a cyclone is an area of closed or system of winds that rotates about a center of low atmospheric pressure, advances at a speed of 20 to 30 miles (about 30 to 50 kilometers) an hour, and often brings heavy rain
Tropical cyclones begin as disturbances in the air over warm ocean waters. A tropical storm develops once the wind speed reaches 39 miles (63 kilometers) per hour. If winds blow faster than 74 miles (119 kilometers) per hour, the tropical storm becomes a cyclone.
From above, a tropical cyclone looks like a huge disk of clouds. The disk can be 200 miles (320 kilometers) across. Within the storm, high-speed winds move in a spiral around a calm center, called the eye. The eye is an area of low pressure and clear skies, surrounded by a wall of clouds. When the eye passes overhead, it seems as if the storm has ended. However, the opposite side of the storm brings back the strong winds and heavy rain.
Tropical cyclones can cause ocean waves to rise to 20 feet (6 meters) above their normal height. The large waves, called a storm surge, can flood coastal cities.
Tropical cyclones get their energy from warmth and moisture that rise from the ocean surface. When the storm passes over colder waters or a large land area, it loses its source of energy. The storm then dies.