Cloud Cover

[wxnut]

Hi - This is pretty picky, but I was curious to know what the criteria was for the gray concentric circles indicating the cloud cover on the airgrams and meteograms and what it is specifically referencing. Is it a measure of opacity of the clouds? Is it a percent chance of cloudiness at that location and time etc...? Any help would be greatly appreciated. Thanks

[TheRadarGuy]

@wxnut The clouds on the meteograms and airgrams show forecasted cloud height and thickness for a given time.

Height and thickness is verticle, and time is horizontal on the graphs.