Oh dear. I think you've been caught out by the simplified explanation of Coriolis which works as you say, but isn't really an accurate explanation. Read the Wikipedia entry - Coriolis force appears because a body on the surface of the earth is being accelerated by gravity into the circular path that the earth's surface is following (without gravity it would fly off in a straight line into space - Newton's laws, inertia and all that) and when itmoves with respect to the rotating earth it appears to have an additional force acting on it - the Coriolis force.
Lattitude doesn't really come into it.
It really is a swine to understand without the maths...
H