Satellite image of Hurricane Joaquin in 2015. (NASA)

The World Meteorological Organization retired two names from the list of Atlantic tropical cyclones Monday: Erika and Joaquin. This means they will no longer be used to name hurricanes.

Erika was first introduced in 1991 (replacing Elena 1985), and Joaquin was introduced in 2009 (replacing Juan 2003). Both of these cyclones were deadly or destructive enough in 2015 to warrant their permanent retirement. In the 2021 list, the E and J names will be Elsa and Julian.

Tracks of Erika and Joaquin during the 2015 Atlantic hurricane season. Colors indicate intensity. (B. McNoldy)

In the Atlantic naming method in use since 1979, six lists of names are recycled every six years. Within a given hurricane season, male and female names alternate, then the following year, the gender ordering is staggered (for example, Ana and Bill one year, Alex and Bonnie the next, etc).

Unless a name is retired, the exact same list of names is used again six years later. “If a tropical cyclone acquires special notoriety because of its strength, deaths, damage or other special reasons,” the WMO may determine that a name shall be retired from future use.

From 1953 to 1978, alphabetical lists featuring only female names were used but were not repeated in any regular fashion. From 1950 to 1952, storms were given names from the military phonetic alphabet, and they were not named at all before 1950. The first time a storm name was officially retired was in 1954.

Tracks of 80 storms whose names have been retired (1954-2014). The two storms from 2015 are not shown on here.

Since 1954, 82 names have been retired out of a total of 694 named storms. But as we like to say, there’s more to the story than the category.

A tropical cyclone can be especially deadly or destructive for multiple reasons, including storm surge, inland flooding caused by rainfall, and of course intense winds. A storm’s “category” is based solely on its peak wind speed, which is historically responsible for just 8 percent of tropical-cyclone-related fatalities in the United States. (1963 to 2012).

Cause of death in the United States directly attributable to Atlantic tropical cyclones, 1963–2012. (Rappaport, 2014)
Cause of death in the United States directly attributable to Atlantic tropical cyclones, 1963 to 2012. (Rappaport, 2014)

A name could be retired even if the storm was not intense as measured by its peak wind speed. If it produced devastating flash floods caused by heavy rain, the name also could be retired. If I break down the list of 82 retired names by the storm’s peak intensity (not necessarily its intensity at landfall), we see that the majority were major hurricanes at one point, but some were only tropical storms or Category 1 hurricanes. Erika 2015 joins Allison 2001 as the only tropical storms ever to be retired.

Number of retired names grouped by the storm’s peak intensity. (B. McNoldy)

We also can look at retirement by month of impact. Not surprisingly, the most destructive storms occur in September, flanked nearly evenly by August and October, while the remainder of the hurricane season has historically produced relatively few storms worthy of retirement.

Number of retired names grouped by the month during which the storm had its greatest impact. (B. McNoldy)

Finally, we can break down the list by letter. As one would expect, there have been many toward the beginning of the alphabet because they occur the most often. But there is a large peak at the letter I.  The I storm is the season’s ninth named storm, which climatologically forms on Oct. 7 — but the 10 “I” storms that were retired had a median formation date of Sept. 9, right at the peak of the season. These frequently retired letters are where the WMO Hurricane Committee tasked with creating the lists of names must get creative!

Number of retired names by the first letter of its name. (B. McNoldy)

We are now just over a month away from the beginning of the 2016 Atlantic hurricane season, and the first names on the list are Alex, Bonnie and Colin. New names on this list include Ian and Tobias, which replace Igor and Tomas from 2010.

* The list of retired names used here is from a composite of sources including NHC, HRD and WMO. Any discrepancies among the lists are minor and exist only in the 1950s and 1960s.