Once hurricanes make landfall, they’re lingering longer and staying stronger

Atlantic hurricanes are taking longer to weaken after making landfall than they did 50 years ago, thanks to climate change. Over the past 50 years, increasingly warm ocean waters have juiced up the storms, giving them more staying power after they roar ashore, scientists report in the Nov. 12 Nature. That could potentially extend storms’ destructive power farther inland, the researchers say.

As ocean waters warm, tropical cyclones — called hurricanes in the Atlantic Ocean — are likely to gain in intensity, studies show (SN: 9/28/18). They can also hold more moisture, leading to seemingly unremitting rainfall (SN: 9/13/18). And they may move more slowly, allowing more time to dump that rain on coastal communities. All of this increases the potential hazard on land (SN: 6/6/18).

Once a storm hits land, its energy begins to dissipate. But that relief is coming later than it once did, report physicists Lin Li and Pinaki Chakraborty, both of the Okinawa Institute of Science and Technology in Japan.

Li and Chakraborty analyzed the intensity of historical Atlantic hurricanes over the first 24 hours after landfall. In 1967, a typical storm’s intensity decayed by 76 percent within the first day after landfall. But by 2018, storms were only 52 percent less intense after 24 hours. That trend, the researchers say, aligns with increasing sea-surface temperatures in the Gulf of Mexico and the western Caribbean Sea.

That’s because the intense winds of cyclones feed on moisture and heat picked up from the warm waters, and warmer air can also hold more moisture. So as the oceans heat up, they not only add more moisture, making hurricanes rainier, but also add more heat — like a portable engine the storm uses to fuel its fury for just a bit longer.