Convective Weather UK

[Nick F]

Showing it on their TS threat output, but it's a tiny corner over me late evening/early Saturday

Clutching straws now, we know it'll shift east :lol:

[Coast]

Clutching straws now, we know it'll shift east

I am - do I sound desperate Nick?

Actually one question: Does my memory deceive me or is this a quiet year for thunderstorms so far?

[Nick F]

Actually one question: Does my memory deceive me or is this a quiet year for thunderstorms so far?

It's been pretty poor I think, well for here at least anyway.

Early Saturday does show potential from UKMO for some heavy thundery rain/perhaps storms across far SE as a wave develops along cold front moving east Friday - as unstable airmass moves N out of France. Though chances are that the wave may not develop so we just end up with bog standard rain.

looks quiet on the storm front elsewhere for the moment at least.

[ZONE 51]

NAE show ppn heading towards the SE at thursday night into friday morning , ukmo show a trough develop ahead of the cold front could this turn thundery ?

GFS dont seem to show ppn this far east at the time the NAE chart is showing ppn further east

[staplehurst]

Tonight's FAX from the UKMO now sides with the GFS - the storms stay on the continent in the Low Countries on Friday night!

Quite surprised to be honest, considering the consistency from the FAX's since Sunday evening.

[Thundery wintry showers]

I am - do I sound desperate Nick?

Actually one question: Does my memory deceive me or is this a quiet year for thunderstorms so far?

It's been pretty poor I think, well for here at least anyway.

We'll have to see how the Met Office's ATD lightning map for June turns out when they publish the June summary, but I strongly suspect that you're both right. Certainly the spring had unusually low thunder activity, and I don't think June has seen any catching up- just average at the very most.

Norwich, plus Cleadon in Tyne and Wear, have both had 2 thunder-days so far this year. The Cleadon figure isn't outstandingly low for this point in the year, but the Norwich one certainly is.

[Coast]

ESTOFEX showing what the French and Dutch will get today:

Storm Forecast

Valid: Fri 02 Jul 2010 06:00 to Sat 03 Jul 2010 06:00 UTC

Issued: Thu 01 Jul 2010 20:05

Forecaster: TUSCHY

A level 1 was issued for large hail (an isolated significant event possible), severe wind gusts, excessive rainfall and to a lesser extent for tornadoes over N-Spain, parts of France, Belgium and the Netherlands.

SYNOPSIS

An omega-like pattern gets established over Europe, with one major upper trough over Ireland/UK and Scotland and another one further to the east over W-Russia and Belarus. In-between, strong ridging builds north/northeastwards during the forecast period with hot temperatures spreading from SW-Europe to central Europe.

DISCUSSION

... N-Spain, France, Belgium and the Netherlands ...

From a synoptic point of view, the mover for thunderstorm initiation is an upper trough over UK/Ireland and Scotland. This feature amplifies furthermore during the forecast period, as a 60 m/s speed maximum at 300 hPa dives into the upstream side of that trough. A sharp cyclonic kink in high-level streamline pattern evolves over the Bay of Biscay, as favorable exit/entrance pattern gets established. This scenario has some effects further downstream over France, as WAA intensifies once again with rising geopotential heights forecast by all models. It is a bit hard to determine a single forcing mechanism, as eastward traveling vorticity lobe gets stretched in a SW-NE fashion over the Bay of Biscay and NW-France with probably better forcing available after sunset, as a potent short wave enters the Engish Channel from the west and traverse east/northeastwards. Therefore, a broad area will see adequate forcing for initiation with most widespread thunderstorm coverage building from Spain/S-Bay of Biscay northeastwards during the afternoon hours onwards. At the surface, a weak front moves in from the NW and affects NW/N-France after sunset in accord with best mid-/upper level lift, so confidence is high for scattered to widespread thunderstorm initiation during the evening and night hours.

CAPE fields are once again impressive over France and there are a few reasons to buy into that scenario. As the upper low amplifies, winds at all levels continue to back to a more southerly direction and therefore, a thick EML is able to spread from Spain to the north/northeast during the day. Yesterday at 18Z, surface dewpoints over S-France ranged between 15-22°C and keeping in mind that additional moisture from the Mediterranean may surge to the north and latest surface moisture analysis from the top 2 m surface layer reveals a modest positive bias over S-France, confidence exists for dewpoints in the upper tens over S and central France. Also, the moist surface layer ought to increase in depth, precluding daytime driven mixing (at least not comparable to the past few days). Further to the west and north, moisture pooling along the incoming front may also keep dewpoints well above 16°C, so we expect a warm sector, characterized by 800 to 1500 J/kg MLCAPE with locally higher maxima well possible. Despite ongoing WAA, intense diabatic heating helps to keep CIN values quite low over the warm sector.

