At a Glance

Atlantic hurricane seasons have been particularly active since 2016.A stretch from 2013-15 was the most recent quiet period.There were a number of quieter seasons in the 1980s and early 1990s.

The frenetic 2020 Atlantic hurricane season is just the latest in a string of active seasons. In fact, it's been a while since a hurricane season was relatively quiet.

As of October 14, we've blown through 25 storms, second only to 2005's 28 storms. , shattering a record that had stood for 104 years.

Hurricanes Isaias, Laura and Sally have already been added to NOAA's billion-dollar disasters list in 2020, and .

An aerial view shows floodwaters from Hurricane Delta surrounding structures destroyed by Hurricane Laura on Oct. 10, 2020, in Creole, Louisiana. Hurricane Delta made landfall near Creole as a Category 2 storm in Louisiana initially leaving hundreds of thousands of customers without power.

(Mario Tama/Getty Images)

Hurricane Matthew in 2016 through Imelda in 2019, added up to a responsible for just under $350 billion in damage.

We certainly understand if you've begun to think that every hurricane season is like this.

Fortunately, there are quieter hurricane seasons. It's just been a while since we've been through one.

The Last Quiet Hurricane Season

There are several ways meteorologists measure a hurricane season's activity.

They can count the number of tropical or subtropical storms, hurricanes and those that reach "major" status - at least Category 3 intensity.

In an average hurricane season - in the late 19th and early 20th centuries - 13 storms form, seven of which become hurricanes and three of which become at least Category 3 intensity.

Another metric called the ACE index – short for Accumulated Cyclone Energy – takes into account not just the number, but also the intensity and longevity of storms and hurricanes. A hurricane season with a lot of long-lived, intense hurricanes would have a high ACE. An average season's ACE index is about 106, according to compiled by Phil Klotzbach, a tropical scientist at Colorado State University.

Using all those metrics, it's been five years since the last hurricane season could be thought of as less active than average.

The number of hurricanes (red bars) and ACE index (green line graph) in each Atlantic hurricane season from 2010 through 2019. The last hurricane seasons that were less active than average were from 2013 through 2015.

(Data: Phil Klotzbach, NOAA; Graph: Infogram)

The produced only 11 named storms, less than half of 2020's tally. That was also the year of one of the strongest El Niños on record, which acts to limit tropical activity by generating increased wind shear, particularly over the Caribbean Sea, which can rip apart a weaker tropical system.

Despite only four hurricanes in 2015, stalled and ransacked the central Bahamas, emphasizing the danger even in quieter hurricane seasons.

In 2014, the El Niño hadn't developed yet, but wind shear and sinking air in the tropics only allowed eight named storms to form, the lowest count in any season this century.

However, six of those became hurricanes, including a Fourth-of-July North Carolina strike from Arthur, and back-to-back Bermuda hurricanes Fay and Gonzalo.

2014 Atlantic hurricane season tracks. Only eight named storms formed that season, including Hurricane Arthur, which made landfall in North Carolina on the Fourth of July holiday.

(Data: NOAA, NHC)

Another quiet hurricane season was , another year dominated by sinking air in the tropics.

There were 14 storms that year, but only two of them became hurricanes, tied for the least in any hurricane season in the satellite era (since the mid-1960s). Neither of those hurricanes managed to reach Category 2 intensity, something that hadn't happened in any season since 1968, according to the National Hurricane Center's .

The 2013 season had only one U.S. landfall, Tropical Storm Andrea in northern Florida in early June.

Some other quiet seasons this century included - nine storms, three hurricanes during a weak to moderate El Niño - and - only 10 storms the year following the record 2005 season.

During the cool phase of a 20- to 40-year oscillation of North Atlantic Ocean sea-surface temperature known as the , less active hurricane seasons were quite common in the 1980s and early 1990s.

Eight of the 15 hurricane seasons from 1980 through 1994 produced less than 10 storms.

In 1983, only four named storms formed, the least in any season in the satellite era.

However, three of those four storms became hurricanes, one of which was Alicia, which pounded the Houston metro area at Category 3 intensity.

Only four named storms formed in the 1983 hurricane season, but three were hurricanes, including destructive Hurricane Alicia in southeast Texas.

(Data: NOAA, NHC)

Why So Active Recently?

El Niño's opposite is one factor.

Instead of a warming of the equatorial Pacific water this hurricane season, we've seen a cooling, known as La Niña.

This cooler water ends up causing less wind shear and weaker low-level winds in the Caribbean Sea and can enhance rising motion over the Atlantic Basin as a whole, all making it easier for tropical storms and hurricanes to develop.

The suppressing influence of La Niña in the eastern Pacific Basin, but enhancing influence in the Atlantic Basin.

(NOAA)

Weak La Niñas also developed in the active 2016 and 2017 hurricane seasons.

Another factor in 2020 was the in the tropical Atlantic Basin, making the atmosphere more unstable for showers and thunderstorms needed to develop and maintain tropical storms and hurricanes.

Whether these hyperactive hurricane seasons will become the new normal is a tricky question.

A number of studies over the past several years have found tropical cyclones are and .

found the numbers of tropical cyclones have increased in some parts of the world, yet diminished in others since 1980. However, found little change in the total number of the planet's tropical cyclones over the year.

The ultimate measure of a hurricane season, however, is its impact.

As mentioned earlier, this five-year stretch has generated a dozen storms with major U.S. impact.

Let's hope there may be a quieter season ahead soon, if not by a reduced number of storms, then in fewer storms striking land.

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