Unusual sighting.

[Peter Drew]

Today at 6.55pm I looked up to identify a passing plane when I noticed, almost overhead, what appeared to be a striaght piece of a rainbow with strong prismatic colours about 2  degrees in length. I'm quite familiar with atmospheric phenomena and presume it was some form of nacreous cloud but I don't recall seeing such a display so far from the Sun and other nearby nacreous cloud candidates showed no sign of prismatic colour. The spectacle lasted for no more than 30 seconds from first sighting.

[Stu]

Must have been fascinating to see Peter, always something new to see.

[Planet X]

Sounds a little like a Circumzenithal arc maybe?

[Debo]

I agree with Planet X,  Circumzenithal arc sounds favorite.

Also known as a Bravais arc, here's one I photographed a while back.

[Peter Drew]

I think the photo of the Circumzenithal Arc nails it, thanks for posting it Debo.

[Dave In Vermont]

One of the dozen science-sites I subscribe to had an article the other day on a type of cloud I've never encountered - Kelvin-Helmhotz clouds. So I thought I'd drop by on by this fascinating thread and leave an image.

Daytime sky phenomena is a good antidote to cloudy nights!

Dave