An ‘extremely active’ hurricane season is headed our way, experts warn

The forecast released Thursday is the latest indication that a surge in global heat over the past year, far beyond the gradual warming observed across recent decades, could translate to greater extreme weather risks.

The predictions are so aggressive, they would mean the Atlantic basin could exhaust a list of 21 storm names for a second time in four years, and the third time since 2005. After that, meteorologists would start using a list of supplemental storm names the World Meteorological Association adopted in 2021, replacing a practice of using Greek letters.

The researchers said their hurricane season forecast comes with more confidence than usual, and it includes the highest predictions the team has made in 40 years of producing these outlooks. Although hurricane season predictions aren’t rock-solid at this time of year, sea surface temperatures are so extreme across the Atlantic basin that stormy conditions appear all but assured.

“It would take something pretty crazy for the Atlantic to not be substantially warmer than normal for the peak of the season,” which typically occurs in August and September, said Colorado State University hurricane researcher Philip Klotzbach, the forecast’s lead author. “The signal certainly points quite strongly toward a busy season this year.”

A trend toward a stormier Atlantic

The forecast far outpaces historical averages, but it is in line with several recent hurricane seasons.

In a typical year, about 14 tropical cyclones organize and strengthen enough to become named tropical storms — swirling systems organized around a low-pressure center and with maximum sustained winds of at least 39 mph. About half become hurricanes, on average, with maximum sustained winds of at least 74 mph.

Three of the storms become major hurricanes, on average, with winds of at least 111 mph. This year, the Colorado State researchers predict five major Atlantic hurricanes.

There have been at least 20 named storms in three of the past four seasons, including in 2020 when a record 30 storms got names, nine of them carrying the names of Greek alphabet letters.

Whether tropical cyclones are becoming more frequent isn’t scientifically settled, but there is evidence to suggest that is one consequence of global warming. Research has also shown intense cyclones are forming earlier during hurricane season than they did in the past.

‘Very concerning’ conditions in place

This year, there are two main factors driving expectations of a busy season: Historic warmth across Atlantic surface waters, and an assumption that a La Niña global climate pattern will develop by the hurricane season’s peak in late summer and early fall. Warmth provides more energy for storms to unleash, and La Niña tends to promote atmospheric wind patterns that are conducive to storms’ development.

Record ocean warmth made for an active 2023 hurricane season, with 20 named storms, despite the presence of El Niño, the opposite of La Niña and typically a hindrance to Atlantic cyclone development. While El Niño encourages wind shear in the Atlantic basin — changes in wind speeds and direction at different altitudes — La Niña discourages it, providing an environment for cyclones to develop tall clouds and intense low-pressure centers.

As April begins, the tropical Atlantic is as warm as it would normally be at the start of July.

That means the heat that will drive storm activity could already be all but locked in. If Atlantic temperatures surpass 2023 levels, “that’s very concerning,” said José Javier Hernández Ayala, an associate professor focusing on climatology at Sonoma State University in California.

“We don’t know if these [ocean temperature] trends are going to continue,” he said. “If they do, that’s definitely going to be fueling more activity.”

That said, “having warm water does not guarantee hurricanes,” said Kim Wood, an associate professor of hydrology and atmospheric sciences at the University of Arizona. Storm activity will also depend on the African monsoon season, which can send atmospheric disturbances into the Atlantic that serve as “seeds” for tropical cyclones, they said.

Heightened coastal risks

While seasonal forecasting does not allow meteorologists to predict where storms might go, the conditions expected across the Atlantic raise the odds for landfalling storms in the United States.

The researchers estimate a 62 percent chance that a major hurricane will make landfall somewhere in the continental United States, compared to a 43 percent chance in an average year.

And they estimate a greater than 1-in-3 chance of a major hurricane landfall somewhere on the East Coast, an area where the average chances are about 1 in 5. If La Niña forms as expected, that would raise the risks of storms forming off Africa and sweeping across the Atlantic basin and up the East Coast, Colorado State’s Klotzbach said.

“Your odds of landfall from Florida to Maine go up quite a bit when you have La Niña, because it favors those long-track storms,” he said.

Exceptionally warm waters in the Gulf of Mexico and Caribbean, which have helped drive a growing number of storms to rapidly intensify into major hurricanes in recent years, will likely mean especially high storm risks for islands, including Puerto Rico, Central American countries and the U.S. Gulf Coast, said Hernández Ayala of Sonoma State University.

The conditions are prompting calls to prepare for potentially violent storms. AccuWeather last month warned its audiences that an “explosive” hurricane season could be ahead, predicting 20 to 25 named tropical storms and eight to 12 hurricanes, including as many as seven major hurricanes. The National Hurricane Center is expected to issue its season forecast in May.

Klotzbach said there is still time for conditions to change in ways that could impact storm risks. While forecasters have dramatically improved their skills at predicting hurricane activity so many months out, there is still more uncertainty in April than there will be in June or August.

“It’s a forecast, not a guarantee,” Klotzbach said.