I was experimenting with OpenCV today, and got this velocity field overlay video:There's very little, if any, parallax in the clouds. If there is some then you should be able to demonstrate it - and then demonstrate that it changes.
You seem to be applying some subjective metric. You need to be able to measure it - or at least point it out so other people can see it.
I think others have done similar things before, but I can't immediately find them. Unfortunately a lot of noise, and it's not good at tracking in WHT mode. But it's interesting, and might be worth more work.