from:
https://spaceplace.nasa.gov/hurricanes/en/
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.

A cumulonimbus cloud. A tropical cyclone has so many of these, they form huge, circular bands.
Air from surrounding areas with higher air pressure pushes in to the low pressure area. Then---snipt--