I'm not usually very interested in sunset photos, but I randomly decided to view this thread, and saw this picture, and it gave me a strange sense of deja vu... looking back a few years, I found this one that I took of the Griffith Observatory (with an Olympus XZ-2)... interesting similarity.
Wonderful shots, I think they are https://en.wikipedia.org/wiki/Polar_stratospheric_cloud.
Might be but i am from india where the temperature drops to like 50 degree and remain average cold hardly around 12 degree in peak winters. So this phenomena I saw it for the first time post my 18 years of photography career and love for the clouds. although i have grabbed opportunity and have plenty of diff structures captured from what i post few here.Wonderful shots, I think they are https://en.wikipedia.org/wiki/Polar_stratospheric_cloud.
They were cranked up a bit in post but 80% natural i would say.Whoa, really otherwordly feel!
Are these the plain sight colors or they came up that intense after post processing/