May 24, 2024 - Energy & Environment

"It's not just one factor:" Why this hurricane season could be so prolific

Line chart showing average sea surface temperatures for the North Atlantic Ocean Basin. 2024 exceeded all previous years, including the earlier record highs of 2023. On April 29, 2024, the record streak of 421 days ended with an average temperature of 20.83°C, down from the 2023 record of 20.89°C. On May 22, 2024, it was 21.9°C.
Data: Climate Reanalyzer; Chart: Tory Lysik/Axios Visuals

This is not going to be your typical Atlantic hurricane season.

The big picture: On Thursday, the last forecasting domino fell when the official U.S. government outlook from NOAA revealed its most aggressive seasonal forecast on record.

Why it matters: NOAA scientists and those outside the agency are all on the same page, pointing to a rare confluence of factors likely to keep coastal residents on edge from June through November.

By the numbers: The estimates themselves are concerning, though NOAA officials were quick to emphasize preparedness over panic.

  • NOAA is forecasting 2024 will bring 85% odds of an above-normal season, with a 70% probability of 17-25 named storms of tropical storm intensity or greater, eight to 13 of which will become hurricanes, and four to seven major hurricanes of Category 3 or greater.
  • "It's reason to be concerned, of course, but not alarmed," said National Weather Service director Ken Graham, who previously headed up the Hurricane Center in Miami.

Stunning Stat: For perspective, there are only 21 names on the list for 2024, after which NOAA turns to a supplemental list approved after the hyperactive 2020 season.

  • The first storm on the main list is Alberto, and on that extra list the first would be Adria.

The intrigue: Graham, along with outside scientists contacted by Axios, made clear that every ingredient known to influence seasonal hurricane activity is pointing to a near-record one.

  • The North Atlantic Ocean Basin is record warm overall, with deep, bathtub-like waters abundant especially in the Caribbean and the Main Development Region, where many of the fiercest hurricanes roam.
  • Signs show that wind shear, which occurs when winds blow at different speeds and/or direction with height, is likely to be less abundant this season. That's because of a developing La Niña climate cycle in the equatorial tropical Pacific Ocean.
  • "The combination of both the [warm] Atlantic and the La Niña is the crucial aspect here," Suzana J. Camargo, a researcher at Lamont-Doherty Earth Observatory at Columbia University, told Axios via email.
  • "Having both factors acting in tandem is what is pushing these forecasts," she said, noting the many other forecasting groups that match the direction of NOAA's projections.

Between the lines: Lastly, projections show the development of an active West African Monsoon season, which would send numerous clusters of thunderstorms spinning westward off the coast of Africa.

  • These can serve as the seeds of tropical storms and hurricanes.
  • If the season plays out as projected, it would present an opening for the atmosphere to show off the climate change-linked trends, with potentially unprecedented and calamitous outcomes.
  • These include more storms undergoing periods of rapid intensification, reaching higher intensities and delivering more rainfall than they would have just two decades ago.

Threat level: While a seasonal outlook can only project the numbers of storms, not their destinations, this season would have a significant economic impact if there are even just one or two landfalling major hurricanes, of Category 3 or greater intensity, in the U.S.

  • Category 4 Ian, which struck southwestern Florida in 2022, for example, caused $53 to $72 billion in insured losses. It also hastened an insurance company exodus from the Sunshine State.
  • There is also the potential for storms in the Gulf of Mexico to shut down or damage oil and gas infrastructure, leading to price spikes that could hit during summer driving and the height of the presidential campaign.

What we're watching: This season will mark the debut for many AI-based weather forecasting models.

  • They will face key forecast performance tests in how well they predict storm track and intensity when compared to the current generation of forecast tools, most of which also incorporate some AI and machine learning methods.

The bottom line: The ingredients that forecasters have zeroed in on for 2024 are, in a rare instance, all pointing in the same direction.

  • "It's not just one factor, everything has to come together to get a forecast like this," Graham said.
  • "You have all the energy in the oceans, with an active African Monsoon, check, check. Don't expect a lot of shear, check."
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