For the first time in more than a decade, forecasters with the National Oceanic and Atmospheric Administration have issued a pre-season hurricane outlook calling for a slow season. But that prediction landed with a major caveat: odds of being correct clocked in at just 55%.
The nearly 50-50 probability is being driven by a complex set of factors, including a major El Niño potentially reaching historic proportions, a busy monsoon season and ongoing ocean warming driven by climate change.
”We've had years where we've had stronger probabilities and lower probabilities,” NOAA lead hurricane forecaster Matt Rosencrans said during last week’s hurricane briefing. ”So we've calculated all those uncertainties in there, and that's why we came up with the 55 percent.”
What’s not clear is whether the monsoon season on the African coast where hurricanes are born will out perform the El Niño, which can prevent storms from strengthening.
Forecasters are calling for above average rain in the region, which would normally spawn more hurricanes. But with a 98% chance of an El Niño appearing next month — and predictions that it will reach epic intensity — there’s a good chance that storms will get shredded by the upper atmospheric wind shear generated by the El Niño before they can become more intense cyclones.
Still, forecasters worry that ocean temperatures that now regularly rise above normal as climate change warms the planet present another layer of complexity.
”You produce that wind shear, you make it harder for those storms to develop. But it also does mean that some of those storms that do get closer to the coast can hit that warmer water, can hit a pocket of low shear, and then they can take off,” Rosencrans said.
If the forecast plays out as predicted, it would make the second year in a row for a slow season, after nearly a decade of remarkably busy seasons. In 2020, a record 30 named storms churned out of the Atlantic. To reflect the increasing number of storms, the National Hurricane Center adjusted the definition of a “normal” hurricane season in 2021 by increasing the average from 12 from 14 named storms and six to seven hurricanes.
The increase partly reflected improved technology that can better detect storm systems, NOAA said. But the agency also blamed the increase on climate change.
“NOAA scientists have evaluated the impacts of climate change on tropical cyclones and determined that it can influence storm intensity,” Rosencrans said at the time.
Last year, even while the season generated a below average number of storms, three of five major hurricanes blossomed into powerful Cat 5 storms. Four underwent rapid intensification, when a storm can gain more than 35 mph in wind speed in under 24 hours. Hurricane Milton exploded with a 90 mph increase in speed in under 24 hours, spinning from a tropical storm with 60 mph winds to a Cat 4 with 150 mph sustained winds.
“The public thinks the big storms are gonna come across the Atlantic, you're gonna see them, you're gonna have weeks notice, plenty of time,” said National Weather Service Director Ken Graham. "That is not the case."
“The public thinks the big storms are gonna come across the Atlantic, you're gonna see them, you're gonna have weeks notice, plenty of time. That is not the case."National Weather Service Director Ken Graham
Another risk from a more intense storm can be its destructive reach, even after making landfall. Hurricane Helene delivered record flooding in North Carolina nearly 400 miles from where it made landfall near Perry, in Florida’s Big Bend. To better predict those hazards, the hurricane center is rolling out a suite of new tools this season.
”The impacts don't stop at the coast. The effects go way inland. And we've seen that over and over and over again, including most of the fatalities,” Graham said. ”There's no such thing as just a Cat 1, just a tropical storm, just a Cat 2….Even the smallest storm, if it's slow enough and big enough, it's gonna create catastrophic flooding and storm surge.”
