Atlantic hurricanes are intensifying faster and more frequently, research finds

The list of major hurricanes that rapidly intensified before hitting the United States in recent years is long and memorable: Harvey, Irma, Maria, Michael, Laura, Ida, Ian and Idalia.

All of those storms, starting in 2017, developed explosively over the Atlantic Ocean. Generally, this rapid escalation is increasingly recognized as part of a global phenomenon related to climate change and its associated warming of ocean waters — but until the past couple of years, the Atlantic’s inclusion in the trend was somewhat murkier.

Now, research shows that this rapid intensification is on the rise across the Atlantic basin at multiple time scales. The author of a study published Thursday, Andra Garner, an assistant professor at Rowan University in New Jersey, also highlights regions in which this intensification has become more likely, such as the western Caribbean Sea.

“These findings really just serve to quantify a phenomenon that is very much expected in a warmer climate,” Garner told The Washington Post. “The increased likelihood for hurricanes to transition from weak storms into major hurricanes in 24 hours or less was particularly striking.”

Studies like this will be crucial in unlocking puzzles regarding intensity fluctuations in tropical cyclones. Even as hurricane forecasting improves, intensity and rapid changes in storms are still poorly understood, but understanding them is critical for saving lives and property.

The United States has seen a remarkable increase in economic damage from hurricanes over the past century because of coastal development and population growth, according to the National Hurricane Center.

When it comes to hurricanes and climate change, the most readily detectable shifts can be seen in higher storm surges — or the wind-driven increase in ocean water above normally dry land at the coast — because of sea level rise, heavier rainfall rates and greater occurrence of the most intense types of storms.

The study of rapid intensification — generally defined as an increase in peak winds of at least 35 mph in 24 hours — is still in relative infancy.

While many storm studies are limited to a portion of an ocean basin, Garner examined the North Atlantic as a whole. Using historical data from 1971 to 2020, she was able to assess intensification rates achieved by storms during a 12-, 24- or 36-hour window.

By breaking the data into periods running from 1971 to 1990, 1986 to 2005 and 2001 to 2020, Garner was able to examine intensity changes in different eras.

“Results indicate broad increases to observed (tropical cyclone) intensification rates over the past 50 years,” the study finds.

More specifically, Garner finds that the average maximum intensification rates increased by nearly 29% in the 12-hour window, more than 27% at 24 hours and more than 26% in the 36-hour time frame.

Putting actual wind numbers behind the idea makes it even more stark. The study finds that it’s now as likely that storms see peak winds increase at least 57 mph in 24 hours as it was during a 36-hour period several decades ago.

It was also found that certain parts of the Atlantic have become more prone to rapid intensification in recent decades.

This includes much of the Caribbean Sea, Atlantic waters to the west of northern Africa, and areas near the southeastern U.S. coast. While changes are perhaps most notable in the 24-hour period, they are relatively consistent across all windows.

On the flip side, Garner’s research suggests that rapid intensification has become less frequent in much of the Gulf of Mexico and in an area just east of the Caribbean. Nonetheless, the toasty waters are still engines of explosive development.

Another study published in Geophysical Research Letters recently also addressed the topic.

“Comparing 1980-2000 versus 2001-2021 . . . the basinwide number of (rapid intensification) events has increased by 36%,” the authors wrote in the article published in late August.

That separate research found that the increase in rapid intensification was greatest in the Yucatán and western Caribbean Sea region, as well as the southern North Atlantic. More broadly, it was concluded that intensification rates are faster in the western Atlantic than other parts of the basin.

Sam Lillo, a meteorologist and co-developer of a computer program that can analyze tropical activity worldwide — the Tropycal package in the programming language Python — generally concurs with the findings.

“I can definitely corroborate that there has been an increase in the number of category 1 hurricanes rapidly intensifying to category 3 and stronger,” Lillo wrote in an email. “The message in the western Caribbean is certainly consistent.”

Lillo thinks the trends are driven largely by warmer waters but pointed to additional factors such as whether La Niña (which tends to increase storm activity) or El Niño (which tends to decrease storm activity) is dominant. In most of the regions frequented by tropical cyclones, Lillo calculated an increase in rapid intensification at 24-hour time scales.

Garner, the author of the study released Thursday, hopes to continue investigating changes in intensification, given its increased importance in discussions about preparation. Opening the study up to other basins also may be possible.