Convective / Storm Risk Discussion - 21st June 2013 onwards

[Coast]

Please use this thread to discuss your general thoughts and post your data on the potential for upcoming convective events.

 

Specific threads for days of high chance and activity will be opened as the information becomes more probable, like this for tomorrow:

 

http://forum.netweather.tv/topic/77020-thunderstorm-potential-and-activity-for-wednesday-19th-june-2013/

Edited June 18, 2013 by Coast

[Nick F]

Netweather Storm Forecast for Today: http://www.netweather.tv/index.cgi?action=convective;sess=

 

NMM High-Res model showing CAPE building across SE England and E Anglia this afternoon and evening, probably in response to humid air and some sunshine breaking through, so potential for some home-grown storms developing here and also some storms imported from the near continent arriving overnight.

 

Also some scattered showers and isolated storms possible further north and west across England and Wales.

 

 

[NO LONGER POSTING]

http://www.sat24.com/?ir=true&co=true&li=false

 

 

Absolutely ridiculous amount of very heavy rain moving up from France.. The models don't want it to migrate any more North but I can't see it not moving into our shores..

[Coast]

Here's what ESTOFEX have for the cross-over period through today up until tomorrow morning:

 

 

SYNOPSIS

 

A plume of very steep lapse rates has been advected over western part of Europe between two major synoptic-scale features: a deep trough centered over Iberia and a large ridge over the Central Mediterranean and Central Europe. This is confirmed by most of the sounding measurements from the area. A wavy frontal boundary stretches around the warm sector with 850 hPa temperatures exceeding 20°C. Such pattern will remain mostly quasi-stationary during the forecast period without any major changes in the position of the main frontal zones. Surrounding the ridge a belt of strong flow is observed with windspeeds between 20 - 40 m/s at 500 hPa.

 

Steep mid-level lapse rates atop moist boundary layer are expected to contribute to the development of moderate to high CAPE values over a large area. However, strong capping and lack of strong "forcing" will likely prevent explosive or widespread growth of deep moist convection apart from a few locations and this makes the forecast quite challenging

 

... BENELUX, Northeastern France, Central and Northern Germany ...

 

A very isolated convection is possible along the warm front in the environment of very steep lapse rates and moderate to strong vertical wind shear. In such conditions, supercells are possible, capable of (very) large hail and severe wind gusts. Questionable, very uncertain initiation precludes higher level issuance attm.

 

 

 

[Coast]

UKASF:

 

Slight

 

Forecaster: Dan

Last Updated: 2013-06-18 00:32:00

Valid: 2013-06-18 00:00:00 - 2013-06-18 23:59:00

 

 

Synopsis:

 

Iberia trough becomes a cut-off low, with slight upper ridging over southern Britain. Moisture advection continues to nudge northwards through Tuesday, behind a surface warm front, although a tongue of drier/cooler air will advect across SW/CS England for a time, suppressing convection chances here by the afternoon.

Discussion:

 

As the front edge of a plume, characterised by high ThetaE/ThetaW, continues to advect northwards along the warm frontal boundary, further elevated convection is expected in almost any part of the SLGT area, with the potential for sporadic lightning and locally heavy rain. Activity will continue across the Midlands/Wales/East Anglia into southern portions of northern England by the afternoon, but with the lightning potential ever decreasing through the day as the frontal gradient weakens and instability reduces.

 

Some models simulate surface-based convection development over Kent/Sussex/Essex late in the afternoon and into the evening in an environment of high CAPE (locally near 1000 J/kg), provided surface temperatures (resultant from insolation) reach the projected 23-25C. It is thought given the slack synoptic flow, local seabreeze convergence coupled with upslope flow may allow a thunderstorm or two to form, although exact locations will be difficult to ascertain at this stage. 30-40kts DLS would allow any isolated thunderstorms to remain fairly well-organised, with perhaps some reasonably-sized hail given instability present. Such convection is not a certainty, but a possibility that needs monitoring through Tuesday.

 

Most models then simulate further elevated convection over the eastern English Channel and southern North Sea through the evening and overnight hours (beyond this forecast period), perhaps merging into an MCS-like feature by the end of the night and affecting Norfolk/Suffolk/Essex/Kent/East Sussex. More detail on this will be included in the forecast for Wednesday, assuming the potential remains by then. 

 

Edited June 18, 2013 by Coast

[stainesbloke]

http://www.sat24.com/?ir=true&co=true&li=false

Absolutely ridiculous amount of very heavy rain moving up from France.. The models don't want it to migrate any more North but I can't see it not moving into our shores..

