Convective Weather UK

[Nick F]

N-W storm forecast for today:

Valid: 09/08/2010 08:00 - 10/08/2010 06:00

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

Synopsis

Upper low and collocated surface low arrives across N Ireland and Scotland from the NW during the day, associated occluding front will move east across the UK, with troughs following across Nern UK in an unstable rPm W or SW flow.

… N IRELAND and SCOTLAND …

Upper low and associated cold upper air (500mb temps of -20C) overspreading N Ireland and Scotland from the NW during the day, behind front moving E, will create increasingly steep lapse rates aided by surface heating. As a result, instability is expected to develop in post frontal maritime airmass, with GFS modelling several 100 j/kg CAPE by 18z, so scattered heavy showers and thunderstorms are likely here. Strong upper flow and 40-50 knots of deep layer shear overlapping instability across N Ireland, in association with 100 knt+ jet streak, suggests organisation into multicell/line segement structures of any storms that develop here, and together with overlap of dry mid-level air, will enhance risk of strong convective wind gusts together with risk of hail. Low LCL heights, as low as 800m, along with increasing low level shear by evening ... suggests an isolated weak tornado cannot be ruled-out with any stronger updrafts - more particularly across N Ireland and SW Scotland. Also, large rainfall totals in a short space of time are possible with any storms, with risk of localised flooding. Have issued a SLIGHT risk for N Ireland and SW Scotland, with general thunderstorm area for the rest of Scotland. Any storms will tend to die out after dark.

[Nick F]

Convective / Storm forecast - Issued 09/08/2010 22:00

Valid: 10/08/2010 06:00 - 11/08/2010 06:00

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

Synopsis

Slow-moving upper low and collocated surface low over Scotland during Tuesday, with troughs around the low, will give an unstable flow across Nern UK.

… SCOTLAND and far N of ENGLAND …

Upper low and associated cold upper air (500mb temps of -20C) overspreading Nern UK during the day will create steep lapse rates aided by surface heating, with scattered heavy showers and isolated thunderstorms developing through the day. Upper flow and vertical shear will be rather weak, so no severe weather is anticipated. Any storms maybe accompanied by hail, gusty winds and localised torrential downpours. Weak flow, buoyant low-level updrafts and LCL heights below 1000m may be conducive for isolated weak tornadoes/waterspouts and funnels where likely wind convergence zones develop - particularly towards E Scotland. Any storms should die out after dark.

[Nick F]

Convective / Storm forecast - Issued 10/08/2010 22:00

Valid: 11/08/2010 00:00 - 12/08/2010 00:00

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

Synopsis

Slow-moving upper low and collocated surface low will be located just E of Scotland and NE England during Wednesday, occlusion moves SE across Scotland and into NE England.

… E SCOTLAND and NE ENGLAND …

Upper low and associated cold upper air (500mb temps of -20C) overspreading E Scotland and NE England during the day will create steep lapse rates with surface heating, with scattered heavy showers and isolated thunderstorms again developing through the day. Moderately strong upper flow circulating around upper low will create 30-40 knots of deep layer shear which will be sufficient for cell organisation into multicell storm clusters capable of strong wind gusts and small-moderate size hail. Also, 15-20 knots of low-level shear modelled to develop by early evening and low LCL heights may be conducive for tornadoes to develop with stronger, more buoyant updrafts into any storms, especially towards east coast of Scotland and NE England. Fairly high precipitable water (PWAT) values indicated by this evening's output suggests risk of torrential downpours leading to localised flooding, therefore issue SLIGHT risk for this area.

[Stuart]

well i hope i see something today nick i got my finger cross

Storm Forecast Issued: 2010-08-11 00:46:00

Valid: 2010-08-11 00:00:00 - 2010-08-11 23:59:00

Regions Affected

C, N, S + E Scotland, NE England and Yorkshire (Scotland and N + E England are included in the WATCH)

Synopsis

Low pressure "Xenia" (FU Berlin) continues to dominate the weather across the country on Wednesday, located over the North Sea.

Widespread scattered showers and thunderstorms are forecast to develop over many parts of Scotland and Northern England as instability increases.

