30 Storms in a Record Hurricane Season; Here's How Many More Could Form

Monday night, Subtropical Storm Theta became the 29th named storm of the 2020 Atlantic hurricane season, topping the previous record of storms in any season, 28, set in 2005.

We now have Tropical Storm Iota over the Caribbean Sea that is likely to strengthen soon into a hurricane. It is the 30th named storm of 2020.

Thirty named storms in one hurricane season. Let that sink in for a moment.

The average number in any season is only 12 to 13.

So, how many more storms could form the remainder of this historic hurricane season?

Past Novembers, Decembers, Januaries and Februaries

From 1950 through 2019, 35 storms have formed in November, an average of one storm every other year.

So, we've already met that November benchmark in 2020.

In that same 70-year period, 10 storms formed in December, and four storms formed in either January or February.

The last storms to form after the official hurricane season's end of Nov. 30 were Hurricane Alex in January 2016 and an unnamed tropical storm in early December 2013.

How More Active Seasons Ended

Let's examine past seasons that were as active or more so than 2020 to see how many delivered more storms from this point on.

According to Colorado State University tropical scientist Phil Klotzbach, only three other years had more named storm days than 2020: 2005, 1995 and 1933. Named storm days, by the way, are just as they sound. For each 24-hour period a system is at least a tropical or subtropical storm, it counts as one named storm day.

-2005: 4

-1995: 0

-1933: 1

The previous record-holding season for storms, 2005, produced Gamma, Delta, Epsilon and Zeta after Nov. 10, with Zeta lasting until early January 2006.

If the 2020 season ended like 2005 with four more storms, our season total would end up with an unfathomable 33 storms, taking us halfway through the Greek alphabet ending with Mu.

Another way to look at this is through a metric called the ACE index.

Short for Accumulated Cyclone Energy, ACE takes into account not just the number but also the intensity and longevity of storms and hurricanes.

According to data compiled by Klotzbach through Nov. 9, there have been only 21 hurricane seasons with a higher ACE index than 2020.

Eleven of those 21 seasons had at least one additional storm form after Nov. 10, with numbers of additional named storms ranging from one to four.

There is a historical precedent for the list of storms to climb a few more notches before we can finally close the book on the 2020 Atlantic hurricane season.

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