Hurricane forms over warm oceans. When oceans are heated up by the sun, they warm up and exchange the heat with the atmosphere creating an area of low pressure. The local warm air, laden with moisture from the ocean, rises. Cool air from the surrounding high-pressure regions moves in from the surface to replace the rising warm air. As the warm air rises and cools, the moisture in it condenses. This dumps heat of condensation and warms up the upper atmosphere pushing the clouds even higher. This movement of air forms a column, The column spins due to the Coriolis effect of the earth and form an eye in the middle as the air masses of different densities spiral around each other.
Hurricanes form over the tropics because the oceans near the equatorial region are heated more from the sun - due to its position more or less overhead of the region most of the year.
