Here's something I've been meaning to post for a while. Last November 28th, after sunrise, I saw some Ac with some virga (cirrus). I guessed the hight of the cloud was getting on towards 15,000ft. When I went to collect my newspaper, I saw the Ac was dissolving fast and there was a mock sun, so I took a photo.
On the way back from the paper shop, about 10 minutes later, the Ac had gone and all that was left was the cirrus and halo.
I next checked the Chilbolton Lidar at http://www.chilbolton.rl.ac.uk/weather/default.htm
. This showed the Ac to have been at about 13,000ft and the cirrus seemed to have extended below that to near 7,000ft.
The following graph shows the temperature structure in the area near the time. The product is provided by the University of Wyoming Department of Atmospheris science. http://weather.uwyo.edu/upperair/sounding.html