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Residents survey damage and cleanup following Hurricane Francine Thursday, September 12, 2024, in Berwick, La. Facebook Twitter WhatsApp SMS Email Print Copy article link Save The 2024 Atlantic hurricane season is now considered to be "extremely active," making it the 11th season in more than 50 years to reach hyperactive classification. The designation, created by the National Oceanic and Atmospheric Administration, has been used a handful of times since hurricane researchers starting using satellite data in 1966, according to Philip Klotzbach, a hurricane researcher at Colorado State University.
Other extremely active Atlantic hurricane seasons were recorded in 1995, 1996, 1998, 1999, 2003, 2004, 2005, 2010, 2017 and 2020. Klotzbach said this year is above normal in most of the metrics scientists use to determine a season's severity: There have been a high number of named storms, many of which have reached hurricane and major hurricane strength, and many of those have made landfall. "What really has stood out to me about this season has been just how odd it has been," Klotzbach said.
"While we've gotten to hyperactive, it certainly wasn't a 'normal' hyperactive season." A busy end to hurricane season While the Atlantic's most active month is historically September, followed by August, this season's was October, followed by July, according to Klotzbach. The busy end in particular, with a record-breaking number of named storms formed after Sept.
24, helped to push it into the hyperactive threshold. Autumn has been characterized by both below average wind shear and "extremely" warm ocean temperatures in the Atlantic and Caribbean Sea, Klotzbach said, both of which have helped fuel late-in-season storm formation. That, paired with Hurricane Beryl's historically early formation and a peak-season lull that left scientists scratching their heads, have made for a season displaying unusual patterns.
"The fact that we've gotten to hyperactive despite the prolonged lull at the climatological peak of the season is probably what has stood out to me the most," Klotzbach said. The 2024 ACE score NOAA ranks hurricane seasons based on accumulated cyclone energy, or ACE, which considers the duration and intensity of each named storm to form in a season. A hurricane season's overall ACE index is calculated by adding each storm's individual score together.
A near normal season would end on Nov. 30 with an ACE score of 73 to 126, according to NOAA's definition. A season with an ACE of 159.
6 or higher is considered extremely active. Hurricane Rafael's six-day stint as a named storm in early November helped push the 2024 season just over the edge, according to data collected by CSU, bringing its ACE up to 159.8.
This year's accumulated cyclone energy (blue) compared to the average of the last 30 years (purple). There's still a chance this season's total ACE could rise as the rest of the month plays out, or it could be modified higher or lower in the National Hurricane Center's post-season analysis, Klotzbach said. High intensity storms Jill Trepanier, a hurricane researcher and professor at LSU, said 2024's high ACE score correlates with what forecasters predicted would happen: There weren't just a lot of storms, but many of them were severe and rapidly intensified over warm waters.
In May, the National Oceanic and Atmospheric Administration predicted 2024 would bring "above-normal" hurricane activity, with 17 to 25 named storms, eight to 13 hurricanes and four to seven major hurricanes of Category 3 strength and above. “So this particular year, we have had a fair number of named storms, but in general it’s not necessarily the frequency of events that will lead to a very a high ACE," Trepanier said. "It’s really about the intensity.
” Hurricane Beryl, one of the storms that Trepanier said surprised her most this year, generated an ACE of 35.1 after it produced winds of 145 mph and spent nearly 10 days as a named storm, according to data collected by CSU . Helene, despite producing high winds of 120 mph and causing catastrophic destruction far inland in the Southeast U.
S., accumulated a score of just 7.1.
That storm had a short track and spent only 3.25 days as a named storm. “So ACE is good for some things and not representative of other things, like the actual threat to people," Trepanier said.
Eleven of this year's 18 named storms reached hurricane strength, according to data collected by CSU. Five of those peaked as Category 3 storms or higher. Trepanier, whose research at LSU is largely related to hurricane intensity and rapid intensification, said that's a fairly high hurricane conversion rate.
What's not exactly clear to scientists yet is why some seasons produce higher numbers of high-intensity and rapidly intensifying hurricanes. Some research suggests that it has to do with warm ocean waters, particularly when that warmth runs deep, she said. But it could be a number of factors working together or at different times, including moisture in the air and the areal coverage of rainstorms.
"The question of why is it happening is a big one," she said..
