Tropical cyclones, known as hurricanes in the Atlantic basin, are powerful weather systems characterized by a low-pressure center and organized thunderstorms that rotate around that center. These storms are assigned names once they reach tropical storm strength, defined by sustained wind speeds of 39 miles per hour or greater. The practice of naming these systems began to simplify communication between weather forecasters and the general public. Using short, distinctive names helps prevent confusion when multiple storms are active at the same time.
The Annual Alphabetical Naming Sequence
Hurricane names are assigned in a sequential alphabetical order each season from a pre-determined list established by the World Meteorological Organization’s (WMO) Hurricane Committee for the North Atlantic. The first named storm begins with ‘A’, the second with ‘B’, and so on, progressing through the alphabet. The lists incorporate gender alternation, where male and female names are used sequentially throughout. The Atlantic list contains 21 names, and the assignment occurs immediately when a tropical depression strengthens into a tropical storm. This naming sequence resets entirely at the beginning of every hurricane season.
The Six-Year Rotation and Name Retirement
The names used for Atlantic tropical cyclones are drawn from a set of six rotating lists. This means the list of names used in any given year will be recycled and used again six years later. A name is permanently removed from the rotation only if the storm was exceptionally destructive or deadly. The World Meteorological Organization retires these names out of sensitivity to the victims and to avoid confusion when referencing historical events. Following a storm’s retirement, the WMO committee selects a replacement name that begins with the same letter and maintains the same gender as the retired name.
Handling Skipped Letters and Supplemental Names
The main annual list of names does not include a name for every letter of the alphabet. Specifically, the letters Q, U, X, Y, and Z are skipped entirely in the Atlantic basin list. These letters are omitted because there are not enough common or easily recognizable first names that start with them, which could cause difficulties in communicating storm information across different languages and regions.
When a particularly active season exhausts the standard 21-name list, a supplemental list is now used. Before 2021, the Greek alphabet was used to name any additional storms beyond the 21st, which happened during the 2005 and 2020 seasons. The WMO decided to discontinue the Greek alphabet system because it caused confusion and distracted from hazard communication. The new supplemental list is a pre-determined, independent list of names that also follows an alphabetical order and is used sequentially after the initial 21 names have been exhausted.