Yes, that's a serious amount of rain, it's even affecting eastern Spain! Unusual. Looks like its heading straight for the UK, it will probably move NW once it's over the Channel but I'm not expecting much in the way of thundery activity here. Too cool and cloudy

[Coast]

Need I add any more to these pretty pictures????

 

 

 

 

 

A small corner of the SE with chances later, then we move on to tomorrow......

[Coast]

NMM similar:

 

 

 

 

 

 

 

 

 

 

[chionomaniac]

NMM similar

NMM suggests that a homegrown MCS forms over the south coast this evening and heads towards East Anglia by  early morning. Prior to that some home grown storms may also be set off further north during the afternoon. Tomorrow not looking as favourable now.

[stainesbloke]

I'm not surprised by the big downgrades in thunderstorm risk, we need heat to kick things off. Sadly the sunny skies that would give this heat are well and truly absent.

[Harry]

After lead like skies this morning, the Sun is starting to break through here in London. Hopefully will see some decent warming now.

[Coast]

Currently:

 

 

[Harry]

All in all its fairly tragic how non-eventful thinks are projected to be at this stage...first sense of pessimism I've had for a number of days in respect of this 'event'. 

 

Still, must crack on so to speak.

[Tom Jarvis]

Here in the heart of East Sussex there are clear blue skies with some wispy clouds. The sun is heating things up very nicely

[Norfolk Sheep]

NMM suggests that a homegrown MCS forms over the south coast this evening and heads towards East Anglia by  early morning. Prior to that some home grown storms may also be set off further north during the afternoon. Tomorrow not looking as favourable now.

Hmm, these overnight MCS usually mean a lot of cloud hanging around during the day, inhibiting any further developments.....

[Harry]

MCS please!!!!!! Bank!!!! 

[Team Jo]

Grey & Hoomid here already, Cape looking promising tomorrow, although not as high as forecast yesterday, shame I'll be in Cardiff where I think the risk is a bit of a swizz

[Nick F]

http://www.sat24.com/?ir=true&co=true&li=false

 

 

Absolutely ridiculous amount of very heavy rain moving up from France.. The models don't want it to migrate any more North but I can't see it not moving into our shores..

 

Yes, that's a serious amount of rain, it's even affecting eastern Spain! Unusual. Looks like its heading straight for the UK, it will probably move NW once it's over the Channel but I'm not expecting much in the way of thundery activity here. Too cool and cloudy

 

That be the cold front to our S over France, could bring an MCS later today.

 

[Harry]

That be the cold front to our S over France, could bring an MCS later today.

 

fx00_tu06z.gif

 

Fully appreciating the complexity of such a setup, how do you view the chances of that happening Nick?

Edited June 18, 2013 by Harry

[Coast]

Blimey that's a very busy system going on there:

 

[nanu]

so maybe an average chance today??  bbc says NO all day tomorrow, but wet n horrible and thundery for thursday  ,, so that may turn out to be a damp and drizzzly then knowing our shores!! The skys well tell..

[Harry]

so maybe an average chance today??  bbc says NO all day tomorrow, but wet n horrible and thundery for thursday  ,, so that may turn out to be a damp and drizzzly then knowing our shores!! The skys well tell..

 

No no no that's not good news at all...I'm off tomorrow afternoon and was hoping to grab some developments

 

Coast, all looking very frontal from that radar grab - I note the MCS' mixed in there, but am curious to see whether anything explosive develops over the continent which may come our way....eyes on the radars and satellite images

[VillagePlank]

NMM suggests that a homegrown MCS forms over the south coast this evening and heads towards East Anglia by  early morning. Prior to that some home grown storms may also be set off further north during the afternoon. Tomorrow not looking as favourable now.

 

NAE going for imports,

 

 

And then the SE corner has this to look forward to, tomorrow evening,

 

Edited June 18, 2013 by Sparkicle

[Nick F]

Fully appreciating the complexity of such a setup, how do you view the chances of that happening Nick?

 

Notoriously fickle these plume set-ups, looks like we could end up with some thundery rain arriving across the SE/central S England late morning and into the afternoon, gliding N/NW along the cold front - which could kill off any chance of home-grown development. Just have to hope the convective system coming north out of France peps up and gets more electrically active as the day progresses, as we are in the usual late morning minimum for lightning activity.

Edited June 18, 2013 by Nick F

[Darren Bown]

It's warm and sultry here, sun's been out all morning so far too. Getting lovely and warm.