Given the rPm airmass, hail is likely in many of the showers, and in stronger cells the hail may be moderate to locally large in size, accompanied by torrential downpours. There exists the potential for funnels or a weak tornado to develop. Showers will decrease in coverage during the evening hours, becoming mainly confined to the North Sea by the end of the forecast period.

http://www.ukasf.co.uk/module-Storm/mode-forecast/id-329/

[Coast]

and ESTOFEX back that up with:

Storm Forecast

Valid: Wed 11 Aug 2010 06:00 to Thu 12 Aug 2010 06:00 UTC

Issued: Tue 10 Aug 2010 22:30

Forecaster: PUCIK

A level 1 was issued for Eastern Spain mainly for large hail and severe wind gusts.

A level 1 was issued for a belt from Romania to Northern Russia mainly for large hail and to the lesser extent for severe wind gusts.

SYNOPSIS

Dominant macrosynoptic feature at midlevels will be a cyclonic vortex centered over the Northern Sea by Wednesday 12 UTC, surrounded by flow exceeding 20 m/s at 500 hPa. To the east, a ridge covers most of Eastern Europe and especially Russia, where unseasonably hot airmass has settled. Between these two features weak southwesterly flow will be observed.

Closer to the surface, a shallow low will stretch from the Nothern Sea towards Scandinavia and a ridge of high pressure will cover most of Central and Eastern Europe. Two frontal systems will become foci for thunderstorm development during the day. The first cold front will move across Western Germany and France during the day while the second will stall over Western Russia.

NE of Scotland today then?

[Stuart]

Thanks Coast good maps per all ways and looking at them I could maybe see a storm later in the day or missed out

[Nick F]

Forecast for Thursday:

Convective / Storm forecast - Issued 11/08/2010 22:00

Valid: 12/08/2010 06:00 - 13/08/2010 06:00

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

Synopsis

Slow-moving upper low over N Sea/Ern UK will slowly drift south, surface low over NE UK will move SE over N Sea and become slow-moving while wrap around occlusion over Nern UK drifts south in an unstable NW flow.

… S SCOTLAND, N ENGLAND, MIDLANDS, E ANGLIA and SE ENGLAND …

Upper low and associated cold upper air towards N and E UK over the last few days will shift slowly south towards more SEern areas during Thursday, so lapse rates will steepen/heights lower sufficiently for scattered heavy showers and isolated t-storms to develop more widely from southern Scotland south into SE England by the Thursday PM. Strongest wind shear will be over Wern UK while strongest instability will be towards Ern UK, so lack of overlap will not be conducive for a severe threat. However, 20-30 knots deep layer shear maybe just sufficient for some organisation of storms into multicell structures, particularly near trough/occlusion moving S, with storms capable of producing strong wind gusts and hail. Wind convergence zones developing towards eastern England maybe conducive for funnels and even an isolated weak tornado/waterspout cannot be ruled out.

[Stuart]

Storm Forecast Issued: 2010-08-12 01:23:00

Valid: 2010-08-12 00:00:00 - 2010-08-12 23:59:00

Regions Affected

East Midlands and East Anglia (NE England, Midlands East Anglia and SE England are included in the WATCH)

Synopsis

Low pressure "Xenia" (FU Berlin) continues to dominate the weather across the country on Thursday, located over the North Sea.

Scattered showers and isolated thunderstorms are forecast to develop over many parts of central, northern and eastern England as instability increases.

Given the rPm airmass, hail is likely in many of the showers, and in stronger cells the hail may be moderate in size, accompanied by torrential downpours. There exists the potential for funnels or a weak tornado to develop. Showers will decrease in coverage during the evening hours, becoming mainly confined to the North Sea by the end of the forecast period.

http://www.ukasf.co.uk/module-Storm/mode-forecast/id-330/

[Coast]

Someone's going to get something in the next couple of days surely? ESTOFEX think there may be a chance for eastern areas of the UK today:

Storm Forecast

Valid: Thu 12 Aug 2010 06:00 to Fri 13 Aug 2010 06:00 UTC

Issued: Wed 11 Aug 2010 17:30

Forecaster: GATZEN

A level 1was issued for north-eastern Spain mainly for large hail.

