torrential now

garage getting flooded again

roads outside turning to rivers

hammering down, town centre valley likely to have some flash flooding as usual. Seems to happen every summer now

Massive rain here this afternoon. Can't recall seeing my veg plot flooded before! Sensational weather during the last few days. Heat, tornado See https://www.mix96.co.uk/news/local/2591108/videos-tornado-hits-marsworth/) , thunderstorms and torrential rain. 

We had more rain at work [in Sittingbourne] than I've seen there in 10 years and the roads around the school flooded to a good 9 inches of depth in places. The A2 past the school was a complete mess when I left, with Google Maps showing the dreaded dark red with gaps... meaning people haven't moved for so long that Google assumes the road is devoid of traffic!

Plenty of thunder around as well.

Meanwhile at home (12 miles away) there's been around 18mm of rain today... a fair bit, but not exceptional.

We're not far from all those reporting copious amounts of rain. Since Friday morning we've had a couple of brief showers, only 0.9mm in total on the AWS rain gauge. A bit of distant lightning on Saturday evening but nothing otherwise.

Torrential rain here in Tonbridge at the moment.  We're right under the area of heaviest ppn shown on the rainfall radar, from which I estimate the rate to be around 70mm/hour.  (Sorry no measurement myself - I don't have a weather station.)

Angus

We just had our first rumble of thunder of this spell loud enough to be heard indoors. Only 0.6mm of rain so far today whereas a PWS just 7.5 miles away north of Bracknell has had over 20mm.

27.4mm from today's downpours. Occasional thunder too. 

Yes we've had very little, although looking at the radar some heavier showers have made it to Yateley in the past hour (I'm still in London, where it is dry again after a very wet day with lengthy thunderstorms)

We've had 0.9mm of rain this evening so that's more than doubled our total since last Friday! About three rumbles of thunder too.

Yes a line aimed at North Kent and a large clump heading towards Essex and Suffolk.

http://www.raintoday.co.uk/mobile

nothing more than a few spots here this eve, a very grey and overcast humid day 2mm from the rain early this morning

sky a strange tint of red odd flash in the distance approx 15 miles from coast now

some clusters are holding

http://www.lightningmaps.org/#x=;m=sat;r=0;t=3;s=0;o=0;b=;n=0;

https://www.metoffice.gov.uk/public/weather/will-it-rain-today/#?tab=map&map=Rainfall&zoom=5&lon=-4.00&lat=55.74&fcTime=1527580800

 with interest  from SC

http://www.estofex.org/

I'll try again in another thread.

What is the source of this unstable atmosphere? 

To what I'm getting at, for example, in a typical Atlantic low pressure in UK in summer, the Polar Maritime or Returning Polar Maritime from Greenland is the source of unstable air flowing over strongly heated land generating convection, but what about in this current synopsis? 

Thanks.

You are correct to some extent in terms of their genesis, but they are now rooting into lower layers and I suspect they will be rain machines as they move onwards rather than the big lightning producers that they were over Holland as they evolve.

You've answered your own question in what you've said.

Currently we have moisture being pumped north from the Med via the HP to the N/NE combined with low pressure over France/Spain. We often get this set-up in a transitory scenario where we have warm air adverted north before an LP system moves in from the west ("Three fine days and then a thunderstorm"). The difference here is that we have blocking also to the west and north with a cut-off low providing the heat pump, therefore we have sustained moisture, heat and instability for some areas, with no clear run for the Atlantic to smash through the block.

Your Atlantic LP PM scenario will give classic popcorn showers or storms, but is never conducive to high CAPE or long term instability due to the mobile nature of the Atlantic push.