Cause of a Huricane

A hurricane begins as a Tropical Disturbance. A Tropical Disturbance has only a small circulation. As a Tropical Disturbance strengthens, pressure drops and winds increase to 20 knotical miles per hour, it becomes known as a Tropical Depression. The next stage in a hurricane's development is a Tropical Storm. A Tropical Depression becomes a Tropical Storm when winds increase to 35 knotical miles per hour. A Tropical Storm's circulation of clouds resembles a hurricane. The last stage in a Hurricane's development comes when the Tropical Storm's surface pressure continues to drop and wind speeds increase to 64 knotical miles per hour. The Tropical Storm develops into a full blown hurricane. Spiral rain bands rotate around the center, or "eye," of the hurricane.