A level 1was issued for northern Italy, the Alps, central and eastern Germany, Czech Republic, western Poland, and southern Sweden mainly for excessive rain and large hail.

A level 1was issued for the western Ukraine, Belarus, and portions of western Russia mainly for large hail.

SYNOPSIS

A long-wave trough is centred over the North Sea. A mid-level jet curves around this trough from the Bay of Biscay to the west Mediterranean and further into the Baltic Sea and north-western Russia. Mid level jet streaks are expected over the British Isles, northern Iberia, and eastern Germany during the period. Warm air with steep lapse rates is present over most of eastern Europe and over Iberia. Ample low-level moisture can be found from northern Russia and Scandinavia across central Europe to the Mediterranean Sea.

I'll try and make these brief and small!!

[Stuart]

Good round up coast keeping my eyes on this today for here:D

[Nick F]

Convective / Storm forecast - Issued 12/08/2010 22:00

Valid: 13/08/2010 00:00 - 14/08/2010 00:00

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

Synopsis

A ridge of high pressure builds over the far NW with generally stable conditions here, while slow moving upper/surface low near E Anglia creates an unstable N/NW flow over eastern England during Friday.

… E ENGLAND, E MIDLANDS, E ANGLIA and SE ENGLAND …

Upper low and associated cold upper air centred near E Anglia on Friday will create steep lapse rates and unstable flow over the eastern side of England. Wrap around occlusion associated with low off E coast will drift SW early Friday, and will likely bring bands of convection over the N Sea onshore overnight into Friday morning moving inland, some of this convection may bring heavy downpours, hail, gusty winds and isolated lightning.

As solar heating increases during Friday so will CAPE, with several 100 j/kg developing towards the east beneath the cold pool in the afternoon, heavy showers and thunderstorms will develop inland across eastern and parts of central England through the day, aided by lift from occlusion and areas of vorticity circulating around the low. Any storms maybe accompanied by hail, cg lightning, gusty winds and torrential rain with risk of localised flooding. Vertical shear will be weak where greatest instability is likely to develop, so widespread organised severe weather seems unlikely. Low-level convergence towards E Anglia maybe conducive for funnels or even a weak tornado.

[Coast]

THERE IS A RISK OF THUNDERSTORMS FORECAST...

I'll see that and raise you:

Storm Forecast

Valid: Fri 13 Aug 2010 06:00 to Sat 14 Aug 2010 06:00 UTC

Issued: Fri 13 Aug 2010 06:07

Forecaster: TUSCHY

SYNOPSIS and DISCUSSION

Broad and quasi-stationary trough over the English Channel affects major parts of Europe and assists in widespread convection from the western/central Mediterranean all the way to Finland/Sweden. No major short wave is embedded in this SW-erly to southerly flow, so wind field features uniform speeds. This keeps shear values on the moderate side with 10 - 15 m/s DLS forecast. Also, BL air mass reveals only modest LL averaged mixing ratios, regionally enhanced by moisture pooling or numerous convergent stream line patterns, so MLCAPE will peak already between 500 - 1000 J/kg for most parts of the highlighted area. However, NE-Italy, Slovenia and Croatia will be an exception, where better moisture pushes CAPE to locally well above 1000 J/kg. Hence, this spot will see the highest threat for organized convection, producing large to isolated very large hail , strong to severe wind gusts and locally excessive rainfall amounts. In fact, the rainfall risk becomes more widespread over NW/N-Italy, whereas an isolated significant hail risk exists over parts of Slovenia and Croatia. A level 1 should cover that risk, although Croatia may be along a level 1/2 border, if indeed sufficient instability can build up. Areas in and north of Austria may see pulsating/multicell storms, regionally consolidating into long-lived clusters with heavy rainfall, isolated large hail and strong to isolated severe wind gusts. Right now, no corridor with enhanced severe is seen, so a level 1 mainly for the rain risk will cover all that for now. Models agree surprisingly well in a swath of heavy rainfall from S-Germany to the north during the evening and night hours, hence the level 1 was expanded well to the west. It's not yet clear how well GFS handles the wind field over E-Germany during the evening / the night hours due to the long-lived model QPF "bomb". Depending on the deepening rate of the depression over the Czech Republic, backing wind field would increase SRH1 and SRH3 values over E/NE-Germany. In fact, GFS 00Z places 20m/s LL shear with SRH1 around 400 m^2/s^2 at the NE-quadrant of the depression, which would indicate a substantial tornado risk, if surface based convection evolves.