Shear will be a limiting factor for widespread thunderstorm organisation in the warm sector. DLS increases to 15 - 20 m/s over W-/ N France, the Netherlands and Belgium with somewhat weaker 0-3 km shear. Nevertheless, directional shear is enhanced in the 0-1 km and 0-3km layers and some overlap of kinematic/thermodynamic fields may yield a favorable environment for organized storms along the front itself.

To summarize all that, we expect thunderstorm initiation already during the late morning hours from N-Spain all the way to the Netherlands, but more isolated to scattered in nature. Nevertheless, well organized multicells/isolated supercells are possible with an attendant large hail and strong wind gusts risk. Further east, over central/eastern France, a few thunderstorms may evolve during the peak time heating (afternoon hours) with abundant CAPE, weak shear and a very dry/mixed subcloud layer. Hence, isolated large hail and locally severe downbursts remain the main hazard, but too isolated for a level 1. Later on, during the evening hours, thunderstorms over N-Spain and SW-France increase in coverage and intensity, moving to the northeast. During the initiation stage, large hail (an isolated significant event is possible) and strong wind gusts remain the main hazard. Betimes, probably numerous thunderstorm clusters move over W-France northeastwards with an heavy rain, severe wind gusts and marginal hail risk. Also, an isolated tornado event is possible, given increasing LL directional shear and lower LCLs along the front itself. This activity also affects Belgium and the Netherlands during the night/morning hours. We decided to stick with a level 1 for now, as final moisture return and placement of the boundary remain a bit uncertain, but an upgrade may be performed later the day, if a more concentrated swath of severe events looks probable.

UKASF say extreme SE in the watch area:

Storm Forecast Issued: 2010-07-02 00:53:00

Valid: 2010-07-02 00:00:00 - 2010-07-02 23:59:00

Regions Affected

(Kent and East Sussex are included in the WATCH)

Synopsis

A very large and deep area of LOW pressure over the North Atlantic will dominate the weather across the United Kingdom on Friday.

An eastward-moving cold front will cross England during the period, becoming increasingly weak. Ahead of the cold front, very warm and unstable air is advected northeastwards from Spain across France and BeNeLux. Destabilisation of this airmass is expected to occur during the afternoon and in particular the evening and overnight.

Thunderstorms, locally severe, are forecast on the continent. There is a chance of a few thunderstorms perhaps grazing the extreme southeast corner of the country as they develop, ahead of the weak cold front, over the Channel during the evening hours, moving in a northeast direction. The greatest chance of this occuring appears to be 22z - 03z on Friday night, although the risk is currently very low.

We will monitor the situation throughout Friday.

What do the charts show?

Current conditions:

It's touch and go tonight. TBH I'd pick a high spot overlooking the Channel (Beachy Head for me) and watch the action out to sea as I'm not convinced it will make land here.

[Harry]

Agreed...I am so bitterly jealous though...as per the norm, we have a number of ingredients though missing a 'critical' cog in the timepiece...we have the heat, we have the humidity and the dew points, we have the solar heating, but we lack (of all things to lack over this poxy Island) lapse rates and cool air aloft....so far this year, we have had cold uppers and pitiful attempts at Cbs trying to build up, but have been feable either due to lack of solar heating, lack of moisture, lack of heat...really not sure I can take much more of this place to be honest...

On a positive note, does look like we'll see some lightning across the SE tonight, all be it in the form of a flashing horizon and flickering starry skies as opposed to anywhere near close by!! Part of me is tempted to grab the other half and head down to our caravan in Dymchurch tonight...it's likely to be warm plus should give some fairly decent views of the storms moving up Benelux!

[Nick F]

It's touch and go tonight. TBH I'd pick a high spot overlooking the Channel (Beachy Head for me) and watch the action out to sea as I'm not convinced it will make land here.

You wear out my mouse wheel the way you post your charts! Any way you can post the same charts as thumbnails like this if have lots of them?:

[Coast]

Any way you can post the same charts as thumbnails like this if have lots of them?:

Hot-links, resized automatically Nick, I'll try and upload them next time. If not, I'll send you a new mouse... (my eyes are getting older!)

What do you think about seeing the activity from this side of the Channel?

[Nick F]

Hot-links, resized automatically Nick, I'll try and upload them next time. If not, I'll send you a new mouse... (my eyes are getting older!)

What do you think about seeing the activity from this side of the Channel?

