Hurricanes are the most violent storms on Earth. People call these storms by other names, such as typhoons or cyclones, depending on where they occur.
The scientific term for all these storms is tropical cyclone. Only tropical cyclones that form over the Atlantic Ocean or eastern Pacific Ocean are called “hurricanes.” Whatever they are called, tropical cyclones all form the same way.
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 rises upward from near the surface.
Because this air moves up and away from the surface, there is less air left near the surface. Another way to say the same thing is that the warm air rises, causing an area of lower air pressure below.