

Breezy old day out there, but is that all we are in for?

Storm Forecast

Valid: Mon 31 Dec 2012 06:00 to Tue 01 Jan 2013 06:00 UTC

Issued: Sun 30 Dec 2012 22:09

Forecaster: DAHL

A level 1 was issued across parts of the Atlantic Ocean off the Iberian coast mainly for severe wind gusts and hail.

SYNOPSIS

A wavy upper flow pattern persists on Monday, with a deepening longwave trough reaching western Europe late in the period. Ahead of this trough a plume of warm air is spreading across western and central Europe. A weakening upper low persists over the Aegean region.

DISCUSSION

... southern Ireland ... southern UK ... northern Iberian Peninsula ... French Atlantic coast ...

Showers and thunderstorms are anticipated to persist near the thermal trough axis over the Atlantic. Although the storm depth should become progressively more shallow as the system moves eastward, scattered lightning may still occur over the Bay of Biscay and adjacent coastal areas in the evening and overnight hours. It seems that there may be a small spatial overlap of decent shear (> 20 m/s DLS and > 10 m/s LLS) in the coastal regions of S Ireland/S UK and from NW Iberia to N France. This suggests that there may be a small risk of a few brief severe weather events, including a tornado or two. However, the threat is not robust enough to warrant a level 1 area.

More rain on its way for a time:

Plenty of shear and gusty wind in the SE:

[Chris W]

I have just driven over the M62 through a squall which occurred around 2-2:30pm, making for horrendous driving conditions.

That is not all, however, as within this squall I saw an intra-cloud lightning bolt and a possible second flash shortly after it. An unexpected bonus!

[Convective]

Lightning! Just had 2 flashes of lightning and deep thunder south of here! Looks beefy on radar!

[Sprites]

radio suffolk saying Beccles area had thunder and snow 12.30 today .

[Methuselah]

radio suffolk saying Beccles area had thunder and snow 12.30 today .

I never heard it...

[Marcus_surfer]

Just to mention there was a rumble of thunder here last night when the showers passed 14/1/13

[Convective]

Really good out there tonight. 25 strikes per hour in the middle of January aint half bad! Just been 2 strikes south of here, saw them faintly!