Atlantic Ocean | Hurricanes twice as likely to become major

With warming oceans serving as fuel, Atlantic hurricanes are now twice as likely as before to rapidly intensify from minor hurricanes to powerful, catastrophic hurricanes, study finds published Thursday.

Last month, the hurricane Lee went from being a low-intensity hurricane (with winds of 129 km/h) to a Category 5 monster, with winds of 249 km/h, in just 24 hours. In 2017, before devastating Puerto Rico, the hurricane Maria went from a Category 1 storm with winds of 145 kilometers/hour to a Category 1 hurricane with winds of 257 km/h in just 15 hours.

The study looked at 830 Atlantic tropical cyclones since 1971. It found that over the past 20 years, 8.1% of storms went from minor Category 1 storms to major hurricanes in for 24 hours only. This only happened 3.2% of the time between 1971 and 1990, according to the study published in the journal Scientific Reports.

Category 1 hurricanes generate winds of up to 153 km/h and a hurricane must have winds of at least 178 km/h to be considered major.

These are the most extreme cases, but the fact that the rate of intensification has more than doubled is worrying, said study author Andra Garner, a climate scientist at Rowan University, in New Jersey.

When storms intensify quickly, especially as they approach land, it is difficult for people in their path to decide whether to evacuate or hunker down. It is also more difficult for meteorologists to predict the size of the storm and for emergency managers to prepare, Garner and other scientists.

“We know that the strongest, most damaging storms very often intensify very quickly at some point in their life,” Garner, talking about 2017’s Storm Maria, which some researchers say killed nearly 3,000 people directly and indirectly. This is a difficult phenomenon to predict and can certainly lead to a more destructive storm. »

And this phenomenon “has become more common over the last 50 years,” added Garner. All of this happened during a period when ocean waters warmed. »

“90% of the excess warming that humans have caused to the planet has ended up in our oceans,” she recalled.

This year, the oceans have been setting heat records every month since April, and scientists are warning of unusually high temperatures.

Mme Garner found that the rapid intensification of hurricanes primarily affected the Atlantic coast of the East Coast, more so than the Gulf of Mexico.

This is not just about cases of extreme rapid intensification. Mme Garner looked at all the storms over different time periods and found that, in general, they are intensifying faster than before.

In recent decades, Atlantic storms have been more numerous than in the 1970s and 1980s. Scientists have several theories to explain this phenomenon, ranging from the evolution of air pollution to natural cycles, but Mme Garner explains that by looking at percentages, she eliminated the factor of storm frequency.

Previous studies have found an increase in rapid intensification. According to Karthik Balaguru, a climatologist at the Pacific Northwest National Lab, who published a paper last year showing that storms near the Atlantic coast intensify more quickly before making landfall than in the 1970s and 1980s, the study Mme Garner is statistically meticulous and confirms what scientists already understood.

The U.S. National Hurricane Center considers a storm to intensify rapidly if wind speed increases by 28 mph (46 km/h) in 24 hours.

In 2020, record year for hurricanes and final year of M’s studyme Garner, six storms intensified this quickly: Hannah, Laura, Sally, teddy, Gamma And Delta. Since then, several deadly storms have intensified rapidly, including Ida in 2021, Ian in 2022 and Idalia in 2023.

“If we do not work to reduce our emissions [de carbone]we could expect this trend to continue in the future, or even get worse, warned Mme Garner.

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