How do hurricanes form?

Tropical cyclones are like giant engines that use warm, moist air as fuel. That is why they form only over warm ocean waters near the equator. The warm, moist air over the ocean upsurges upward from near the surface. Because this air travels up and away from the surface, there is fewer air left near the surface. Another way to say the similar thing is that the warm air rises, causing an area of lower air pressure below.

A cumulonimbus cloud. A tropical cyclone has many of these, they form huge, circular bands. 

Air from surrounding atmosphere with greater air pressure pushes in to the low pressure zone. Then that "new" air becomes warm, humid and rises, too. As the warm air remains to rise, the surrounding air swirls in to take its place. As the warmed, moist air rises and cools off, the water in the air produce clouds. The entire system of clouds, wind spins and grows, fed by the ocean's heat and water vaporizing from the surface.

Storms that form north of the equator turn counter clockwise. Storms south of the equator spin clockwise. This variance is because of Earth's turning on its axis.

As the storm system rotates faster and faster, an eye forms in the center. It is very calm and clear in the eye, with very low air density. Higher pressure air from above flows down into the eye.

This is the diagram of the process on how hurricane occur

Video :

http://www.youtube.com/watch?feature=player_embedded&v=4f45jA5UxB0#!