4 Stages of Hurricane.
1. Tropical Wave - Wind speeds of less than 25 mph
2. Tropical Depression - Closed circulation, rotation, and sustained winds.
3. Tropical Strom - Thunderstorm activity moves over closed circulation and sustained winds reach up to 39 mph.
4. Hurricane - When closed circulation becomes an eye, sustained winds reach 74 mph or higher. At this stage, the hurricane can cause significant damage.
