After a lull, hurricane season is set to come roaring back

This year's hurricane season began ominously enough — with warnings from Canadian and U.S. forecasters that it was going to be rougher-than-normal season, and Hurricane Beryl plowing through the Caribbean as the earliest Category 5 storm in history.

But then, with the exception of Ernesto, the season's been quiet through July and August. In fact, the last time there was such a gap in named storms in August and September was 1968: over half a century ago.

That's about to end.

"By about a week from now, into the middle of the middle of September, the frequency of hurricane activity will increase quite significantly," said Chris Fogarty, manager of the Canadian Hurricane Centre. 

"We're starting to see the weather patterns shift now."

Hurricane Francine, currently at Category 1, is expected to keep strengthening as it heads to the Louisiana coast on Wednesday. Meanwhile, two other storms forming in the Atlantic, according to U.S. and Canadian trackers.

What caused the lull?

Those weather patterns, which kept hurricane activity down, could be due to several factors. Scientists are looking closely at the West African monsoon, which has travelled farther north than is normal. 

The monsoon interacts with a group of heavy clouds in the Atlantic Ocean called the Inter-Tropical Convergence Zone, and these clouds have also been pushed farther north than they usually are, away from ideal conditions for forming hurricanes. Fogarty said it's still not clear why exactly this has happened, but it has impacted the hurricane season.

Dust from the Sahara desert in Africa could also be a factor, as it makes the air drier. That discourages storms from forming, and this year it has persisted into August.

But all these conditions are now slipping away, and the storms seem set to come roaring back.

"Getting to the middle of September, and we're starting to see the weather pattern shift to more typical hurricane season conditions," Fogarty said. 

"So once we get to the latter half of September, October is probably going to be pretty busy in the Atlantic region."

What does it mean for Canada?

Matt Rosencrans, lead hurricane season forecaster with the U.S. National Oceanic and Atmospheric Administration, says the peak of the hurricane season is usually around now, in early September. 

This year, with the earlier lull in storms, that peak might get pushed later.

"Which means that October, November could be really active," he said.

And that means that those storms would come around the same time as winter-time low-pressure systems that could sweep the storms up to the Maritime provinces, he said.

Hurricane Fiona in 2022 formed in somewhat similar conditions, in mid-September, after a quiet August. Fiona was the one of the costliest storms in Canadian history, causing $800 million in insured damages across the Atlantic provinces, according to the Insurance Bureau of Canada.

Right after Fiona, Hurricane Ian hit the Caribbean and southern U.S, and became one of the costliest disasters worldwide, causing damage worth $150 billion, according to NOAA.

"That's usually my concern when I see it really quiet for a while," Fogarty said. 

"The atmosphere and the ocean are probably ready to explode with storm activity."

Will the lull happen again?

Rosencrans is watching all the factors affecting storms this year for any clues about the role of climate change — and any longer-term changes in how hurricanes behave.

He says if climate change alters how the monsoon in West Africa behaves — moving permanently more north, for instance, it could change the hurricane season in the Caribbean. 

"Given climate-change scenarios, if the Sahara is going to get a degree or two warmer, is that going to continually pull the monsoon further north?" 

While the number of storms is not increasing, climate change is causing the storms to be stronger — and intensify rapidly. 

In fact, with storms getting more intense, scientists are even considering whether to add a Category 6 to better reflect the strength of these hurricanes (they currently max out at Category 5).

This year's season will add to scientists' understanding of how the storms are changing, and perhaps help improve storm prediction and the ability to prepare for them.

"It's just going to take time and effort, from myself and the other scientists around the world that are dedicated to this," Rosencrans said.

"I want to be able to tell people so that they can plan and get themselves in a safer position."