With hundreds of storm-tracking stations trying to relay information as quickly as possible, scientists need a short, easy to understand naming convention for hurricanes.
Starting in 1950, hurricanes began getting names but for the first three years the same names repeated each year, which became confusing.
From 1953 until 1979, it was customary to use only female names, supposedly after girlfriends and wives of Army and Navy meteorologists.
The system we have today began in 1979, and runs alphabetically through male and female names starting with a name beginning with the letter A, such as Arlene.
Each year the names are different from the last until the six-year cycle restarts. In 2011, the following names have been allocated:
Arlene, Bret, Cindy, Don, Emily, Franklin, Gert, Harvey, Irene, Jose, Katia, Lee, Maria, Nate, Ophelia, Philippe, Rina, Sean, Tammy, Vince, Whitney
Next year the names will begin with Alberto, Beryl, Chris, and so on.
Like 74 other Atlantic hurricanes, Katrina's name has been permanently retired to reduce confusion and show respect for those who lost their lives in the hurricane. All hurricanes that result in extraordinary loss of life have their names retired, and are replaced by another name beginning with the same letter. The name Katrina was replaced with Katia, which will be the name assigned to the eleventh hurricane in the 2011 season.
Irene 2005 never came ashore and only reached Category 2. This year, Hurricane Irene is expected to reach Category 4 by the time it comes ashore.