Was the high altitude turbulence encountered over the Pyrenees due to wind shear or high speed penetration of short period waves? I imagine waves that appear smooth to me at 50 kts, might seem quite different at 500 kts.
Classic "rotor" seems unlikely at the altitudes reported. Are there any meteorologists who can comment?
IANAM(eteorologist) but from the wind reports given earlier, it sounds like the strongest winds were in a lower layer near the mountain tops. When this happens and the temperature profile is suitable for wave, the waves get steeper with increasing height and may actually "break". This can generate some pretty nasty turbulence, especially if you're travelling fast.
I remember wave soaring behind the Brecon Beacons in a southerly wind. At ground level it was 180/25 but became virtually calm at 6-7,000', then about 350/5 above that. This produced a wall of cloud that became steeper and steeper until it actually started to overhang; you could see amazing ripples and vortices forming and decaying on the cloud edge, some with real violence. There was narrow lift up to 1,500 fpm which stopped abruptly at the shear level. I wouldn't have liked to fly an aircraft through there at that height...