Storm Forecast Issued: 2010-08-13 00:45:00

Valid: 2010-08-13 00:00:00 - 2010-08-13 23:59:00

Regions Affected

Yorkshire, E Midlands, East Anglia, CS + SE England (England, Wales and SE Scotland are included in the WATCH)

Synopsis

Low pressure "Xenia" (FU Berlin) continues to dominate the weather across the country on Friday, located over the southern North Sea.

Widespread scattered showers and thunderstorms are forecast to develop over many parts of central, southern and eastern England as instability increases.

Given the rPm airmass, hail is likely in many of the showers, and in stronger cells the hail may be moderate in size, accompanied by torrential downpours. There exists the potential for funnels or a weak tornado to develop. Showers will decrease in coverage during the evening hours, becoming mainly confined to coastal parts, with an indication of a distinct SW-NE line developing in the evening in the eastern English Channel, perhaps clipping coastal Kent/Sussex.

[Neilsouth]

PJB

Risk of Heavy Showers and Thunderstorms across England and Wales, Incl the following areas. NE England(This morning), Eastern England, East Anglia, London, SE England, Midlands, Southern Parts of NW England, SE England, CS England.

Synopsis

Upper level Cold pool and its spiral bands are moving slowly SSW across the Eastern Side of the UK, there is a mix of dynamic and convective precip. Strongest convection slipping SSW this morning in Eastern Parts and then developing from the Humber/Yorks SSE through Lincs the East Mids towards London and N Home COunties. This area will be under the deepest layer cold air this afternoon, combined with insolation - Mod CAPE can be released, 250j/kg+ of MLCAPE in eastern areas this afternoon, giving thunder, lightning hail and possible flash flooding ( as seen in Manchester yesterday) COnvergenze zone around the wash brings risk of a funnel cloud or two, though spot risk is prob less than 15%

Second zone develops over the NE Wales, West Midlands and fown into CS England with again heavy rain, scattered storms, though a little more movement in the cells here, meaning perghaps less risk of severe weather.

SW England, West Wales, N Ireland along with much of Scotland outside of the firing line today.

Tony Gilbert

9.50am Fri

Slight Risk Thundery Showers Central East & SE UK regions 09Z-21Z

A low end risk level primarily for scattered thundery showers. Occlusion slides south along eastern coast with a small pre frontal trough over the far SE. The forecast for convective development today is in the main, based on steep lapse rate potential and workable surface moisture advection. Convective box region is assisted by moderate mid level PV across the whole region throughout the day. Though vertical shear looks very poor indeed. I see the risk for funnel development no greater than yesterday with a distinct lack of moderate convergence/ conflunce and winds once again looking rather straight lined ATM.

Small risk of embedded convection W.Midlands through to Dorset. Though the risk here whilst marginally sheared is under saturation up to the trop. Hense CAPE values are unlikely to be truly realised.

A good target zone today might be around Kent and just south of the Humber

ukweatherworld

http://www.ukweatherworld.co.uk/forum/forums/thread-view.asp?tid=38420

[Tom Montalbano]

Certainly looks as though the thunder-starved London/S.E will see some thunder in the next 48 hours. To use a punting term,thundery showers/storms look a shoe-in to occur for this area with plenty of instability and zones of convergence setting up over parts of London and the S.E. Harry, Neil et al, enjoy, you've waited a long time!

Regards,

Tom.

