Stormy Weather II

[oddoneout]

So who's nicked all our rain?! During the afternoon/evening yesterday the forecast gradually downplayed from several hours of heavy rain at 80% certainty to possibly 3 hours of light rain at 40 or 50%, in both cases overnight. So what did we get(here at least) - a sprinkle. Very welcome for laying the dust and freshening the air, but negligible in terms of quantity.
To add insult to injury there are still yellow banner warnings for rain and, because the Met Office summary is now East of England instead of East Anglia as it used to be, it is forecasting slow moving heavy showers.

[eighthobstruction]

....same here ooo....promised but not forthcoming...which led to me getting hose out (while having an attack of Labyrinthitus)

[Serial_Apologist]

A truly amazing thunderstorm hit us here in S London around 2 am, with a 15-minute downpour of waterfall intensity, so loud as to eclipse the sound of thunder and reduce visibility to a hundred metres. The vivid lightning then continued for another half hour, with several bolts landing close by - expecting a number of trees to have been hit. Luckily our outside drainage system coped folowing the big unblocking session back in the spring, and even the clothes drying compound had not become the usual swimming pool when I put the laundry on the line earlier. This was all "elevated" stuff, so the discharges needed to be powerful to reach the ground. Right now surface cumulus clouds are building up ominously, unsurprisingly given we are right in the centre of the cut-off low that's been hanging around mostly off the SW approaches for the past few days, so my washing is certainly in for few more rinses before this all clears up this evening, hopefully - I need a good night's sleep tonight! Surface winds have dropped right out making for difficulty in determining which way the weather is to be coming from. Currently most of the electrical activity is down Teamsaint's way.

[Petrushka]

Fairly constant light rain throughout the morning here in Staffordshire but it's not cold and - a big bonus this in my book - absolutely zero wind. The forecast temperature high for today is 19°C so we have a typical September mix of summer and autumn as one moves into the other.

[Nick Armstrong]

A truly amazing thunderstorm hit us here in S London around 2 am, with a 15-minute downpour of waterfall intensity, so loud as to eclipse the sound of thunder and reduce visibility to a hundred metres.

Yes, it was a biggie!

[Old Grumpy]

Yes, it was a biggie!

Impressive colours on the Met Office rain/cloud cover maps...

[vinteuil]

A truly amazing thunderstorm hit us here in S London around 2 am, with a 15-minute downpour of waterfall intensity, so loud as to eclipse the sound of thunder and reduce visibility to a hundred metres. The vivid lightning then continued for another half hour, with several bolts landing close by ...

... the thunder last night was of a kind I had never heard before, anywhere. Loud, but more particularly - very long in duration : not just flashes of lightning followed by a crash, but followed by loud rumbles that went on and on and on and on. I thought London was under bombardment : it was a relief when the rain came as I could then believe it was just a storm and not the outbreak of war...
.

[oddoneout]

Here we had an impressive posing of black clouds about 4-30pm that delivered - a failed attempt at drizzle for about 20 minutes. As the sun caught the droplets a splendid rainbow developed showing up nicely against the dark sky, then another appeared some way above it and a short while later as the higher secondary one faded an extra layer appeared inside the original one. All very decorative and certainly appropriate for a Sunday and the biblical interpretation of the rainbow(which must test faith for those flooded out around the world), but in the meantime the garden is shrivelling, the veg have given up and I can't get weeds out of the rock hard soil...
Question: why did the higher rainbow have the colours in the reverse order to the first rainbow but the third one to appear had the same order as the one it was tucked up against?

[Serial_Apologist]

... the thunder last night was of a kind I had never heard before, anywhere. Loud, but more particularly - very long in duration : not just flashes of lightning followed by a crash, but followed by loud rumbles that went on and on and on and on. I thought London was under bombardment : it was a relief when the rain came as I could then believe it was just a storm and not the outbreak of war...
.

From footage of last night I've seen, some of the lightning strikes were a combination of cloud-to-cloud and cloud-to-ground types. Inter cloud discharges produce the long type rolls as the shock wave reverberates along the length of the discharge, whereas cloud-to-ground strikes tend to produce the short, sharp, more explosive thunder claps. I rather wish I'd stayed by the window observing for the whole duration of the storm.

