Again, I am not an advocate for the video being authentic... the CGI out there today can be very, very convincing.
I am not a weather expert either... but looking at all of the real photos of this kind of phenomenon, I can't help but notice that none of the mirages are seen in clouds (the sky appears to be basically cloud free in the area of the mirage). Due to the physics of bending light, there may be a good reason for the absence of mirages in clouds... but this is only speculation on my part. The brief video I have seen just does not show enough evidence to fully understand what is going on (for example, where is the location of the sun relative to the camera). I am sure it is just a matter of time for the answer to be revealed (by folks who are smarter than me).
M