These forms are therefore typically strongest when over or near water, and weaken quite rapidly over land.
Coastal damage may be caused by strong winds and rain, high waves (due to winds), storm surges (due to wind and severe pressure changes), and the potential of spawning tornadoes.
Weather in the eye is normally calm and free of clouds, although the sea may be extremely violent.
The cloudy outer edge of the eye is called the "eyewall".
Tropical cyclones are areas of relatively low pressure in the troposphere, with the largest pressure perturbations occurring at low altitudes near the surface.
On Earth, the pressures recorded at the centers of tropical cyclones are among the lowest ever observed at sea level.The opposite direction of circulation is due to the Coriolis effect.Tropical cyclones typically form over large bodies of relatively warm water.Tropical cyclones are typically between 100 and 2,000 km (62 and 1,243 mi) in diameter.The strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth's rotation as air flows inwards toward the axis of rotation.Coastal regions are particularly vulnerable to the impact of a tropical cyclone, compared to inland regions.The primary energy source for these storms is warm ocean waters.This radius is typically coincident with the inner radius of the eyewall, and has the strongest near-surface winds of the storm; consequently, it is known as the radius of maximum winds.The previously mentioned processes result in a nearly axisymmetric wind field: Wind speeds are low at the center, increase rapidly moving outwards to the radius of maximum winds, and then decay more gradually with radius to large radii.As air flows radially inward, it begins to rotate cyclonically (counter-clockwise in the Northern Hemisphere, and clockwise in the Southern Hemisphere) to conserve angular momentum.At an inner radius, air begins to ascend to the top of the troposphere.