Convective Weather UK

[Marcus_surfer]

At the moment, looking fairly good for parts of SW England and Wales. It looks good also for much of the Midlands with -4 LI by Wednesday's evening hours.

Increasing chance of heavy showers and thunderstorms

Good chance for Midlands seeing some cells, then these pushing eastwards in N England

Temperatures in the range of 17-18C but very breezy so it will feel much cooler than recent days

Edited July 12, 2010 by Marcus_surfer

[Coast]

ESTOFEX highlighting an area of NE England in their watch zone today:

Storm Forecast

Valid: Tue 13 Jul 2010 06:00 to Wed 14 Jul 2010 06:00 UTC

Issued: Tue 13 Jul 2010 05:51

Forecaster: KOROSEC

SYNOPSIS

An intense trough which resulted in widespread severe storms on Monday continues tracking NE-wards across Scandinavia, while another deep trough/upper low enters western Europe and will result in another outbreak sequence on Wednesday afternoon. A weakening mid-level low over Ukraine moves slightly towards SE while slowly building omega-like ridge pushes into central Europe again.

At surface, a strong frontal system associated with the afforementioned robust trough serves as a focus for an outbreak of severe storms across Sweden. The cold front extend southwards into western Poland by the afternoon, while strong WAA ahead of the trough pushes warm front into the northern Scandinavia.

and tomorrow??????

[Nick F]

Looking at the 12z GFS parameters for storms tomorrow, my attention is initially drawn to E/NE England from Nern Cambs around the The Wash up through Lincs into S Yorks and N Yorks for best potential of some strong storms developing with potential for damaging gusty winds, large hail and perhaps one or two tornadoes towards early evening. Why? Well, GFS models best potential instability in this area (several 100 j/kg CAPE); overlaid by strong speed shear with proximity of the strong jet running up the east coast - which will allow cell organisation; some drier mid-level air moving in from the south increasing instability; and also increasing low-level shear as surface winds back SE'erly against the mean SSW/SW flow further aloft. Deep layer shear maybe sufficient combined with increasing low-level shear for rotating updrafts in any strong storms which may perhaps bring an enhanced risk of a tornado, though strong wind gusts and hail seem the most likely severe threat with any storms.

Bulk wind shear generally weakens considerably away from eastern England the further west you go, so general non-severe storms will be more likely with non-severe gusty winds, hail and torrential rain accompanying stronger cells.

Far Nern France and the Low Countries looks at a greater risk of supercells with all the severe parameters coming together tomorrow afternoon/evening of stronger instability enhanced by mid-level dry air intrusion, strong upper winds and strong DL shear and LL shear, so would expect to see some nasty supercellular storms moving north over that region tomorrow PM, perhaps the edge of the storm system clipping the far southeast corner, though unlikely with the severity as on the continent.

[Nick F]

Yes, quite a good forecast skew-t for strong storm development there Weather09, dry air intrusion at 600mb, plenty of instability, winds backing towards the surface, fairly good hodograph top right hand corner. North Cambs up to Humber I would think would see good potential of a strong storm developing tomorrow afternoon.

[Stuart]

Good Morning

And for Today

Storm Forecast Issued: 2010-07-13 22:07:00

Valid: 2010-07-14 00:00:00 - 2010-07-14 23:59:00

Regions Affected

England, Wales, Northern Ireland and S Scotland (remainder of Scotland is included in the WATCH)

Synopsis

Deep area of Low pressure "Olivia" (FU Berlin) drifts slowly across Ireland during Wednesday, dominating the weather across the United Kingdom.

Widespread showers and thunderstorms are forecast to develop across a large portion of the THUNDERSTORM threat area in response to daytime heating and increasing instability. Moderate-sized hail is possible in any stronger cells, and there is an increased risk of locally severe weather across the east/northeast of England during the evening hours with a threat of a moderate tornado. Locally high rainfall totals are possible from persistent, torrential downpours. Showers will also contain locally strong gusty winds.

Showers are forecast to progressively decrease in coverage during the second half of the evening hours, becoming largely limited to coastal regions.

http://www.ukasf.co....orecast/id-310/

[Ian Fergusson]

thanks for your ideas (-:

Chief Forecaster guidance from the MetO this morning highlights the huge MCS / supercell (his opinion) forming later today across the low countries. It'll give rain into eastern England but the primary action will remain over on the near continent - it will get wild there.

