Hurricanes intensify more rapidly now than they did 30 years ago due largely to a natural climate phenomenon, according to a new study.
Hurricanes that intensify rapidly – a characteristic of almost all powerful hurricanes – do so more strongly and quickly now than they did 30 years ago.
According to the new study published by scientists at the U.S. Department of Energy’s Pacific Northwest National Laboratory and the National Oceanic and Atmospheric Administration, the chief driver is a natural phenomenon that affects the temperature of the waters in the Atlantic.
The climate cycle known as the Atlantic Multidecadal Oscillation (AMO) is central to the increasing intensification of hurricanes, as it broadly affects conditions like sea temperature that are known to influence hurricanes, explained a statement.
Crucially, the AMO governs how the temperature of the water cycles between warmer and cooler. Factors at play when a hurricane gains more power rapidly include the temperature of the surface of the ocean, humidity and the heat content in the ocean.
“This was a surprise, that the AMO seems to be a bigger influence in rapid intensification than other factors, including overall warming,” said Balaguru, the first author of the paper.
Last year’s lineup of powerful storms, including Harvey, Irma, Jose and Maria, encouraged the scientists to analyze the rapid intensification process, which occurs when the maximum wind speed in a hurricane goes up by at least 25 knots within a 24-hour period.
Consistent with other studies, the scientists did not find that rapid intensification is happening more often nowadays. The increase was instead in the strength of fast-growing storms.
The team found that the average boost in wind speed during a 24-hour intensification event is about 13 mph more than it was 30 years ago.
Balaguru added that teasing out the effects of the AMO from broader effects of global warming was beyond the scope of the current study but is a focus for scientists.
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