[Serial_Apologist]

This rather wonderful shot demonstrates my above point rather well. The left hand of the two strikes has travelled some way from the left before branching down to hit lightning conductors on the two tower blocks, while the one to the right is inter-cloud or intra-cloud. Assuming the flashes were simultaneous the thunder would manfest both characteristics, a loud retort at the point the lightning earthed and the longer more reverberative rumble. This is a remarlable photo by the way, since at the instant the strike takes place the whole sky would be a dazzling white, therefore the shot must have caught the discharge a split second later.

http://www.bbc.co.uk/weatherwatchers/report/b417993a-ea02-49ec-8345-0c7e284b22ff/

A link to another capture mentions that the strike resulted in a temporary power outage to the entire building.

[Old Grumpy]

http://www.bbc.co.uk/weatherwatchers/report/b417993a-ea02-49ec-8345-0c7e284b22ff/

Yes, S_A, that picture is definitely worth Page 3 of the Currant Bun...


...it's a stunna!

[Belgrove]

...
Question: why did the higher rainbow have the colours in the reverse order to the first rainbow but the third one to appear had the same order as the one it was tucked up against?

The first rainbow is caused by refraction of a light ray through water droplets, which collectively act like a prism. The secondary rainbow is caused by an internal reflection of the light within the droplet, which reverses the colours (a matter of geometry). A third reflection restores the colour sequence but the bow occurs at a distinct location, displaced towards the sun, from the primary and secondary bows. Insofar as the bow you saw was superimposed upon the primary, it indicates that this was a ‘supernumerary’ rainbow, which is a diffraction effect. Its origin comes from the wave nature of light rather than the refraction of rays, and it can generate colours distinct from the refractive rainbows. It is a very rare phenomenon so you were fortunate to observe it. Thanks for bringing it to our attention.

[gurnemanz]

Just returned from visiting friends in Lund, Sweden, where we had high 20s C temps and cloudless skies for a week. While there, we noted reports of storm and deluge in UK, thinking this would help the garden in our absence. As we returned yesterday coming over the Øresund Bridge to Copenhagen Airport the weather was just changing back to something more normal for September in that neck of the woods - i.e. a bit like the current weather here in N Wilts. 15C cloudy with some sun.

[oddoneout]

The first rainbow is caused by refraction of a light ray through water droplets, which collectively act like a prism. The secondary rainbow is caused by an internal reflection of the light within the droplet, which reverses the colours (a matter of geometry). A third reflection restores the colour sequence but the bow occurs at a distinct location, displaced towards the sun, from the primary and secondary bows. Insofar as the bow you saw was superimposed upon the primary, it indicates that this was a ‘supernumerary’ rainbow, which is a diffraction effect. Its origin comes from the wave nature of light rather than the refraction of rays, and it can generate colours distinct from the refractive rainbows. It is a very rare phenomenon so you were fortunate to observe it. Thanks for bringing it to our attention.

Thank you for the explanation. Having a name for the one I didn't recognise is helpful(especially if I remember it!). The 2 "ordinary" rainbows were striking( flat countryside means a lot of sky to make a backdrop, so rainbows are often, as in this case, large complete arcs) which was why I spent some time looking at them, and so was lucky enough to see, briefly, all 3 forms in place at the same time. Having looked up supernumerary* rainbows I'm glad I didn't go and get my camera - I would have missed most of it, and not got a good picture anyway.

* Or supernumeracy as one website has it

https://atoptics.co.uk/blog/supernumeracy-rainbows/

[Serial_Apologist]

Much much cooler today than yesterday, necessitating a jacket for my afternoon cycle to local shops. Actually cooler than forecast, with grey unbroken stratocumulus rolls blocking any chance of the 19C Met forecast. This appears to herald quite old conditions over the next 4 days, with temperatures only predicted to return to 19C at the weekend - a sure sign of an early autumn onset. So, unless warmth returns in October, a rarity even in these days, we have to be satisfied with just the two months of summer this year when temperatures exceeded 22C.

https://atoptics.co.uk/blog/supernumeracy-rainbows/

I'd always assumed sumernumerary rainbows to be hubs from where Lottery winnings were dispensed!