For the past 27 years, without fail, the Labor Day holiday weekend in the US has featured a storm in the Atlantic – but not in 2024. In early September, the Atlantic basin remained suspiciously quiet, continuing a run of calm weather that has lingered since Hurricane Ernesto whipped through the Caribbean in mid-August.
Hurricane forecasters were almost certain this year would be a busy hurricane season in the Atlantic, says at Colorado State University, who co-authors the institution’s influential hurricane forecasts.
Waters in the equatorial Pacific are cooling, marking a global shift to a La Niña weather pattern, which generally favours a more active hurricane season. The Atlantic Ocean is also still experiencing near-record levels of heat, providing fuel for developing storms. Against that backdrop, delivering a forecast for a busy season was “like shooting fish in a barrel, super straightforward”, says Klotzbach.
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In June, Colorado State University issued an “extremely aggressive” forecast, according to Klotzbach, predicting 25 named storms and 12 hurricanes for the 2024 season. In May, the National Oceanic and Atmospheric Administration (NOAA) in the US predicted between 17 and 25 named storms and up to 13 hurricanes.
But so far this season, which is now almost halfway through, only three hurricanes have appeared: Beryl, Debby and Ernesto, plus two named storms below hurricane status, Alberto and Chris. Where have the storms gone?
The building blocks of a busy storm season – a transition to La Niña and high ocean temperatures – are still there, says Klotzbach, but the system isn’t responding as expected. “A lot of the stuff we expect has been there, it just hasn’t produced the storms. That’s more the surprise.”
A few factors are at play. Despite ocean temperatures across the Atlantic basin persisting at near-record highs, one stretch of water near the equator has cooled rapidly to below-average levels. That may have helped push Africa’s monsoon band – known as the Intertropical Convergence Zone – much further north than usual, says Klotzbach, bringing heavy rain to parts of the Sahara desert that normally stay hot and dry.
“This is a very unusual pattern,” says at forecasting service AccuWeather. The result is that tropical waves, the seedlings of storms, are being pushed off the African coast far further north than normal, over the colder waters of Western Sahara. “That tends to squelch your storms,” says Klotzbach.
Tropical waves travelling over the Sahara are also picking up dusty, dry air. On 3 September, the European Union’s climate service Copernicus said . “For hurricanes to develop, you need moisture,” says at the University of Miami in Florida. “This deep layer of dry air coming off Africa into the Atlantic prevents the storms from really kicking off.”
There are other reasons too. Although La Niña is developing, it hasn’t happened as fast as expected, says Da Silva, so the wind conditions for hurricanes haven’t been quite as optimal as forecasters thought.
Meanwhile, a weather pattern known as the Madden-Julian oscillation has brought dry weather over the Atlantic since late August, says Kirtman. The oscillation has “fully enveloped into the Atlantic now”, he says, suppressing storm activity.
“It’s definitely weird,” says Klotzbach. “Everything looks kind of anaemic out there.”
at NOAA says the agency will perform a rapid attribution analysis later this year to determine why the African monsoon band pushed so far north. He also suggested that high temperatures in the troposphere were a key factor in suppressing storms, along with the record-breaking land and air temperatures in the past two years fuelled by climate change. “We’re seeing global temperatures that we’ve never seen before, so to have patterns that emerge that we’ve never seen before, it doesn’t seem like too big of a stretch,” he says.
The Atlantic hurricane season reaches its peak around 10 September, so forecasters say it is too early to declare the season an anticlimax. The progression towards La Niña is picking up pace, creating the right conditions for storm formation. Meanwhile, ocean waters, particularly around the coast, remain extremely warm. That lays the groundwork for storms to rapidly intensify once they do develop, says Da Silva.
“I’m concerned that the second half of the season could ramp up,” he says. “The warm waters are still there – if anything, they are warmer than when Beryl went through. So it’s just going to take one storm to come through there… and we could be looking at another major hurricane.”
The changing climate escalates this risk. While it is still unclear whether a warming world will produce more storms, research shows that it increases the chances of hurricanes rapidly intensifying, leaving communities with little warning before a savage storm hits. Climate change can increase the volume of rain dumped by a storm and increase the severity of storm surges, in both cases raising the risk of dangerous flooding.
“There are lots of impacts of hurricanes that we know are getting worse,” says at Rowan University in New Jersey. “Even if this season is not yet quite as active as we thought, as we warm the planet we are still stacking the deck for the possibility of a hurricane to be very intense.”
