UKC Forums - meteorology question

meteorology question - wierd sunset rays

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pebbles 02 Sep 2016

fabulous sunset at almscliff last night. amongst other things I saw a really odd thing: dark rays (ie shadows of denser areas of cloud) emanating from a point OPPOSITE the sun, from the direction of harrogate. now i'm used to dark rays radiating from clouds when the sun is behind them - but what on earth can cause this when the sun is not behind the clouds, but opposite? any meteorologists here who can explain it? couldnt take a pic as I was belaying at the time.

lummox 02 Sep 2016

In reply to pebbles:

I think it was the shadow of a big cumulus tower cast on to alto cumulus. Gorgeous wasn't it ? Some friends got great pics and put them on FB.

Lemony 02 Sep 2016

In reply to pebbles:

Guessing it's the same think as gave the spectacular views at Headingley last night:
https://pbs.twimg.com/media/CrSp_vjWYAElbUk.jpg

Jon Read 02 Sep 2016

In reply to pebbles:

Anti-crepuscular rays.
Shadows cast by objects closer to the sun than you -- the near parallel shadows appear to converge.

Mark Bull 02 Sep 2016

In reply to pebbles:

The Atmospheric Optics site is a great resource for all such phenomena: http://www.atoptics.co.uk/atoptics/anti1.htm

OP pebbles 02 Sep 2016

In reply to lummox:
I saw the cumulus tower shadow - I got pics of that. but this was a different thing, a bit earlier on - multiple radiating dark rays emanating from the low in the EASTERN sky, opposite to the setting sun. wasnt closer to the sun than me - sun was in the west, dark rays were from the east, lowish towards the eastern horizon. wish I'd got pics of that too. I was trying to figure out how it could be cause but failed - wonder if some sort of reflection off ice crystals high up behind the eastern clouds was involved

Post edited at 12:14

Rigid Raider 02 Sep 2016

In reply to pebbles:

Your explanation is in the link above.

OP pebbles 02 Sep 2016

In reply to Mark Bull:

got it !!!! anticrepuscular or antisolar rays "Crepuscular rays appear to converge on the sun, anticrepuscular or antisolar rays converge in the opposite direction and you must have your back to the sun or sunset point to see them. They appear to converge towards the antisolar point, the point on the sky sphere directly opposite the sun. Like crepuscular rays they are parallel shafts of sunlight from holes in the clouds and their apparently odd directions are a perspective effect. Think of a long straight road, it converges towards the horizon but turn around and it also converges to the opposite horizon. Crepuscular and anticrepuscular rays behave in the same way.

Anticrepuscular rays are not rare but they must be sought carefully. When ordinary crepuscular rays are visible, turn around and search for their opposite numbers. More rarely, sunrays pass right across the sky." fabulous. thank you.