[Neilsouth]

TORRO CONVECTIVE DISCUSSION 2010/013

A TORRO CONVECTIVE DISCUSSION has been issued at 10:00GMT on Friday 13th August 2010

Valid from/until: 10:00-2000GMT on Friday 13th August 2010 for the following regions of the United Kingdom & Eire:

E England

E Midlands

E Anglia

Central Southern England

SE England

THREATS

Hail 10-15mm diameter; wind gusts to 45-50mph; CG lightning; isolated tornadoes

SYNOPSIS

Slow-moving upper low and associated surface low are close to eastern England. Wrap-around moisture plume is moving SSW across eastern England. Lift associated with the cyclone, and diurnal heating, will produce numerous showers and a few thunderstorms. Flow is fairly weak, so organised severe weather is not expected. However, a few strong wind gusts are possible, along with hail in the stronger cores. In addition, a small tornado risk exists over parts of E Anglia, where some low-level cyclonically curved hodographs exist. Also, a convergence zone is progged close to the south coast for a time around the middle of the day, with an associated risk of a brief tornado.

Forecaster: RPK

http://www.ukweatherworld.co.uk/forum/forums/thread-view.asp?tid=38420

[Nick F]

Netweather storm forecast for Saturday;

Convective / Storm forecast - Issued 13/08/2010 22:00

Valid: 14/08/2010 06:00 - 15/08/2010 06:00

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

Synopsis

A ridge of high pressure affects the far N and NW with generally stable conditions here, while surface low near E Anglia moves SW overnight and Saturday morning, with associated occlusion, across SE England towards N France, with an unstable NE flow across England and Wales

… ENGLAND and WALES …

Broad upper low and associated cold upper air across England and Wales on Saturday will create steep lapse rates with surface heating in sunshine. As a result, widespread heavy showers and scattered thunderstorms are likely to develop across England and Wales through the day. Deep layer shear will be rather weak, generally 20 knots or less - so no organised severe weather is expected. Given fairly light upper winds, storm motions will be fairly slow - and given several 100 j/kg CAPE modeled, slow-moving torrential downpours will likely develop which may lead to localised flash flooding. Also any storms maybe accompanied by hail, cg lightning and gusty winds. Local wind convergence zones developing, more particularly across central-S England and NW England will be conducive for funnel development and a weak tornado cannot be ruled out with stronger more buoyant updrafts, particularly given low LCL heights and plenty of SBCAPE.

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

[Coast]

THERE IS A RISK OF THUNDERSTORMS FORECAST...

Excellent!

ESTOFEX following your thinking Nick with a level 1 over the South:

Storm Forecast

Valid: Sat 14 Aug 2010 06:00 to Sun 15 Aug 2010 06:00 UTC

Issued: Sat 14 Aug 2010 05:53

Forecaster: VAN DER VELDE

A level 2 was issued for N Italy, S Austria and Slovenia mainly for excessive convective rain, as well as severe wind gusts and tornadoes.

A level 2 was issued for W Poland and level 1 for parts of Lithuania, Czechia, Slovakia, Hungary, Croatia and Serbia mainly for large hail and severe convective wind gusts.

A level 1 was issued for England and NW France for water/landspouts.

A level 1 was issued for northern Scandinavia mainly for severe convective wind gusts and enhanced tornado potential.

SYNOPSIS

With a large upper low over western Europe, centered over the English Channel, a warm humid airmass is transported northward from the Mediterranean to central Europe. During this period it will cause rainy and thundery conditions around the surface low over northern Italy and the south side of the Alps. Very unstable air is in place in central Europe. Weaker unstable air is present under the upper trough over France and UK, and over Scandinavia.

...England and NW France...

The upper trough and weak surface winds provide convergence zones with high vertical vorticity which can be spun up by convective updrafts in the humid airmass (e.g. 00Z Herstmonceux, Trappes, Camborne, De Bilt soundings) while not being disturbed by vertical shear or mixing/entrainment of the superadiabatic surface layer. Land/waterspouts and funnel clouds are therefore likely.

UKASF also broadly in agreement:

Storm Forecast Issued: 2010-08-14 00:58:00

Valid: 2010-08-14 00:00:00 - 2010-08-14 23:59:00

Regions Affected

Midlands, Home Counties, E Wales and SE, CS + SW England ( remaining areas of England and Wales are included in the WATCH )

Synopsis

A shallow area of Low pressure over northern France will dominate the weather across the country on Saturday.

