Ruru Kraal, who took Correspondence School at Takaka, asks :-
Why do hurricanes blow anticlockwise in the Northern Hemisphere but clockwise in the Southern Hemisphere?
Bryan Lawrence, an atmospheric physicist at the University of Canterbury, responded.
The reason why large scale systems rotate in opposite directions comes down to the nature of our rotating planet.
Try two thought experiments. Imagine standing at the south pole and throwing a ball northward towards New Zealand. As the ball moves northward the planet will rotate beneath the moving ball (it might help to think that you had a rather strong arm, capable of throwing the ball some hundreds of kilometres). Because of the rotation, the ball will actually end up far to the west of where you aimed (or the direction of the initial force). The effect of the rotation in the southern hemisphere is to make things appear to move to the left of the direction in which they are forced. If you do the same thing from the north pole (except throwing southward) things still end up to the west of where you aimed, except this is now to the right of the direction of the initial force.
In a hurricane, the force is inward (towards the low pressure), but in the north things are deflected to the right (ie anticlockwise). In the south, the inward force results in a deflection to the left (and so the system rotates clockwise).