[Coast]

OK, a good day in store for some? (depending on your location in Northern Europe!)

Storm Forecast

Valid: Wed 14 Jul 2010 06:00 to Thu 15 Jul 2010 06:00 UTC

Issued: Tue 13 Jul 2010 22:54

Forecaster: PUCIK

A level 3 was issued for Benelux, small area of Northern France and extreme Northwestern Germany mainly for severe wind gusts, tornadoes, excessive precipitation and large hail.

A level 2 was issued for Southern to Central France, extreme Northwestern Switzerland and Southern Germany mainly for large hail, severe wind gusts and to the lesser extent for excessive precipitation.

A level 2 was issued for Western Germany, Denmark mainly for severe wind gusts, tornadoes, excessive precipitation and to the lesser extent for large hail.

A level 1 was issued for the regions surrounding the Level 2 mainly for severe wind gusts, large hail and excessive precipitation.

A level 1 was issued for England and Wales for tornadoes.

SYNOPSIS

The main macro-synoptic feature at mid levels will be a trough with axis over the Eastern Atlantic, with an embedded cold-core low centered over Ireland by Wednesday 12 UTC, moving slowly to northeast. Strong flow surrounds the fringes of the trough with windspeeds up to 40 m/s at 500 hPa level. A short wave trough will translate with this flow in the evening and early night hours over Northern France, Benelux countries towards Scandinavia. To east, a large ridge will stretch from the Central Mediterranean, across much of Central Europe into Northwestern Russia.

At the surface a centre of the deep low will reside close to or over the British Isles. Its trough will extend with the frontal system to the southeast and will accelerate quickly eastwards during the day. Mesoscale low will probably form within the frontal wave over Benelux and might become a significant factor in scenario. Ahead of the frontal system, high Theta-E airmass is advected at lower levels to northeast.

DISCUSSION

... France, Benelux, Western half of Germany ...

***Potentially dangerous setup with severe weather outbreak is forecast over this region***

Ahead of the frontal zone, high Theta-E airmass is advected at lower levels and as cooler mid-level temperatures overspread this airmass a belt of moderate latent instability is forecast to form. Models are in fairly good agreement regarding the CAPE values, which should be mostly in the range of 1000-1500 J/kg.

With strong southerly to southwesterly flow aloft, high values of wind shear are forecast, with over 25 m/s of DLS and 20 m/s of MLS, values sufficient for very well organised convection, including supercells. With weak relative upper level flow, convection will probably tend to organise into quasi-linear system rathern than into long-lived supercells. Another factor speaking for such system is the orientation of the mid and upper level flow to the boundary, which is almost parallel and therefore, quick clustering is expected. Nevertheless, the possibility of isolated, steadier supercellular convection, especially in the earlier stages of scenario can not be discounted.

Forcing should be very favorable, in the form of the cold front and as the above mentioned short wave trough , which might induce or support cyclogenesis in the axis of the frontal trough. Such low would probably contribute to the backing of the surface winds (increasing SREH values) ahead of it and to the strenghtening wind field at lower levels. Models simulate 30 m/s 700 hPa flow during evening and night hours in the proximity and behind of the surface front.

With such strong wind field at lower levels, quickly travelling mid-level short wave trough and strong tendency for storm clustering, severe quasi-linear MCS might travel at high speeds to northeast along the front and produce a swath of severe wind gusts, including some gusts over 32 m/s. This will be the prime threat and Level 3 is issued especially for the area, where the passage of severe MCS is most probable. In the earlier stages, when isolated form of convection will prevail and over the southern parts of Level 2, large hail will be a threat, especially if supercells form. In that case, hailstones over 4 cm might be observed. Especially to the northwest of the mesoscale low, excessive precipitation might occur, at the northern end of large MCS with possibility of "train effect". With high effective PW values, at least short term excessive precipitation can not be ruled out elsewhere in Level 2. Last, but not least, tornadoes might occur and more so in the environemnt with higher SREH and LLS ahead of the mesoscale low and lower LCLs during the late evening and night hours - therefore BENELUX and Northwestern Germany will probably be the region with the highest probability of tornado occurence. The fact that the convection will tend to occur mostly in linear clusters limits the potential for tornadoes

Nothing from TORRO yet, I expect something shortly.

