Blizzard-like ‘bomb cyclones’ get boost from warming oceans

The warming of ocean waters through climate change creates ideal conditions for more “bomb cyclone” events like the one that battered the Northeast with extreme winter weather in late January, experts say.

The storm brought 23.6 inches of snow to the Boston area, tying its single-day snowfall record, and led to at least four deaths on Long Island, N.Y. Across Massachusetts, nearly 9,000 customers were left without power for the remainder of the weekend. 

A bomb cyclone, also known as explosive cyclogenesis, is formed by air close to the surface of the planet rising rapidly, causing barometric pressure to plunge. The lower pressure is usually directly proportional to the storm’s intensity.

Climatologists say that while it’s unclear whether climate change is leading to more storms and hurricanes, it likely correlates with more intense storms. Barry Keim, a climatologist at the University of Louisiana who also serves as the state climatologist, said there is likely a similar dynamic with bomb cyclones.

“It’s sort of like rapid intensification of a hurricane. It’s the same basic kind of phenomenon, except we’re not dealing with hurricanes. In this case, we’re not dealing with tropical cyclones, but we’re dealing with what we call extra-tropical cyclones,” Keim told The Hill.

The direct relationship between climate change and explosive cyclogenesis merits further study, Keim said, but by definition increasing ocean temperatures heighten conditions for more intense bomb cyclones.

“By and large … the oceans are getting warmer,” Keim said, adding warming surface temperatures can fuel bomb cyclones in the form of the “Arctic intrusion of air spilling out of Canada across the eastern United States, and [you] have that gradually drift off to East Coast” where it “start[s] interacting with this incredibly warm moist air.” 

This contrast, he said, is “the perfect setup” for events like last weekend’s bomb cyclone. 

“When you have a warmer ocean it’s perfectly reasonable to think that nor’easters could be more intense,” said Justin Mankin, an assistant professor at Dartmouth College with a focus in climate variability and dynamics.

“That [human] activity that’s created these conditions — where more heat is being sucked up by oceans — provides fuel for these types of weather events,” he said. 

Another factor is water vapor, which can produce wetter storms, noted Tom Di Liberto, a meteorologist and climatologist with the National Oceanic and Atmospheric Administration.

“The warmer the ocean water, that means you can potentially have more water vapor getting into the storm, which leads to these storms potentially being wetter,” he said.

Bomb cyclones’ behavior can be harder to predict because they can generally form in a wider variety of settings than hurricanes.

While hurricanes typically form in warm oceans, bomb cyclones have been known to form inland as well, such as in the case of a 2019 storm that hit the Midwest and Northern Plains.

Keim noted that the most recent storm could easily have been almost entirely over the ocean rather than along coastline if its track had varied slightly.  

Although resilience planning is largely focused on the risks of extreme heat, the impact of the weather that hit the Northeast illustrates the risks that come with a combination of higher sea levels and extreme winter weather.

Indeed, coastal communities in the path of the bomb cyclone, such as Cape Cod, saw not just ice and snow but flooding from waves crashing over seawalls. A 32-foot wave was recorded off Gloucester, Mass., the departure point for a commercial fishing vessel lost in the 1991 “perfect storm.” 

Di Liberto noted that some aspects of the relationship between climate change and bomb cyclone conditions remain a point of contention within the scientific community.

One of those debates, he said, is over whether the warming of the Arctic directly influences “the jet stream across the mid-latitudes where we all live” that could directly affect storms like January’s. 

“Some folks are in the camp that thinks that Arctic warming could have its influence and others say we can’t tell right now and maybe even not,” he said.  

Di Liberto added that while extreme winter weather is frequently and erroneously cited as evidence that warming is not occurring, warming temperatures do not preclude weather events like the bomb cyclone.  

“We still expect there to be rainstorms even in a warming world,” he said. “The question is whether you can get some of this cold air to come down to make temperatures cold enough for snow. So it’s completely normal to experience the occasional snowstorm even in a warming world.”