The naming of tropical storms and hurricanes follows a precise, standardized procedure overseen by the World Meteorological Organization (WMO). This system simplifies communication for forecasters, emergency managers, and the public as a cyclone moves across an ocean basin. Although the English alphabet has 26 letters, the official lists for the Atlantic and Eastern Pacific basins intentionally exclude specific letters from the rotation. This selectivity is a deliberate choice to enhance clarity and safety in weather warnings.
The Specific Letters Excluded
The rotating lists for naming storms in the Atlantic Ocean and the Eastern North Pacific consistently omit five letters: Q, U, X, Y, and Z. Each annual list begins with “A” and concludes with “W,” resulting in 21 names per season. While other global storm basins have different naming conventions, the Atlantic and Eastern Pacific lists adhere to this 21-letter structure. This exclusion is a long-standing practice recognizing linguistic limitations within the regions covered by the naming system.
Rationale for Excluding Specific Letters
The primary reason for excluding Q, U, X, Y, and Z is practical and linguistic: the difficulty in finding a sufficient number of appropriate names. The WMO requires six names for each letter—one for each of the six rotating lists—that are brief, distinctive, and easily recognizable across all affected regions. For instance, the North Atlantic basin impacts areas where English, French, and Spanish are spoken, requiring names that translate and pronounce smoothly across these languages.
Names beginning with Q and U are particularly scarce in common usage across these linguistic groups, making it challenging to generate six distinct, internationally accepted options. X, Y, and Z present similar issues, having a limited pool of familiar names that satisfy the criteria for six separate lists. The goal is to ensure that a name like “Storm Zeta” or “Hurricane Quentin” is not confused or mispronounced during a high-stakes weather event, which could compromise safety warnings.
Structure of the Rotating Name Lists
The WMO maintains six distinct lists of names that are used in sequence and rotate on a six-year cycle. The list used for the current year will be used again six years later, assuming no names were retired. This structured rotation ensures the public can become familiar with the names while maintaining a fresh alphabetical sequence annually.
Each list proceeds alphabetically, starting with “A” for the first named storm, “B” for the second, and so on. A fundamental rule is the strict alternation between male and female names, a practice introduced in 1979. If a storm is particularly devastating or costly in terms of loss of life and damage, its name is permanently removed from the rotation. It is then replaced with a new name beginning with the same letter.
Handling Name Overflow
On rare occasions, a hurricane season is so hyperactive that all 21 names on the annual list are exhausted before the season ends. Historically, when the standard list ran out, the system switched to using the Greek alphabet, which occurred during the record-breaking seasons of 2005 and 2020. However, this practice was discontinued in 2021. The WMO found that Greek letters, such as “Eta” and “Iota,” created confusion and distracted from core hazard communication.
In lieu of the Greek alphabet, the WMO now maintains a separate, predetermined supplemental list of names. If the 21 names on the main list are used up, forecasters begin using names from this supplemental list in sequential order. This change ensures the naming process remains consistent and less confusing for the public, even during seasons that produce a high number of named storms.