Haghir22. Where in UK are you (ref things brewing)
Cheerz
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So long as I make it home before anything falls from the sky. I've gotten used to not bringing my coat with me

That said - the convection really doesn't look that agressive. It's more overspil from that murk over northern France.

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Epsom.

A couple of hours later and still very oppressive. Nothing doing though.

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Chance of some isolated TS in the S & SE tomorrow if temps rise sufficiently to break the cap.

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Please explain:
If temperatures break the cap?
Cheers
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BBC forecasts talking of late afternoon thunderstorms in the SE in response to the heat and presumably topographic triggering as The Chilterns was mentioned. A quick look at soundings confirms reasonable instability from mid-levels to 30K+ feet based on both Herstmonceux and Cambridge(below)

http://rasp.inn.leedsmet.ac.uk/UK+0/FCST/sounding5.curr.1700lst.d2.png

I live a few miles away, and, while I was at work at the time, didn't see any sign of storm potential from that cloud which spilled in from France in the afternoon. Felt muggy though!

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Hi, thanks for that, you do get the odd anomaly from this lightning app, must be.doen to the hot weather, unless someone can explain otherwise (rogue lightning strikes from lightning detection systems)
Cheers
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I noticed that the BBC forecast last night showed a couple of storms in the south east corner, but the presenter made no mention of it. Anyone know what the chances are today? It's certainly the hottest start this morning of the spell so far. Yesterday felt close too. London was like a pressure cooker at around 5pm. I was glad to get back out to the greenery of Surrey.

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Likely to be a few very isolated thunderstorms so most will miss them. Pretty strong cape and negative lifted index according to the high resolution models.

It's more of the same with respect storm potential really. No major triggering but the soup is primed so to speak so a push from mainly topography will be required, as it has been for the last week.
The high-res ppn models more or less follow the BBC graphics this morning in developing the odd storm around the Herts/Berks area and maybe down into Surrey later.

My eye however is drawn to an uptick in chances of a decent plume for early next week - one to watch.

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Hi, can someone from the higher echelons of Two weather explain to us mere mortal weather watchers what "breaking the cap" means
Cheers
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The 'cap' is basically the inhibition on explosive convection that often exists due to a layer of modified, often slightly warmer air aloft. The parcels of rising air are prevented from continuing to an altitude where water vapour condenses out by this layer and hence convection is prohibited. Simply put it caps or puts a lid on convection.
When other factors countering this effect (parcel temperature, dynamic forcing, etc) exceed the inhibition, the cap breaks (ala 'breaking the cap').
The main disadvantage of the phenomen is the consumption of copious amounts of coffee and fast food waiting for the cap to break when chasing in the States. The additional weight gained takes ages to burn off LOL.

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The Cap is a layer of stable air aloft that prevents convection. It might be warm and humid at the surface, but this layer of stable air aloft prevents the warm and moist air from conectively rising above it to build into showers or thunderstorms. Typical of the situation we have now where High Pressure is dominant.

Think of it as a cap on a bottle of fizzy pop. You can shake it and get the liquid beneath pretty agitated, but as long as the cap is in place, it stays in the bottle.

This cap can be broken by heating or mechanical lift, but often the parameters are insufficient to break the cap under any circumstances. This is known as a being Stable. If the parameters are right, then given enough heating at the surface, or though convergence zones, orogrpahic lift, cooler air infilitrating aloft etc. then the Cap can be broken, which is known as Conditional Instability. Often the most violent thunderstorms occur with conditional instability, as all the energy accumulated beneath the cap is released at once when the cap is broken (the cap comes off the fizzy bottle).

 EDIT: Beat me to it Neil. What he said as well.

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It's an inversion layer of warm and dry air trapped in the mid-level thus preventing convection from taking place, but if there is a pocket of really warm and moist air rising from the surface, it may have the "oomph" to break through that inversion layer and feast on the cold air aloft (often associated with high-based type storms).

Or at least I think that is what it is.

EDIT: Whoops. Ben and Neil has beaten me to it as we all typed up our posts at the same time, but I do like the fizzy pop idea!

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Its there again!! 12:30 weds 17th July 2013
That rogue lightning strike over Biddenden again! Slightly different position, but defo Biddenden.....
Another anomaly I take it.....?

Thanks all ref explaining "breaking the cap"
Really informative from all who responded.... Particularly like the "pop bottle with cap" analogy! !! This stable layer, doez it vary in its composition/height/temperature? And how widespread can tbe cap be or small for that matter......?
Cheers
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Like any parameter, it varies greatly from place to place and time to time. Sometimes it breaks in a narrow corridor and it's all about getting yourself in the right position to be ready for it.

Incidentally, decent looking tops now breaking out about 20 miles to my North (mid-Hampshire up into Berkshire perhaps).
Wouldn't be surprised to see a couple of isolated storms developing from mid-afternoon.

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it is either anaprop or tiny showers are popping up in the se on latest NW Radar (1400)

 

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Plenty of large cumulus but not breaking the cap. However a cloud went up over Alton a while back and gave a few minutes of large raindrops. Didn't really wet the ground as it was so sporadic!

We've got a few raindrops falling here in Hook as well.

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storm brewing near Watford lots of thunder around with a current temp of 28.9c

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Just about to leave Watford for home... Can confirm lots of thundery rumbles... no lightning (that I've noticed) or rainfall yet....

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Thunder!

I warned my family and friends of isolated thunderstorms and they live in Harrow and Watford  Just a shame I'm not going to see any, as usual