JACKSONVILLE, Fla. – The 2020 hurricane was the third most active season, but numbers don’t always reveal the complete picture. Although there were 21 storms this year, several were weak systems lacking longevity. A few gutless storms lasted less than 36 hours but still boosted the overall storm count.
There have been more powerful hurricane seasons compared to this one which ranks as the 25th most energetic on record.
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The scorecard is something called the accumulated cyclone energy index. Every cyclone has an ACE value, which is a number based on the maximum wind speed measured at six-hour intervals over the entire time that the cyclone is classified as at least a tropical storm (wind speed of at least 39 miles per hour).
Therefore, a storm’s ACE index value accounts for both strength and duration.
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The National Oceanic and Atmospheric Administration calculates the total ACE index value for an entire hurricane season by adding the values for all named storms, including subtropical storms, tropical storms, and hurricanes.
Abundant storms do not always equal an extremely energetic or powerful storm season if they are weak and short lived.
Compare, the 2017 season which produced just 17 named storms, but resulted in the 5th most energetic season on record.
To assess the activity of the year, it is important to analyze overall storm strength and duration from one year to the next. The total accumulated energy of a tropical cyclone, measured by the ACE index, can be used to calculate this for each hurricane season.
The ACE index is one of the most comprehensive comparison methods.
This season finished at the top 25 position. The total 145.1 ACE produced this season has been above average but slightly less than last year.
In contrast, the 2020 Atlantic hurricane season had 179.8 ACE, placing it in the ‘extremely active’ category and ranked in the Top-13 Atlantic hurricane ACE seasons. The record-breaking number of tropical storms and hurricanes helped boost the ACE.
- Extremely active – ACE above 152.5
- Above-average – ACE above 111
- Near-average – ACE between 66 and 111
- Below-normal – ACE below 66
Much of the accumulated energy was racked up by major hurricanes Larry and Sam. Both had considerable ACE and fortunately these stayed out at sea during September and the early part of October.
The record holder hurricane season is still 1933, with an ACE of more than 258 followed by the 2005 hurricane season. It had the second most named storms after 2020 and ended up with an extremely high ACE of 250.