Convective / Storm Risk Discussion - 14th June 2013 onwards

[Convective]

You get your turn in the Autumn and Winter months..

 

Only two flashes in total over the last three winters and autumns aren't as spectacular as they used to be  Now it's just the odd rumble or a 10 minute thunderstorm. Oh the days where you would get one going on for a good 4 hours when the winds would fall light and they wouldn't move on...

[chapmanslade]

I would urge caution in here rather than ever more frenetic ramping followed by the inevitable wrist slashing posts. Whilst there is good potential for next week the events of the day before can have a huge impact. For example it is clear there are going to be some significant MCS developments in France and Belgium in the next few days which generates a load of cloud overspill and clag the following day. This can impact significantly on any insolation and thus storm development the next day. Significant MCS events 'create their own weather' and influence what comes after them.

I'm not suggesting it will be a non-event but at the same time some will get nothing so for them it will be.

[nitro_deluxe]

I would urge caution in here rather than ever more frenetic ramping followed by the inevitable wrist slashing posts. Whilst there is good potential for next week the events of the day before can have a huge impact. For example it is clear there are going to be some significant MCS developments in France and Belgium in the next few days which generates a load of cloud overspill and clag the following day. This can impact significantly on any insolation and thus storm development the next day. Significant MCS events 'create their own weather' and influence what comes after them.I'm not suggesting it will be a non-event but at the same time some will get nothing so for them it will be.

Indeed, we've been here many a times before - the last TS outbreak in the South came a little unannounced, despite much speculation of colder SSTs, perhaps a slightly more potent set up this time around, has to be noted. Well said though. Edited June 16, 2013 by triple_x1

[chapmanslade]

Cold SST's only influence boundary layer based storms and not the elevated storms we saw a week ago.

[chapmanslade]

http://cdn.nwstatic.co.uk/fax/PPVG89.png

I'd be keeping an eye on that warm front on Monday

[A.J]

I would urge caution in here rather than ever more frenetic ramping followed by the inevitable wrist slashing posts. Whilst there is good potential for next week the events of the day before can have a huge impact. For example it is clear there are going to be some significant MCS developments in France and Belgium in the next few days which generates a load of cloud overspill and clag the following day. This can impact significantly on any insolation and thus storm development the next day. Significant MCS events 'create their own weather' and influence what comes after them.I'm not suggesting it will be a non-event but at the same time some will get nothing so for them it will be.

A good post. I would feel happier with LP 100 or so miles further west come tuesday/wednesday, as an MCS over the benelux countries would probably be the death knell for UK storm activity due to cirrus overspill inhibiting convection even under watery sunshine

[nitro_deluxe]

Or, it could of course blossom into something slightly more memorable..weather eh? who needs it  

[VillagePlank]

Of course, all the normal caveats apply. However, if you consider this skew-t,

 

 

If you look at the equilibrium level, in this case approx 200hPa, it is associated with a 45kn wind which effectively acts as an exhaust for all the high level deritus. For sure, it could be stronger ....

 

I would say that the primary risk, then, is the macroscale environment; ie will the plume actually reach the UK ... long way to go, and encouraging charts for thunderstorm lovers.

Edited June 16, 2013 by Sparkicle

[Eskimo]

How common is it for lifted indexes to reach -8/-10? And CAPE values at 2500J/kg?

Edited June 16, 2013 by PerfectStorm

[VillagePlank]

Pretty rare in the UK, I would think; I don't think in reality it will get that low and high respectively, because of that. It would be, perhaps, a once in 20 year event ??

[Ben Sainsbury]

And the charts go bang; the cape is all gone

[Stormyking]

Urmm I don't know whether to start getting excited for tomorrow night or wait for tomorrows updates first. I think waiting will be the best bet, but pleaseeee pleaseeee happen! 

[Chris K]

And the charts go bang; the cape is all gone

 

Hah yea as per usual, the GFS shows epic runs for a day or so then drops it to match a more believable outcome.

 

Still, there could be something decent along the S coast tomorrow night and the SE? Not sure how far North and West anything will get really. More runs needed but my IMBY pessimism is already playing out in this 12z.

Edited June 16, 2013 by Chris K

[Hathers]

Has the cape gone now for Wednesday? It was looking great this morning.