Widespread scattered showers and thunderstorms are forecast to develop over many parts of central, southern and eastern England as instability increases during the morning, these moving in a (on average) southwesterly direction into SW England and Wales during the afternoon.

Given the rPm airmass, hail is likely in many of the showers, and in stronger cells the hail may be moderate to locally large in size, accompanied by torrential downpours. There exists the potential for funnels or a weak tornado to develop. Showers will decrease in coverage from the northeast as a ridging occurs, with virtually all parts dry by the end of the evening.

It's everywhere according to the USAF!:

and UKMO

Very messy:

Not good for Eastbourne Airborne, but if it's going to rain, at least lets have a storm!!!

[Coast]

We seem to miss out today but cast your eyes to the SE across the Channel and a rare level 2 a couple of hundred miles away from ESTOFEX:

...Benelux...

Serious rainfall risk may evolve with gradually deepening vortex and evolving deformation zone just over Belgium and the Netherlands. Inflow into this deformation zone features deep and very moist air mass with intense lift. Prolonged period of near quasi-stationary conditions of strongest convergent flow and aforementioned air mass quality rise the concern of widespread excessive rainfall. It's not yet clear, where strongest banding occurs, so the level 2 is still quite coarse. New model data may increase confidence later-on, where highest rainfall amounts occur

Zeebrugge ferry would get you into the thick of that today....... (although GFS has it further SE so you would need to travel!)

[Coast]

Nothing from ESTOFEX unless you're in East Germany, likewise Nothing from UKASF and the charts say:

Doesn't look encouraging today I'm afraid!

[Coast]

Some interesting output for tomorrow, mainly concerning central and eastern England during mid-late afternoon period.

After yesterdays little disturbance caught a few out, what does the run of the other web information have to say about today?

Storm Forecast

Valid: Wed 18 Aug 2010 06:00 to Thu 19 Aug 2010 06:00 UTC

Issued: Tue 17 Aug 2010 21:12

Forecaster: KOROSEC

SYNOPSIS

A large trough centered over north-western Europe remains quasi-stationary. Embedded in this trough, an elongated upper low from British Isles moves towards the North sea. A weak upper low over extreme SW Europe makes only slow progress towards NE where it is expected to merge with the main trough on Thursday.

At surface, a frontal system across eastern Europe pushes towards western Russia, where both cold and northwards advecting warm front are focus for convective activity. Another (strong) cold front enters NW Russia from the north and merges with the southern frontal system overnight to Thursday.

UKASF are on holiday (no really!!) and TORRO have nothing, so here are some nice pictures to cut out and put in your album or the bedroom wall.....

I'm tempted more by North East Anglia, late afternoon, but it's not cut and dried by any means.

[Nick F]

Net-Weather storm forecast for today:

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

[Coast]

Now this is a little more encouraging!! NW forecast with ESTOFEX having almost all of usunder a level 1!

Storm Forecast

Valid: Fri 20 Aug 2010 06:00 to Sat 21 Aug 2010 06:00 UTC

Issued: Fri 20 Aug 2010 05:15

Forecaster: SCHLENCZEK

A level 1 was issued for UK and Ireland mainly for tornadoes and severe wind gusts.

A level 1 was issued for parts of France, Switzerland and Italy mainly for excessive rainfall.

SYNOPSIS

The main feature for organized convection on Friday is a strong low pressure system over the Irish Sea, moving to the NNE towards N Scotland during the period. Its cold front stretches from NW Scotland towards SE Ireland on Friday 06 UTC and will cross the British Isles until the late evening. A 50 m/s southwesterly jet streak points from the East Atlantic towards Scotland with an embedded shortwave trough in the vicinity of the cold front.

Another upper trough is centered over northern Russia but its influence w.r.t. convection will be marginal as CAA stabilizes the lower troposphere over most portions of eastern Europe. Between both low pressure sytems, an upper ridge has established over south-central Europe. Some thunderstorms are expected in the Alpine region and over central France and Italy in a weakly sheared environment.

...UK and Ireland...

