We start with a tropical depression, a low-pressure area in the center of a group of thunderstorms. From a satellite, it doesn’t look very organized, but it does have some rotation. Depressions are numbered by the National Hurricane Center. For example, TD8 was the eighth tropical depression to form this season.
Once the depression sustains wind over 39 MPH, we call it a tropical storm. At this stage we are already seeing problematic weather, usually heavy rains. If this storm develops strong rotation, and the wind speeds exceed 74 MPH, we have a hurricane. These are much easier to recognize because of their distinctive shape and the dark eye in the center. Hurricanes are rated 1 to 5, based on intensity. They can last for weeks, but they tend to lose power once they hit land.
Instead of numbers, hurricanes get names, which are selected from a pre-determined list that gets recycled every six years.