I made the animation to better understanding.

The content which is almost static is not real. I was check it against original data from CHMI.

I think this bug is "new" - never ever i see somethink like this.
I dont know the architecture of your algorithms which prepair image data for animation but there is somethink wrong now,

I think it is the bug in combining the image data in time.
If you combine images w1 to w8 to animation it will be easy to view.
If you have the ability like "wayback machine" you shold view situation near Brno, Czech Republice half or one hour before this post.