March 19, 2021

The 2021 Hurricane Season Effectively Starts On May 15 And Ditches The Greek Alphabet


Big changes are coming to the 2021 Atlantic hurricane season. After an active couple of years, meteorologists are (to their great credit) making some quick and necessary changes to make it easier to keep track of future storms, including unofficially moving the start date for the hurricane season and ditching the use of the Greek alphabet as a fallback. Here's a rundown of the changes you can expect to see beginning this season.

Hurricane Season (Effectively) Moves To May 15th


Beginning this year, the National Hurricane Center (NHC) will initiate their twice-daily tropical weather outlooks beginning on May 15. These outlooks normally don't start until the first day of hurricane season on June 1, but we've seen the year's first named storm develop before that date every year since 2015. This change effectively moves the beginning of hurricane season to May 15th without actually adjusting the start date...yet.

Back in February, the World Meteorological Organization (WMO), the United Nations' agency tasked with maintaining global meteorology standards, wrote a recommendation that the NHC should consider moving the start of the Atlantic hurricane season from June 1 to May 15—a proposal this humble blog made two years ago. We've seen the Atlantic's first named storm develop before the beginning of the season every year since 2015.

By moving regular tropical weather outlooks from June 1 to May 15, the NHC is effectively moving the start date of the Atlantic hurricane season without officially moving the date up a few weeks. It's a wink and a nod that doesn't make a big splash.

Atlantic hurricane season currently runs from June 1 to November 30. These dates are based on when conditions are most likely to allow tropical cyclones to develop and the fact that almost all storms on record formed between those two dates. Since 2003, we've seen 14 named storms form before the official beginning of the season, with each of the last six hurricane seasons recording a named storm in April or May. (2016 also saw an oddball hurricane in January.) Last year, which was the most active hurricane season on record, saw its first two storms form during the final weeks of May.

Many of these preseason storms formed close to land. Tropical Storm Arthur and Tropical Storm Bertha both brought nasty weather to the Carolinas in May 2020. Topical Storm Alberto made landfall in Florida in May 2018. Tropical Storm Bonnie hit South Carolina in May 2016. Even though these preseason storms were relatively weak, they prompted tropical storm warnings and forced coastal residents to go through the motions a few weeks before the season officially began.

Meteorology is a conservative field. I don't mean politically conservative—it's conservative in its habits. Traditions must be followed. Entrenched meteorologists don't like change. Big changes, when they're allowed, usually move at a glacial pace and lots of professionals bristle at the thought of change at all because we do things the way they've always been done, and that's that.

Resistance to change is deep. Heck, even big changes to a snowfall or hurricane forecast are done in increments. And now, after six straight years of storms forming before the start of hurricane season, there's momentum toward changing our artificial timeline that nature doesn't quite follow. It's admirable that the NHC and WMO are receptive to change and reacted to previous seasons by implementing new practices so quickly.

That's why this next change is even more impressive.

The Greek Alphabet Is Gone


Beginning with the 2021 hurricane season in both the Atlantic and eastern Pacific basins, forecasters will no longer rely on the Greek alphabet to name storms once the official list of names is exhausted. The WMO determined that using Greek letters as a backup was confusing, distracting, and bad practice since some of these surplus storms might need to be retired.

Hurricane names are a big deal. They're not all that important when you consider that the storm's hazards should be the sole focus, but we're human. Humans are obsessed with process stories. Hurricane names are important for tracking and communications, and they're culturally significant for the affected areas. 

Tropical cyclone names in the Atlantic basin come from a predetermined list of 21 names that are in alphabetical order (excluding Q, U, X, Y, and Z) and alternate between masculine and feminine. There are six different lists of names. Each list is used every six years, so 2020's list of names will be used again in 2026, and 2021's list of names was last used in 2015.

Since there are only 21 names for a season, we run into a problem if we see 22 or more named storms in one year. We've only dealt with that twice—for the first time in 2005 and again in 2020. The fallback for exhausting the official list of names was to begin using the Greek alphabet to name the 22nd storm and any storms that formed thereafter.

Names are retired when a storm causes so much death or destruction that it would insensitive and confusing to continue using that name again. Andrew, Dennis, Katrina, and Sandy are all some of the dozens of names that were retired. This is also why we don't use Q, U, X, Y, or Z—there simply aren't enough common names to use as replacements.

But what happens when a storm named after a Greek letter needs to be retired? The official line going into that unprecedented back-half of the 2020 hurricane season is you can't retire a Greek letter and a letter used to name a particularly bad storm would continue being used in the future if needed. We dove nine letters deep into the Greek alphabet in 2020, and the final two storms—Hurricane Eta and Hurricane Iota—slammed into Nicaragua as a category four and a category five, respectively.

Given the destruction those two storms caused, the WMO decided that using Greek letters as a fallback wasn't tenable, so they developed two supplemental lists that'll be used as a backup in case we see another season like 2005 or 2020.

The supplemental lists will only be used if the official list of names is exhausted, and any of the included names can easily be retired and replaced if necessary. We'll probably go many years without ever having to think about these lists again. (Oh, and if this system was in place for the 2020 season, we would've gone up to Isla on the new list.)


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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I ran Gawker's The Vane for two years and I've contributed to Mental Floss, Forbes, Popular Science, and the Washington Post's Capital Weather Gang. I also teamed up with Outdoor Life to write a book called The Extreme Weather Survival Manual, which came out in October 2015.

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