The most violent activity takes place in this area called the eyewall . There, as the spiraling air rises and cools, moisture condenses into tiny droplets, forming clouds and rainbands. The result is a column of rapidly rising air. Note the clouds that form the eyewall in the upper part of the photo to the left. A tropical disturbance is a discrete system of clouds, showers, and thunderstorms that originates in the tropical convergence zone and maintains its identify for 24 hours or more.
Tropical waves are a type of tropical disturbance.
They are troughs of low pressure which move generally from east to west, imbedded in the tropical easterly winds. These waves move off of the west coast of Africa and travel westward passing below the United States as they go. Given favorable conditions, a tropical depression may grow in intensity. When the winds exceed 38 mph, the storm system is referred to as a tropical storm and is given a male or female name by the National Hurricane Center. The winds in some hurricanes become much stronger, though.