How Does a Storm Become a Hurricane?
A hurricane starts out as a tropical disturbance. This is an area over warm ocean waters where rain clouds are building. A tropical disturbance sometimes grows into a tropical depression. This is an area of rotating thunderstorms with winds of 62 km/hr (38 mph) or less. A tropical depression becomes a tropical storm if its winds reach 63 km/hr (39 mph). A tropical storm becomes a hurricane if its winds reach 119 km/hr (74 mph).