Latest conditions:

[sbiggs]

Would agree with that forecast, Nick. Perhaps the potential for a severe threat a little further west, but best overlap of instability and vertical wind shear towards the east. An interesting forecast Skew-T for Cambridgshire from the 12z output:

From this sounding it would suggest conditions over this location and places further north look favourable for strong convective gusts and marginally large hail. Is an interesting setup indeed, and would think there's reasonable chance of some thunderstorms to have severe characteristics over towards that region.

sounds good although a novice at weather stuff, what does the graph mean, and now its closer the time, can you be more specific in cambs where this severe potential could be. I'm dead centre of cambs, and can travel. Will promise to get some pics and videos.

[sbiggs]

Oh I think I understand. So in a sense, the higher in the diagram, the higher the atmosphere, cause I cant remember the last time the surface pressure was under 950 let alone 100mb! That makes sense. As I have noticed these graphs quite alot where the lines pretty much are side by side and the wind "thingys" face that same direction in a blue colour, that would indict very stable conditions.

Am I also right in thinking the higher dew point, and more potential there is? Also do the green red and blue lines indicate anything, as well as the yellow numbers in the background of the graph?

[Neilsouth]

So humid , clouds did look thundery earlier too

[BrickFielder]

I looked out the this morning and thought hello we have some low level shear here today, which shows up on the overnight soundings. Looking out now and seeing all the high level cloud and I am not so optimistic.

I have also looked at various models and come to the conclusion that there are some significant discrepancies between the models so rather than look at what the models show I thought I would look at the satelite pictures today.

What I am seeing is a wave developing over northern France which somewhat changes the forecast. First we should see a warm front come through over the south eastern half of the UK followed by a quite sharp developing cold front. This is confirmed by the KNMI Satelite report today. Notice the thunder storm already developing over France to the east of this feature in the very humid air coming up from the south.

This does not neccesarily mean the risk of thunderstorms has diminished especially along that cold front. As for tornado risk then in some respects it is reduced as surface temperatures are unlikely to rise as forecast, but we also may have the prospect of a triple point crossing the UK. I am not sure how things will develop but I would expect some frantic activity and changes to forecasts soon. Notice also out to the west of this feature some fast moving lines of convection which when they meat the warmer temperatures inland could develop. Northern most storms in a line might be the ones to watch and in theory could produce a tornado, but seems unlikely at the moment. In conclusion then I doubt whether we shall see the low top supercells or severe storms, but the conditions might be ripe for a few surprises.

[Harry]

I looked out the this morning and thought hello we have some low level shear here today, which shows up on the overnight soundings. Looking out now and seeing all the high level cloud and I am not so optimistic.

I have also looked at various models and come to the conclusion that there are some significant discrepancies between the models so rather than look at what the models show I thought I would look at the satelite pictures today.

What I am seeing is a wave developing over northern France which somewhat changes the forecast. First we should see a warm front come through over the south eastern half of the UK followed by a quite sharp developing cold front. This is confirmed by the KNMI Satelite report today. Notice the thunder storm already developing over France to the east of this feature in the very humid air coming up from the south.

This does not neccesarily mean the risk of thunderstorms has diminished especially along that cold front. As for tornado risk then in some respects it is reduced as surface temperatures are unlikely to rise as forecast, but we also may have the prospect of a triple point crossing the UK. I am not sure how things will develop but I would expect some frantic activity and changes to forecasts soon. Notice also out to the west of this feature some fast moving lines of convection which when they meat the warmer temperatures inland could develop. Northern most storms in a line might be the ones to watch and in theory could produce a tornado, but seems unlikely at the moment. In conclusion then I doubt whether we shall see the low top supercells or severe storms, but the conditions might be ripe for a few surprises.

Sounds good to me BF!!

Cheers :lol:

[Nick F]

Interesting post Brickfielder re: frontal wave over Nern France, that will certainly slow the progress east of cold front. Certainly signs that thundery rain and embedded storms developing over N and NW france may edge a bit further west than models were anticipating and the next run may play catch up.

Cloud cover so far today rather extensive across England and Wales looking at visible satellite imagery, as the cold front moves NE and E, so this may hamper any great instability developing with lack of solar input. So chance of any severe storms with large hail and tornadoes developing have somewhat lessened. However, if we do gets some insolation, adjusting the 06z Larkhill (Wiltshire) radiosonde ascent earlier this morning just ahead of the cold front - by increasing temperature of a parcel rising from the surface from 15 to 21C and the dew point by a few degrees, some decent instability is likely to be released given some lift. Area of CAPE highlighted by yellow on the skew-t, the red line is the rising parcel. Notice too dry air intrusion at mid-levels which may further enhance potential instability, LCLs looks fairly low and winds are backing towards the surface. So a tornado potential just ahead of CF, with any strong instability that develops with insolation.

