Warmer oceans could produce more powerful, destructive superstorms

Each of the other three hurricanes followed a surprising and even more destructive course. In these simulations, the hurricane grew so strong that it followed a different track and didn’t collide with the mid-latitude storm. Instead, the hurricane went farther east into the open ocean before turning westward. Next, the hurricane and the mid-latitude storm rotated counterclockwise around their combined center of mass—a phenomenon known as the Fujiwhara effect. As the mid-latitude storm rotated east, the Sandy-like storm gained strength from the Fujiwhara effect and swung westward, making landfall between Maine and Nova Scotia.

“These events are somewhat rare in occurrence, but they do exist in nature,” Lau said. “While they’re turning about each other, they interact. One just took the energy from the other.”

As a result, the three Fujiwhara-enhanced hurricanes’ destructive power peaked at 100 to 160 percent higher than Sandy, and brought as much as 180 percent more rain. And while they made landfall farther north, Lau said, their impacts could be farther-reaching and more devastating than Sandy.

“Because the size of the storm is so large, it could affect the entire Atlantic coast, not just where it makes landfall,” he predicted. “The rainfall itself is probably way out in the ocean, but the storm surge would be catastrophic.”

Lau said the usual approach to simulating a storm in a warmer climate would be to impose a prescribed sea surface temperature, and then adjust the atmospheric conditions such as air temperature, moisture and winds.  The model would then be run many times, making adjustments each time in hopes of creating a Sandy-like storm. But this approach is tedious and does not guarantee meaningful results, Lau explained.

“When confronted with the question whether or not global warming contributed to Sandy, many scientists would just throw their hands up and say, ‘We cannot address the question of how hurricanes will behave in a future climate because the myriad factors affecting storm behaviors are too complex and impossible to simulate’,” Lau said. “This is the first time it was done by using known atmospheric initial conditions that gave rise to Sandy, and simply changing one important variable—in this case, the ocean temperature.”

UMD notes that by using this approach, Lau and colleagues created an informative — if only plausible — scenario that could help to understand how storms might behave in a future warmer climate.   

Lau noted that Sandy was most likely a “perfect storm” brought about by a series of improbable coincidences. As such, it’s hard to make any definite conclusions about whether and how global warming contributed to Sandy and other recent destructive storms, he said.

“However, studies like ours can help provide informative answers to the more tractable question of how a perfect storm like Sandy would behave under warmer ocean temperatures,” Lau said. “It’s a very important line of investigation for better understanding the future of our planet.”

— Read more in William Lau et al., “What would happen to Superstorm Sandy under the influence of a substantially warmer Atlantic Ocean?” Geophysical Research Letters (19 January 2016)