Animation of the internal structure of a hurricane. The animation begins with the orbits of Earth Observation satellites, before zooming in on a hurricane in the western Atlantic ocean. This fades to show the precipitation level, mapped as colour_coded bulges of cloud, from grey lightest precipitation to blue heaviest. Precipitation occurs in cloud bands around a central clear eye. The heaviest rain and the fastest winds occur on the northern side of a westward_moving storm, under what is known as a 磆ot tower? a huge thunderstorm that rises above the tropopause. The hot tower is formed by warm, moist air grey arrows being drawn up from the surface, releasing latent heat red arrows as the water condenses, and ejecting cool, dry air grey into the upper troposphere. The Earth磗 rotation imparts spin to the system, an effect called the Coriolis effect. Successive warm updrafts cause a band of thunderstorms to develop around the rotating system. The cool air blue ring at the top of the troposphere descends due to its higher density, leaving a central region free of clouds, known as the eye. The eye is usually calm, while the strongest winds are found in the eyewall.