So still scope for some lively thunderstorms. Lack of solar insolation maybe offset by rather moist boundary layer and forcing likely to provided by cold front and ascent ahead of upper trough behind cold front. But if insolation is lacking we may not see the full potential instability realised.

Be interesting to see what the 12z ascents show later.

[Nick F]

12z Camborne and Brest radiosonde ascents suggest a fairly unstable post cold front rPm airmass, cloud tops to 400mb and 350mb respectively. Adjust the starting temp upwards by a few degrees with any insolation and there would be greater instability available. Low LCL heights may aid funnel tornado development with any wind convergence, some slightly drier air at 500mb and a saturated profile below may halp increase potential instability, though would want to see much drier air at 500mb for a tornado potential.

Thunderstorms certainly possible as evident across NW France and the west English Channel and also a few strikes showing over south Midlands, Liverpool Bay and numerous strikes across Ireland.

[Roger J Smith]

I'm thinking that tomorrow (Thursday 15th) may produce more widespread severe storm activity as the secondary plows into the current humid air mass. There are signs of tornadic potential and definitely a good threat for wind gusts, hail and torrential rainfalls on a larger scale than today, possibly the strongest severe outbreak since June 2007.

Would expect this to develop in multiple lines oriented NNW-SSE along and ahead of a front with the strongest storms likely to hit mid-day in the west Midlands to south central, later afternoon further east.

[Harry]

I'm thinking that tomorrow (Thursday 15th) may produce more widespread severe storm activity as the secondary plows into the current humid air mass. There are signs of tornadic potential and definitely a good threat for wind gusts, hail and torrential rainfalls on a larger scale than today, possibly the strongest severe outbreak since June 2007.

Would expect this to develop in multiple lines oriented NNW-SSE along and ahead of a front with the strongest storms likely to hit mid-day in the west Midlands to south central, later afternoon further east.

Music to my ears John Smith!

Just checked GFS and there is very little CAPE around, general well 0 in terms of LI also...not too sure about that tbh!

Edited July 14, 2010 by Harry

[Nick F]

I'm thinking that tomorrow (Thursday 15th) may produce more widespread severe storm activity as the secondary plows into the current humid air mass. There are signs of tornadic potential and definitely a good threat for wind gusts, hail and torrential rainfalls on a larger scale than today, possibly the strongest severe outbreak since June 2007.

Storms look unlikely to be as widespread as today across England and Wales from what I can see from model output - lapse rates become much weaker from the south during the morning, as warm front lifts north associated with the secondary low and cloud spreads NE with rain spreading NE across SW England and Wales by evening. Looks like there will be some scattered showers in the morning across many areas before dying out apart from over N England, but not the humdingers like today.

Scotland and N Eire looks a different story though - with steep lapse rates still up here, so some heavy showers or thunderstorms developing here, vertical shear looks rather weak however - so short-lived 'pulse' type storms the main mode - but still capable of torrential downpours, gusty winds and small hail.

[Coast]

OK, here's my round-up of what other people are saying or showing for today:

Storm Forecast

Valid: Thu 15 Jul 2010 06:00 to Fri 16 Jul 2010 06:00 UTC

Issued: Wed 14 Jul 2010 23:05

Forecaster: GATZEN

A level 1 was issued for south-western Scnadinavia mainly for tornadoes and severe wind gusts.

A level 1 was issued for the northern Allpine region, Czech Republic, and western Poland mainly for severe hail.

SYNOPSIS

At the periphery of a trough centred over the British Isles a strong south-westerly jet affects western and northern Europe. A negatively tilted short-wave trough moves northward into Scandinavia during the period while another short-wave trough crosses the British Isles. At lower levels, waves form along the frontal boundary over north-western Europe. To the south-east of this front, a warm and unstable air mass is present.

DISCUSSION

The Channel region and southern British Isles

Another short-wave trough yields a frontal wave across the Atlantic that travels into the British Isles on Thursday. Expect neutral lapse rates and rich low-level moisture in the warm air advection regime, some CAPE might build in response to diurnal heating. Latest model output does not indicate instability due to the warm air aloft and rather weak pre-frontal low-level moisture. However, at least a weak chance is present when the moisture increases from the west.

