Subtropical Storm Wanda formed in the Atlantic over the weekend, striking the last name off the National Hurricane Center’s list for 2021. It is only the third time on record all of the Atlantic names have been used up, joining 2005, the season during which Katrina formed, and last year’s bombardment of 30 named storms.

Not until this year and last have the Atlantic storm names lists been exhausted in back-to-back years.

After a feverish stretch of storminess in August and September, Wanda was a long time coming. Since Hurricane Sam lost its tropical characteristics on Oct. 5, not a single storm occupied the Atlantic until Wanda was named at 11 p.m. Saturday.

October was not only a quiet month in the tropical Atlantic, but also across the world. Not a single storm of major hurricane strength spun up globally for the first time since 1977 during the month.

November is the final month of Atlantic hurricane season and, on average, one new storm is named. If that happens this year, the Hurricane Center will draw from a supplemental list of storm names for the first time, rather than using Greek letters as in the past.

Subtropical Storm Wanda

On Monday morning, Subtropical Storm Wanda was a 45 mph storm located just under 1,000 miles west of the Azores. It was moving southeast at 7 mph, its motion irregular and varied. It was embedded within a dip in the jet stream that was imparting more wind shear, or a change of wind speed and/or direction with height, on the system. Wind shear is disruptive to tropical cyclones and can inhibit further strengthening.

The Hurricane Center projects Wanda to maintain its current strength for the next few days as it turns east, before curving north well to the northwest of the Azores, sparing the Portuguese archipelago any direct impacts but generating some choppy surf. The storm is never expected to directly impact any land area.

Wanda is a subtropical storm because it exhibits both tropical and extratropical, or mid-latitude, characteristics. It initially contained subtle variations in temperature left over from fronts, but those have since dissipated. The storm is ingesting somewhat dry air as it swirls over cool sea surface temperatures, precluding further development, but a transition to a fully tropical structure is expected on Tuesday.

The storm will probably dissipate and become post-tropical on Friday, an insurgence of dry air eroding any convection, or shower and thunderstorm activity, while an uptick in wind shear stretches and contorts the dying system.

The new supplemental storm name list

If a tropical storm or hurricane develops in November, it will be named Adria, drawing from the new supplemental storm name list.

Last year and in 2005, when the conventional storm name lists were exhausted, the Hurricane Center referred to additional storms using Greek letters, a practice that ended effective this year.

The World Meteorological Organization (WMO), which is responsible for developing and maintaining storm name lists, found that some Greek letters, like Eta and Zeta, sound too similar, resulting in messaging challenges, and also noted that translating Greek letters into various languages caused hiccups.

Also, as the WMO retires the most devastating storm names, it was put in the awkward position of having to retire Greek letters in 2020, which would not be a sustainable practice as more and more letters were eliminated.

Why so many storms?

In an era when storms are made more intense by climate change and high-impact weather events are becoming more frequent, one might expect an apparent uptick in tropical cyclone incidence would be linked to climate change. Studies, however, do not project an increase in the number of storms due to rising temperatures, just an increase in their intensity.

The number of storms in a given year is most influenced by the prevailing weather pattern.

La Niña, a cooling of ocean waters in the tropical east Pacific, stacked the deck for more storms this year. While La Niña tends to cause sinking air in the Pacific, reducing storm development, it induces broader rising motion over the Atlantic, supporting storm formation.

In addition, improved satellite technology has resulted in more storms being detected in recent years, increasing the likelihood of running through the storm name list.

Jason Samenow contributed to this report.