Sorry, not trying to tell you what to do, just trying to find what you've typed amongst the charts - just me being too lazy to scroll Must admit it is more visible the way you post them, rather than clicking on thumbnails to see them.

Looks like an East Kent Klipper potential later this evening. If I wasn't going to London this evening, i'd probably head down to Dymchurch like Harry, or further east to the White Cliffs to catch some lightning.

[Harry]

Sorry, not trying to tell you what to do, just trying to find what you've typed amongst the charts - just me being too lazy to scroll :unsure: Must admit it is more visible the way you post them, rather than clicking on thumbnails to see them.

Looks like an East Kent Klipper potential later this evening. If I wasn't going to London this evening, i'd probably head down to Dymchurch like Harry, or further east to the White Cliffs to catch some lightning.

I agree with Nick - I think the Kent/Sussex coast could be in for a chance tonight...some early cells have broken out across W/C France and moving NE, but along the front in a similar area, and even further south than that, there is a more northerly push away from NE...if any cells fire across NW France, these could make landfall...slim chance but better than no chance IMO.

[Coast]

I agree with Nick - I think the Kent/Sussex coast could be in for a chance tonight

Still touch and go for me!

[Nick F]

Still touch and go for me!

A look at the Trappes (Paris), France 12z sounding shows quite unstable mid-upper profile with 1270 j/kg of CAPE, makes you want to weep! Cloud tops would probably reach 40,000ft given enough lift.

[ZONE 51]

a risk for thunder n-ireland and parts of scotland on sunday? with negative li/ some cape

[ZONE 51]

i wont get excited yet this time , but GFS does show some impressive energy here , MCS going through kent most likely at this stage but 4 days away things can shift east , but i cant see much thats going to move it east much more , i think this is our best chance out of all the close shaves so far this season .

[Nick F]

Tomorrow looks quite interesting across Ireland, a surface low tracking NE with cold front moving E behind a warm moist Tm airmass, overlaid by the left exit area of a strong Atlantic jet streak.

Storms are possible across Ireland as the warm moist air destabilises near low/along cold front, GFS shows several 100 j/kg SBCAPE around he middle of day. Any storms that form will be in an environment of fairly strong deep layer of 40-50 kts and strong low-level shear too, due to change of wind direction with height near the low - so potential for storm organisation - maybe a supercell or two and a risk of a tornado, as suggested by Lightning Wizard's Sig. Tornado Parameter:

Limiting factor for a tornado is lack of mid-level dry air intrusion suggested by GFS, with quite a saturated profile.

Also some storms may develop over southern Scotland too Saturday night as the stronger forcing arrives from the west overnight into Sunday, though severe potential lessens after dark.

Otherwise looks like the rest of us may have to wait for next week for some shaky hope of a storm. Possible MCS moving north out of France early on Monday may clip the SE/E Anglia. Some more widespread storm potential showing on Thursday - as low pressure moves in across the UK, but alot of model divergence this morning for latter half of next week.

[ZONE 51]

TORRO CONVECTIVE OUTLOOK issued on Friday July 9 2010.

A broad upper trough to the west of the British Isles will sharpen as it approaches during the next 36-48 hours. A frontal wave will develop in response to this, and deepen into a surface depression, which is then progged to track NNE through western Eire and into western Scotland through Saturday.

Close to the track of the depression, weak instability is expected to develop in a fairly strongly sheared environment. Cloud will be rather extensive but any breaks will allow somewhat larger instability to develop locally across Eire and N Ireland.

An extensive area of rainfall will accompany the frontal system across Eire, N Ireland and Scotland, although a few embedded thunderstorms are expected too. The highest risk of severe weather appears to be across Eire/N Ireland, where isolated tornadoes and damaging wind is possible. A lower risk for Scotland, N Wales and N England, but this could increase through the evening.

The extensive cloudiness associated with the warm sector (tropical maritime origin) along fairly neutral lapse rates currently indicate the overall risk is fairly low. However, the situation will be monitored tomorrow, and if cloud breaks more than currently expected in the warm sector, the overall risk would likely be somewhat higher.

Forecaster: RPK.TORRO

[Stuart]

and for Today

Storm Forecast Issued: 2010-07-11 01:02:00

Valid: 2010-07-11 00:00:00 - 2010-07-11 23:59:00

Regions Affected

SE England (CS England, East Anglia and the northern half of Scotland are included in the WATCH)

Synopsis

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

During the early hours there is a chance of scattered convective activity amongst showers moving northeastwards across Scotland and the North Sea, though this risk decreases rapidly towards dawn.

