An analysis by AccuWeather meteorologists and scientists shows that while the overall intensity of hurricane seasons appears to be trending downward, the storms that gain hurricane strength have been growing stronger.

The simple answer to what is driving this trend lies in the fact that there is more warm water and warm, moist air in the atmosphere that serve as fuel to help maintain the intensity and strength of the storms. However, the longer answer involves a deeper dive into the data and a look at weather mechanics.

At its core, weather tells the story of a world trying to maintain equilibrium from pole to pole.

“Nature seeks equilibrium. If you put ice in a glass of water, it will eventually come to room temperature,” explained Scott Mackaro, AccuWeather’s vice president of science and innovation from 2019 to 2022. “The poles of the Earth are cold, and the equator is warm. Again, nature will seek equilibrium and attempt to mix everything together. This is the basics of why we have weather.”

Hurricanes serve as an example of this, he added.

“And so hurricanes serve as an extreme example of nature seeking equilibrium. It’s a very natural and very necessary energy exchange mechanism,” Mackaro said.

A closer look at the energy

Mackaro gathered data from between 2020 and 1851, when record-keeping on hurricanes began, and plotted out the ACE Index of each season.

The ACE Index, short for the accumulated cyclone energy index, is a measurement that factors in a hurricane’s intensity by accounting for both its strength and duration. Stronger, longer-lasting storms will score higher than weaker, shorter-lived storms. When the ACE Index totals of each storm in a season are combined, it tells the intensity of the season.

“ACE tells you the tale of the season,” AccuWeather lead hurricane expert Dan Kottlowski said.

If only the ACE Index and time are considered, the resulting graph will show an upward trend in the ACE Index overall. However, this is misleading, Mackaro noted, as developing technology has increased the number of storms scientists and meteorologists are able to observe.