Along the occlusion of the wave that moves into the British Isles in the evening hours, a few embedded storms could develop. Given very strong low-level vertical wind shear in excess of 20 m/s in the lowest kilometre, tornadoes are not ruled out completely, and even strong tornadoes may be possible. Given the lack of instability predicted by the models, no level is given at this time.

Nothing yet from UKASF or TORRO

[Harry]

Looks like another risk of heavy, thundery showers and weak thunderstorms across parts of England and Wales tomorrow afternoon within post-frontal rPm airmass. As surface Low moves northward towards Scotland, steepening mid-level lapse rates and low-level moisture generates several 100j/kg CAPE across central, southern and eastern England by mid-late afternoon, and this should contribute to the development of heavy showers and perhaps some weak thunderstorms.

Into the evening showers or thunderstorms look to die away, but may still keep going across south-western, central-southern and south-eastern counties, with GFS modelling instability well into the evening close to these regions. Doesn't look to be any real overlap of sufficient vertical wind shear and CAPE, so at the moment would say severe threat is unlikely. However, given steep lapse rates, decent sized hail and gusty winds look to be the main threat in heavy showers and storms, and will be guided north-east with upper steering winds flowing from the SW.

The potential for a repeat of yesterday then (for southern areas) - some fairly scattered heavy showers and thunderstorms likely for many southern areas, combined with some gusty winds. Estofex seem quite convinced there is a risk of funnels/tornadoes, thus indicating the presence of some relatively decent sheer. Thus I wouldn't totally rule out the risk of one or two storms displaying some severe characteristics - after all, the E Kent supercell yesterday wasn't even inside Estofex's level 1 zone, yet as is quite common place down there, combinations of events can lead to some more intense cells, even if only for a relatively short time period.

Something to look forward to then potentially...good good

[Nick F]

Have issued a storm forecast for Friday, don't think there'll be any supercells Harry and far SE corner may miss storms with SW'erly flow this time, but isolated tornado not to be ruled out with any storm N and W of London:

Valid: 16/07/2010 00:00 - 17/07/2010 00:00

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

Synopsis

During Friday, a slow moving upper low over Scotland will drive a cyclonic SW'erly flow across the UK. At 00z, a low lying near Anglesey will move NE to lie near Fraserburgh, Scotland by 12z. Cold front lying S of low to Bournemouth will move E to clear SE England and E Anglia by 09z Friday. Then an increasingly unstable SW flow follows with trough lying Carlisle - Plymouth moving E and will be the focus for heavy showers with thunder to develop Sern UK in the afternoon.

... WALES, ENGLAND and E IRELAND ...

Isolated weak thunderstorms are possible across Irish Sea and Celtic Sea coastal areas into the early hours of Friday, as shortwave upper trough and surface low with wrap around occlusion move NE towards Scotland over the area creating forced ascent/convection of a moist boundary layer beneath steep lapse rates.

Otherwise, diurnal convection will develop during Friday in rPm airmass in wake of cold front clearing SE England and E Anglia in the morning. Greatest instability, and thus potential for t-storms, is likely to develop across S Wales, SW England, Midlands, Lincs and E Anglia - where richest low-level moisture will be beneath increasingly cold air arriving aloft as 500mb temps fall to -20C creating steep mid-level lapses resulting in modest MLCAPE values approaching 450-500 j/kg. With still some strength to the upper flow and 20-30 knts of deep-layer shear in the afternoon, storms may organise into multicells capable of producing isolated strong wind gusts, hail to marble size and torrential rain leading to localised flooding. Surface trough moving through over England in the afternoon may tend to focus heavy shower/t-storm development and its passage may create enough low-level shear for an isolated tornado not to be out of the question. Any storms will tend to die out after dark.

[Stuart]

And Today from UKASF

Storm Forecast Issued: 2010-07-16 01:00:00

Valid: 2010-07-16 00:00:00 - 2010-07-16 23:59:00

Regions Affected

Midlands, East Anglia, CS, SW & SE England, S & E Wales (remainder of Wales and majority of England is included in the WATCH)

Synopsis

Low pressure "Olivia" (FU Berlin) continues to dominate the weather across the United Kingdom on Friday, situated to the northwest of Scotland and allowing a rPm airmass to move across the country.

