A northern hemisphere thing.
Weather systems, tornados and water down plugholes all rotate anti-clockwise up here - as does the earth itself (if viewed from a point directly above the north pole).
Or to put it another way:
Conservation of gravitational energy. The force of gravity causes force towards the center of the earth and the "curl conservation force" points away from the center
0=dV/dt + cDelxV + R' cDel.V, the curl DelxV is the counter force circulating anti-clockwise in the northern hemisphere. R' is the radial unit vector.
Roe have obviously studied this!
(or are susceptible to it's effect). See also Coriolis Effect.