In the vicinity of the cold front, some low-end instability is in place with strong shear at all levels (15 m/s LLS, 20 - 25 m/s DLS). 03953 00Z sounding shows an almost saturated thermally neutral layer from 750 hPa to 300 hPa and SFC T/Td difference close to zero. There is a capping inversion in the lowest 200 hPa which tends to disappear when the dry slot arrives. The 03918 Castor Bay 00Z sounding is similar and points out that a very moist and slighly unstable airmass overlaps with intense LL shear and locally enhanced SRH. Current thinking is that this setup may allow several tornadoes over UK and Ireland, especially in the northern part of Ireland and Scotland where the temperature gradient near the cold front is maximized and upper level winds are perpendicular to the frontal boundary. Another important threat will be severe wind gusts as low level winds already reach values near 20 m/s. .

UKASF still on holiday (they will miss out!!) and TORRO have one from last night and an update as follows:

TORNADO WATCH 2010/005

A TORRO TORNADO WATCH has been issued at 0700GMT on Friday 20th August 2010

Valid from/until: 07:00- 20:00GMT on Friday 20th August 2010 for the following regions

Parts of (see map)

Wales

Much of England

Northern Scotland

THREATS

Tornadoes; wind gusts to 65mph; CG lightning; heavy rain

DISCUSSION

Reference TW004 below for main synoptic overview. Short-wave trough is moving towards SW Wales. Strong ascent ahead of this has allowed thunderstorms to develop from the moisture plume. Although these may be slightly elevated some surface based activity is likely. Tornadoes are possible, perhaps strong, along with severe wind gusts as it moved north-east. Further activity may then develop from the shallow moist zone, if spells of sunshine can develop. Again, severe winds and isolated tornadoes are possible.

TORNADO WATCH 2010/004

A TORRO TORNADO WATCH has been issued at 2315GMT on Thursday 19th August 2010

Valid from/until: 23:15- 08:00GMT on Thursday 19th/Friday 20th August 2010 for the following regions

Parts of (see map)

Eire N Ireland S Scotland Isle of Man

THREATS

Tornadoes; wind gusts to 65mph; CG lightning; heavy rain

DISCUSSION

Strong upper low is moving NE to the west of the British Isles, with an associated short-wave crossing the watch area. A broad, very moist tropical maritime airmass exists at low levels, behind a warm front, which is currently moving through Scotland. A cold front to the west of Eire/N Ireland will start to move eastwards later tonight, and tend to surge eastwards later. Instability exists in the warm sector, partially aided by mid-level cooling associated with the upper trough. Thunderstorms are occurring already across SW Eire, and further showers and a few thunderstorms are likely overnight. Strong deep layer shear (40-50 knots) should promote cell organisation, perhaps supercells. Low-level shear of 25-30 knots suggests low-level mesocyclones are possible. Tornadoes and damaging winds are possible across the area, and the magnitude of the low-level shear coupled with a very moist boundary layer suggests a small chance of a stronger tornado.

The risk will extend into Scotland through tomorrow morning, and a new watch is likely to be needed tomorrow morning.

Nice!!!!

and as Nick has shown in the discussion thread:

Dew points already high this morning:

[Stuart]

yes coast thee maps look good for me later on and 2night

[Coast]

Another level 1 today from ESTOFEX???!

Storm Forecast

Valid: Sat 21 Aug 2010 06:00 to Sun 22 Aug 2010 06:00 UTC

Issued: Sat 21 Aug 2010 05:18

Forecaster: VAN DER VELDE

A level 1 was issued for southern UK (and to a lesser extent central Sweden) mainly for a chance of tornadoes and excessive convective rain.

SYNOPSIS

On the south side of a low pressure area between Scotland and Norway a strong WSWerly flow advects a warm and very humid airmass concentrated in a stationary frontal band. Over Scandinavia this curls back into a secondary low pressure center over central Norway and moves into Finland as warm front. In most of the region convection is barely surface-based, or capped today, and reaches EL at temperatures between a warm -20° and -30°C. Over central Scandinavia tops are colder.

With very low LCL, high moisture content and low CAPE, convection will be mostly rainy rather than thundery.

A trough in mid levels passes over central Italy.

DISCUSSION

...southern UK...

