Lenticular clouds and stationary waves again

 I spotted this lenticular cloud hiding the Sun when we were coming back down the Sticks Pass to Thirlmere. Lenticular clouds are supposed to be formed when wind blows over mountains and the disturbance sets up stationary waves in the air. The water vapour gets trapped between the bottom and the top of the wave shape, forming a lens shaped cloud. What occurred to me today was that if it is a stationary wave, the cloud should stay in the same place. I took the picture below 15 minutes later.

 Lower level clouds have moved in from the north on the wind (from the right in the picture) but the lenticular cloud has stayed in roughly the same place. I was using the position of the Sun to show that the cloud was in the same place but realised that the Sun moves. When I did the sundial research last month I found that the Sun moves 15 degrees in one hour. It will move almost 4 degrees in 15 minutes. That is 4 little fingers.

 Thumb to little finger turns out to be 25 degrees.

I kept watching. The lenticular cloud did stay in the same place as lower cloud came in and obscured it. An hour later the sky cleared again and there were still the remnants of the lenticular cloud in the same place. Stationary waves, then.