Cloud Base Information
Just wanted to clarify whether your cloud base information is above ground level or above mean sea level??
Windy changed it from cloud base to ceiling, but it is running under the same name on Windy. So the ceiling means > 50% of sky covered by clouds, in aviation it is higher than 4 octas, so it can be BKN = Broken or OVC = Overcast, where BKN = 5-7 octas, OVC = 8/8 octas fully covered.
And to answer your qestion, this parameter gives the height of ceiling in meters (m) or feet (ft) above the level of the model (ECMWF) orography, so it is AGL.
Read the corresponding article of Ceiling:
But be aware of it, because of the ECMWF model has a 9km resolution, so it's sampling the terrain with 9 km steps. If you are planning around mountainous areas, you can't rely on it, do not use it for planning in such areas.
You can also read this post:
@csabatatar Thanks mate, much appreciated!
@Gabou971 Thank you very much!