That was due to turbulence, which is a different thing. Turbulence can be caused by air flowing over terrain below.
Here is a nice picture. This is not related to whether the airflow is a tailwind or a headwind
relative to the aircraft.
A lot of pilots think that a plane flies somehow "sideways" when there is a crosswind, for example. One pilot swore blindly his plane vibrated more if flying in a crosswind. It's a favourite old topic - always raises a little smile. I have even met an instructor who believed this.