After triggering widespread flooding and power outages for half of Puerto Ricothis season’s third hurricane, Ernesto, turned north, approaching Bermuda. In an average Atlantic season, the third hurricane will not appear until September 7so Ernesto arrived very early. From August 9 this summer has already a third of the activity produced in a typical season — with nearly 90 percent of it left.
All of which makes Ernesto, now a Category 2 hurricane, an ominous sign of what’s to come in the next few months — and what to expect as the planet warms rapidly. “To be a little more than three weeks ahead of schedule for the third hurricane is pretty impressive,” said Brian McNoldy, a hurricane researcher at the University of Miami.
this spring, scientists predict that the Atlantic Ocean would play host to an unusually active hurricane season, with five major hurricanes and 21 named storms, for one particularly good reason – the ocean is unusually warm, and it is expected that stay that way. In July, the nursery for Atlantic hurricanes was underway 2.8 degrees Fahrenheit higher than the long-term average. “Hurricanes are a lot like engines — they need some kind of fuel,” said Daniel Gilford, who studies hurricanes at Climate Central, a nonprofit research organization. “They need something to be able to accelerate and pick up wind speed, and the thing they use to do that is primarily the ocean surface.”
As water evaporates from the ocean, drift clouds form that release heat and lower atmospheric pressure. It sucks in air and creates winds and a vortex. Hurricanes also like high humidity because dry air can slow the speed of the updraft that the storms need to grow large and strong. Hurricanes hate wind shear – winds moving at different speeds and directions at different altitudes. El Niño tends to encourage the spread of wind shear across the Atlantic, while La Niña tends to discourage it. Right now, conditions are “neutral” as El Niño has faded and La Niña has not yet officially formed.
So warm ocean temperatures aren’t the only ingredient in making a hurricane, but it’s certainly the fuel. As Ernesto raced across the Atlantic between West Africa and the Caribbean, it encountered abnormally high ocean temperatures made at least 50 to 100 times more likely by climate change, according to Climate Central’s analysis. (To be clear, this is not saying that Ernesto itself was more likely due to climate change—that would require further analysis.) Even more remarkably, the group found that Hurricane Beryl, a Category 5 hurricane that hit Texas in early July made, fed on ocean temperatures 100 to 400 times more likely through climate change. “We also know that storms move slower, they last longer, and we expect these things to be affected by climate as well,” Gilford said.
High ocean temperatures also fuel the “rapid intensification” of hurricanes, defined as a jump in sustained wind speeds of at least 35 mph in 24 hours. Hurricane Beryl did it on its way to Texas, breaking records for how quickly it developed into a monster storm. Rapid intensification makes hurricanes extra dangerous because a coastal city might be preparing for a Category 2 to make landfall, only for a Category 5 to suddenly appear. And the problem is only getting worse, as research has found a dramatic increase in the number of rapid intensification events near the coast.
Fortunately for Bermuda, Ernesto has not intensified quickly – although it came close this week – but it is still a very dangerous Category 2. “The shear may be a bit stronger than originally thought,” said Samantha Nebylitsa, who studies hurricanes at the University of Miami, and “dry air has only hindered the intensification. It just won’t let up.” It could weaken the storm to a Category 1 by the time it hits Bermuda.
The Atlantic will likely continue to provide more fuel as the summer winds down. Because the ocean takes longer to warm up than the land, the peak of the hurricane season is only in September. And the season doesn’t officially close until the end of November. “The best forecasts suggest that we’re maybe only about 15 or 20 percent of the total activity that we expect this year,” Gilford said. “There’s a lot more to come in the pipeline in 2024.”