Attention then turns to the English Channel and nearby continent during the evening hours. Scattered showers and thunderstorms are forecast to develop over the eastern English Channel as destabilisation occurs of the very warm and humid airmass present over eastern England and the majority of the continent. These showers/storms will then move northeastwards into parts of Southeast England by the very end of this forecast period.

These showers/storms are expected to be elevated in nature, and so severe weather is unlikely. However, hail up to 2cm in diameter is possible.

Showers or spells of rain are forecast to develop across other parts of southern England during the evening, though these are unlikely to exhibit thunder and lightning due to unfavourable conditions.

http://www.ukasf.co.uk/module-Storm/mode-forecast/id-308/

[Coast]

and for Today

Yep, just clocked that Stuart. :wacko: Perhaps I could just add the following (sorry for the size Nick, hotlinked!) for consideration of anything today:

Storm Forecast

Valid: Sun 11 Jul 2010 06:00 to Mon 12 Jul 2010 06:00 UTC

Issued: Sun 11 Jul 2010 05:45

Forecaster: SCHLENCZEK

A level 1 was issued for E France, Benelux, W-central Germany, W Austria, N Italy and Switzerland mainly for excessive precipitation and to a lesser extent for large hail and severe wind gusts.

SYNOPSIS

An unstable airmass with 1000 - 2000 J/kg MLCAPE covers large portions of western / central Europe. Some mid-level vorticity advection is forecast for western / central Germany during the afternoon hours, leading to a convergent flow at lower levels as shown by 10m / 925 hPa wind maps. Later in the evening, the vort-max of an upper shortwave trough will reach western France.

The other zone of moderate instability but very weak vertical shear is expected over SE Europe from W Russia, Ukraine and Belarus towards Romania.

DISCUSSION

...E France, W Germany, Benelux...

A zone of deep convergence should be present over eastern France and central Germany in the late morning / early afternoon hours. The cap should be relatively weak in both regions with strong mid level convergence as shown by a very small LCL - LFC difference. Recent soundings show 10 - 15 m/s winds around 6 km AGL which is slightly more than predicted by GFS. The directional shear is rather disorganised in most soundings but nevertheless there are some small spots of slightly enhanced SRH3 forecast for N- central Germany in the afternoon hours. According to the thermodynamic and kinematic environment, the development of multicell storms should be most likely. These storms may produce isolated large hail and isolated severe wind gusts but the main threat will be excessive rainfall due to slow storm motion and clustering. Later in the afternoon, storms may tend to merge into a large MCS which will move to the north / northeast.

All seems close again - but is it close enough??? There will be some frantic radar watching in Kent into the late evening I bet.

[Neilsouth]

Any chance of a detailed update for tonight/morning? thankyou

[Stuart]

And for Today

Storm Forecast Issued: 2010-07-11 23:21:00

Valid: 2010-07-12 00:00:00 - 2010-07-12 23:59:00

Regions Affected

(SE England, East Anglia and Northern Ireland are included in the WATCH)

Synopsis

Low pressure "Mae" moving northeastwards away from the United Kingdom, west of Scandinavia, and Low pressure "Norina" approaching the southwest of the country will dominate the weather on Monday.

There is a low risk of convective activity associated with a developing wave along the cold front as cyclogenesis occurs over the southeast of England and nearby continent during the early hours in association with the destabilisation of the warm and humid airmass present there. The risk of thunder/lightning decreases significantly by dawn, but pulses of heavy rain may give localised flooding given the dry, baked nature of the ground.

Attention then turns to Northern Ireland and Ireland where scattered showers are forecast to develop as the winds fall slack. There is a low risk of thunder and/or lightning, with cloud heights limiting this chance, thus any lightning is likely to be quite isolated.

http://www.ukasf.co....orecast/id-309/

[Coast]

Well along with that UKASF watch, ESTOFEX have a level 3 for the Benelux countries and looking at the radar, it's kicking off there and just over the Channel in Calais currently.

Yet this side of the Channel.......

[BrickFielder]

Quick heads up for Wednesday where models show some potential as a trough moves north.

Its too early to pick out much in the way of detail yet, but worth keeping an eye on.

[Nick F]

Yes, was looking at those lightning wizard significant tornado parameters earlier, and does look like some low-level shear develops as surface winds back SE'erly ahead of approaching negatively tilted trough/low swinging in from the SW against general SW'erly flow aloft. This increasing low-level shear combined with some decent CAPE into several 100s may bring potential for a tornado or two.

Strongest deep layer shear doesn't really overlap this potential with winds aloft fairly unidirectional from the SW, so storms may not have the best environment to organise into supercells to yield a severe threat, but a weak tornado or two and funnels cannot be ruled out at this stage, but still early days.