Thunderstorms, warm ocean water and light wind are needed for a hurricane to form (A). Once formed, a hurricane consists of huge rotating rain bands with a center of clear skies called the eye which is surrounded by the fast winds of the eyewall (B).
Tropical Storm: Wind speeds between 35 and 64 knots (40-73 mph)
Hurricane: Wind speed greater than 64 knots (74 mph)
Tropical Depression: Wind speeds between 20 and 34 knots (23-39 mph)
Tropical Disturbance: Thunderstorms with light cyclonic circulation
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