Thanks for the cirrus cloud update! Wasn't aware till now they are all composed of ice crystals.

I do agree with your point that once we are aware of something we tend to see it more.

As I mentioned in my article I've been shooting timelapse films for many years and consequently spend a lot of time looking at the clouds. Even when I am not shooting I am observing. Looking for interesting formations. Consequently I am 100% that if I had seen this before I would not only remember, I would have photographed it.

One thought comes to mind which is altitude. I am living 300m above sea level and only since moving here have I seen them. Perhaps they are just more visible from up here?