[Supacell]

On the latest run from the GFS, Wednesday's CAPE has all shifted east. Maybe a few weak thundery showers but nothing like what the earlier runs were showing - that is reserved for the Low Countries again. It is, however, just one run.

[Methuselah]

I think we need call the Caped Crusader!

[VillagePlank]

GFS is virtually the coolest member, here, for the 12z, for the period in question,

 

 

As always more runs, will GEFS start to fade, too, in line with GFS?

Edited June 16, 2013 by Sparkicle

[Cloud 10]

I think we need call the Caped Crusader!

 There's a super-hero for every occasion!

 

[MP-R]

Well originally I was going to say that the west would do particularly well out of such a synoptic situation as Wednesday, with winds from the east sending storms across from an eastern breeding ground, but alas, the situation has changed. It would appear winds will be more from the NE on Wednesday with most of the CAPE reserved for the eastern fringe and the Low Countries.

[nitro_deluxe]

Personally I'm all for a slight wobble in proceedings re convective potential - makes it all the more realistic and with plenty of time remaining for change..again. Until at least we're in a more reliable timeframe? which certainly isn't today...

In fact as we all know, in the UK anyhow - sometimes storms or their forecasts, can't always be classed as official or until they're pretty much upon us.

Edited June 16, 2013 by triple_x1

[Summer Sun]

Synopsis:

 

Trough disruption over the eastern North Atlantic will result with a sharpening upper trough over Iberia. The British Isles will set beneath a slight upper ridge, on the forward side of the upper trough. At the surface a warm front will straddle the English Channel/northern France for much of the forecast period. Behind the front, an airmass characterised by high ThetaE will slowly advect northwards through Monday.

 

Discussion:

 

Firstly, it is worth noting that this forecast period runs until midnight Monday night (ie 23z Monday). It is likely that thunderstorms will develop/continue beyond this forecast period over parts of the highlighted (and possibly other) areas.

... SE, CS & SW ENGLAND ...

As high ThetaE continues to advect northwards through the latter stages of Monday afternoon, and through the evening and overnight, isentropic upglide will allow scattered elevated showers and thunderstorms to develop over the English Channel and neighbouring coastal counties in an environment of significant MLCAPE. In addition, surface-based thunderstorms over northern France will become increasingly elevated above the PBL as they continue to drift slowly northwards through the evening hours. Best period of development appears to be from 18z through to the end of the forecast period.

30-40kts DLS (corrected for elevated potential) will allow elevated thunderstorms to become reasonably well-organised and last for some time. Due to the elevated nature of the convection, severe weather will be limited somewhat, but hail is possible in any stronger cores along with the risk of local flooding given PWAT values >30mm with slow-moving storms.

Even at this stage, two main uncertainties will affect this forecast, both of which NWP tend to struggle to resolve. The first is the nature of the Iberia trough disruption, and therefore how far north the zone of elevated convection reaches - the SLGT may need to be extended further north if conditions warrant nearer the time. The second uncertainty is how much mid-level convection will be generated. Given the amount of instability forecast, it would be preferable to upgrade *some areas* to a MDT, but at present the areas most likely to see more widespread convection (and hence coverage) remains uncertain. Therefore, we may upgrade to a MDT during Monday, depending on the forecast evolution.

 

http://ukasf.co.uk/storm-forecasts/251

Edited June 16, 2013 by Summer Sun

[dave48]

A couple of storms in central France with cloud tops up to -60 now, with strong sferic returns on atd.

 

Not destined for us, but good to see the atmosphere down there is conducive as the plume heads north.

[Supacell]

The forecast from ukasf makes interesting reading and i am starting to think that the south coast may get a light show later on tomorrow and into the night. Possibly Wednesdays promise is meaning the potential tomorrow is being overlooked.

[Methuselah]

The forecast from ukasf makes interesting reading and i am starting to think that the south coast may get a light show later on tomorrow and into the night. Possibly Wednesdays promise is meaning the potential tomorrow is being overlooked.

Should we issue a 'Light Shower Warning' SC? 

[nitro_deluxe]

You could always fiddle with the light switches whilst listening to thunder via youtube?

Nearest some of us get to a decent TS lol...really hope things fall into place, any storm drought is painful enough, middle to back end of June and on is into new territory for me!

Still a lot of water to pass under the proverbial until Wednesday not least tomorrows potential for a few.