Peter, from my gliding experience, there is never turbulence close under this cloud / it would not otherwise have such smooth edges. If the air is very humid, very small “wave oscilation” is actually required for this cloud to be formed – and there will be very little or perhaps even no rotor turbulence as a result. However, there MUST be some climbing air in its windward side (and descending air in the downind side) for this cloud to be formed through adiabatic cooling. It is not the climbing/descending air, that creates the dangerous turbulence. It is the rotor, which is created in the “triangle” between the climbing and descending air and the “flat” air underneath it.
If the humidity is high and wind speed low, lenticularis may be formed, but there may be very little rotor activity. Altitude also affects how severe turbulence you get. The closer to the lenticularis cloud (or above it) the safer you are.
aart wrote:
is that not a nasty lenticular rotor cloud which gives you lots of turbulence
As was said, lenticulars mark a wave (rotor can be marked by a cumulus [fractus]). There shouldn’t be a rotor this high up, it will be much closer to the ground (roughly under the ridge line). Waves are typically very smooth (if you’re in the right part of the wave). What you can encounter up high is what’s called a breaking wave (basically an unstable wave breaking up). Those buggers can be violent enough to tear off an engine or tail of an airliner (there have been such cases attributed to them IIRC). They are not always present, I would say such encounters are rare, but I don’t think you would soon forget one. And it must be “interesting” to fly into a 8k fpm downdraft (you shouldn’t get that this low). 
1500 fpm suggest it was a strong one.
I think my point was that one can get clouds like that forming without any significant wind.
I have certainly found ones like that.
No way would I go anywhere near them if say crossing the Alps and the TAS is 150kt while the GS is 200kt or 100kt 
