Ruru Kraal, who takes Correspondence school at Takaka, asks :-
Do hurricanes change direction when they cross the equator?
Bryan Lawrence, an atmospheric physicist at the University of Canterbury, responded.
It turns out that hurricanes dont cross the equator, so they never change direction. The reason is rather complex to explain, but it has to do with the conservation of a quantity called angular momentum which essentially comes down to a measure of spin.
You've probably seen that when watching ice dancing: when the skater pulls their hands in above their head, they start to spin faster. To think about what would happen for a hurricane trying to cross from the north to the south, imagine for a moment that if you stood in the northern hemisphere, your head would point toward the north pole, and in the southern hemisphere, your head would point toward the south pole. (Not true, but close enough for this argument). Now think of the hurricane spinning clockwise like a dancer with her head pointing north. As it (or the dancer) comes across the equator, it would be like the dancer having to instantly jump upside down and stand on her head to conserve the sense of the spin.
For the hurricane this is very unlikely as the air up high would have to swap with the air below, instantaneously. Nature doesn't do things that aren't very likely very often.