Storms get names when they build up winds of at least 39 miles per hour. That's tropical-storm status. The names come from lists kept by the World Meteorological Organization, in Geneva, Switzerland.

There are six alphabetical lists of names for Atlantic storms. The lists are used in rotation — one list each year. Each list has 21 English, French, and Spanish names. They don't include any that begin with q, u, x, y, or z because there aren't enough names starting with those letters.

What if there are more than 21 tropical storms in a season? If that happens, names switch to the 24 letters of the Greek alphabet: Alpha, Beta, Gamma, Delta, and so on, but that's a very rare occurrence.

When a hurricane causes major destruction, its name may be "retired." If that happens, another name takes the place of the retired name on the list. "Katrina" was one of five names retired from the list in 2005 .