Scattered showers are forecast for the majority of the country, with the best environment for thunderstorms being across England and Wales - cloud heights will limit potential further north.

Across England and Wales the showers are expected to turn into thunderstorms by early/mid afternoon, with strong, gusty winds locally and a threat of a weak, or perhaps locally moderate, tornado. Hail up to 2cm in diameter is possible, particularly in showers along southern coasts during the evening.

Showers and thunderstorms are expected to decrease in coverage inland through the evening hours, but are expected to continue around coastal parts and perhaps over inland parts of Southeast England on the southwesterly wind flow

http://www.ukasf.co....orecast/id-311/

[Coast]

Some of the others picking up on this today.

ESTOFEX:

Storm Forecast

Valid: Fri 16 Jul 2010 06:00 to Sat 17 Jul 2010 06:00 UTC

Issued: Thu 15 Jul 2010 20:24

Forecaster: TUSCHY

A level 1 was issued for N-Italy, parts of Switzerland, Austria, the Czech Republic and SE/E Germany mainly for excessive rainfall and locally large hail.

A level 1 was issued for parts of France, Benelux and NW-Germany mainly for isolated large hail/severe wind reports and to a lesser extent for an isolated tornado.

A level 1 was issued for parts of Finland and up to the White Sea mainly for large hail, strong to isolated severe wind gusts and an isolated tornado event.

SYNOPSIS

A quasi-stationary low north of Scotland assists in persistent WAA downstream, so ridging over most parts of south/central and eastern Europe persists. A cold front runs from SW-France to NW-Germany and will produce showers/thunderstorms. Main activity regarding deep moist convection will be in the broad warm sector ahead of this boundary.

DISCUSSION

... France, Benelux and NW-Germany ...

Focus for showers/thunderstorms will be the slowly eastward moving surface cold front, as mid-levels atop that boundary cool down. Models still diverge in how well this overlap will be, but a concentrated swath (regarding space and time) with enhanced convection may evolve. Speed shear is strong (20 m/s at 0-3km and 25 m/s at 0-6km), so showers/thunderstorms may pose a severe wind gust/large hail threat. Despite weak directional shear signals in model data (0-1km layer), T-Td depression will be low and some LL CAPE evolves, so any deviant storm motion may cause enhanced helical inflow with an isolated tornado risk. This risk continues well into the night.

...United-Kingdom ...

Strong to isolated severe wind gusts may accompany showers/ thunderstorms in the highlighted area. LCLs around 600 m and some LL CAPE forecast, so an isolated funnel/tornado event can't be ruled out, mainly during the afternoon hours.

TORRO not on it yet.

Applicable charts etc:

Latest SatRep:

All eyes West this afternoon?

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

Friday looks interesting:

[The watcher]

Wednesday for Western areas looks interesting also.

[Stuart]

Here today from UKASF

Storm Forecast Issued: 2010-07-20 00:53:00

Valid: 2010-07-20 00:00:00 - 2010-07-20 23:59:00

Regions Affected

Yorkshire, Midlands, S + E Wales, SW England, W Northern Ireland (majority of the United Kingdom is included in the WATCH)

Synopsis

Shallow and complex area of Low pressure "Quendeline" situated over northwest United Kingdom will dominate the weather across the country on Tuesday.

Ahead of a very slow-moving, quasi-stationary cold front, a very warm and humid airmass is advected northwards from the south. As a result of daytime heating, instability is likely to increase across central and southern Britain, providing a focus for scattered thunderstorms.

Current thinking is that embedded thunderstorms will develop along the cold front, moving in a NNE direction along the cold front across central and southern parts of Britain. There is, however, some quite considerable disagreement as to the positioning of the cold front at any given time amongst the major models, providing a rather tricky forecast period. Nevertheless, there is a chance of a tornado to develop given favourable conditions, in which some embedded cells may exhibit some supercellular characteristics.

There is a chance of isolated/scattered thunderstorms to develop over the eastern English Channel during the evening, moving NNEwards during the latter hours of the evening and towards the end of the forecast period.

Across Scotland, Northern Ireland and Ireland, scattered showers and isolated thunderstorms are expected to develop in the returning Polar Maritime airmass later in the afternoon and during the evening hours. Here, hail to 1cm in diameter seems likely in many of the showers, and they will persist overnight, especially across Ireland, with a continued threat of thunder and lightning.

http://www.ukasf.co.uk/module-Storm/mode-forecast/id-314/