This area is not capped in GFS, shows a good deep convergence signal, and is in a strong shear regime, about 20 m/s DLS and more than 10 m/s LLS. GFS hints at a wave in the front. The main mode of convection is thought to be one or more training lines (streets), with an embedded possibly tornadic mini-supercell not ruled out. In the moist environment rain sums could locally become high, provided a decent amount of convection indeed forms. Rather strong but probably not severe gusts are likely.

Well dew-points are very high again today, what do UKASF say?

Storm Forecast Issued: 2010-08-20 20:38:00

Valid: 2010-08-21 00:00:00 - 2010-08-21 23:59:00

Regions Affected

Wales, Midlands, East Anglia and SW England (the remainder of England and Wales, and NW Scotland is included in the WATCH)

Synopsis

Low pressure "Angelika" (FU Berlin) situated to the north of Scotland will dominate the weather across the United Kingdom on Saturday.

To the south of a waving cold front, a warm and very humid airmass is advected across central and southern Britain. Embedded convection is forecast to develop along the front across SW/C-Britain, providing a focus for scattered thunderstorms. The environment in which these will/may develop looks quite favourable for severe development, with a chance for moderate-size hail, and a moderate-intensity tornado possible. However, due to the uncertain extent of thunderstorm coverage, only a THUNDERSTORM threat level has been issued at this stage, but may be upgraded during Saturday. Any storms that do develop will move in a NE direction along the front.

Across NW Scotland, scattered showers in the rPm airmass pose a low threat (20% chance) of thunder and lightning.

Lower to middle half of the country today? Perhaps Bristol Channel through to London and out into East Anglia later? I think I'm out of the zone but happy to watch it develop for you guys!

[Coast]

Here's what the others are saying about today into tonight:

Storm Forecast

Valid: Sun 22 Aug 2010 06:00 to Mon 23 Aug 2010 06:00 UTC

Issued: Sun 22 Aug 2010 05:36

Forecaster: TUSCHY

A level 1 was issued for parts of the UK, Belgium, the Netherlands, Luxembourg, parts of France and Germany, parts of Poland, parts of Belarus, Lithuania and Latvia mainly for large hail, severe wind gusts, a few tornadoes and heavy rainfall.

SYNOPSIS

Brisk SW-erly flow has established over N-Europe with a quasi-stationary SW-NE elongated vortex north of Scotland. Numerous waves, embedded in this flow regime, cause regionally enhanced thunderstorm chances. Hot and stable conditions prevail over the Mediterranean and parts of SE-Europe.

DISCUSSION

UPDATE 00Z

Since midnight, a trailing stratiform MCS evolved over the Bay of Biscay and moved rapidly to the ENE and onshore along the W-coast of France. Numerous 20-23 m/s wind gusts were reported. This activity was fostered by a first upper wave over the English Channel, but thunderstorms are now on a downswing. Another wave is about to enter the English Channel (06Z) and it ought to increase thunderstorms again over France during the upcoming hours. Those models, which analyze current convection with at least modest success all evolve an organized cluster over central Germany during the afternoon hours. Hence confidence increases that a swath of strong to severe wind gusts could indeed evolve from central to east Germany/west Poland.

Storm Forecast Issued: 2010-08-22 01:02:00

Valid: 2010-08-22 00:00:00 - 2010-08-22 23:59:00

Regions Affected

East Anglia + SE England (Scotland, Northern Ireland, Midlands + SW/CS England are included in the WATCH)

Synopsis

Low pressure "Angelika" (FU Berlin) situated to the west of Scandinavia will continue to dominate the weather across the United Kingdom on Sunday.

To the south of a waving cold front, a warm and very humid airmass is advected across far E/SE England. Embedded convection is forecast to develop along the front across East Anglia/SE England, particularly during the afternoon, providing a focus for isolated/scattered thunderstorms. Any storms that do develop will move in a ENE direction along the front, and pose a threat of a tornado.

Across Scotland, Northern Ireland and Eire, scattered showers in the rPm airmass pose a low threat (30% chance) of thunder and lightning.

TORRO have yet to renew their watch for Southern England today, keep an eye on here for that a bit later