Skip to main content

How bomb cyclones form and create dangerous conditions

When turbulent weather with whipping winds and heavy snow is in the forecast, meteorologists sometimes warn that a storm could “bomb out” or become a bomb cyclone. But what exactly does this mean?

According to the U.S. National Oceanic and Atmospheric Administration, certain storms undergo bombogenesis, which happens when a storm’s central pressure drops at least 24 millibars in 24 hours. These storms are sometimes called bomb cyclones. Storm intensity is measured by central pressure, so the lower the pressure, the stronger the storm.

Such rapidly strengthening storms are capable of producing heavy rain, blizzard conditions and intense winds that can create dangerous conditions such as downed trees and power outages.

“If you’re watching TV at night and the weather report comes on and you’re hearing ‘bomb cyclone’ being used, that usually means there’s quite a bit of active weather going on,” said Andrew Orrison, a meteorologist with the National Weather Service in College Park, Maryland.

Bomb cyclones can happen in any season, but mainly occur during fall and winter when frigid air from the Arctic can creep south and clash with warmer air masses.

“It’s really the clash of those air masses that really kind of helps to generate the areas of low pressure in the first place,” said Orrison.

Regions in North America that are prone to seeing bomb cyclones include Alaska, the Pacific Northwest and the Great Lakes region.

“It’s not common to get bomb cyclones at lower latitudes. So generally speaking, you wouldn’t see a bomb cyclone across, let’s say, the southern United States,” said Orrison.

___

The Associated Press’ climate and environmental coverage receives financial support from multiple private foundations. AP is solely responsible for all content. Find AP’s standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org.

Grandfather recovering from surgery after bison attack at Yellowstone sent him flying

(CNN) — What started as a yearly trip for a grandfather and his grandson turned into a visit to a Montana hospital after a bison attack at Yellowstone National Park.Carl McDaniel, 65, was hospitalized with a broken femur after a bison charged and tossed him into the air Friday evening at the park’s Bridge Bay Campground, according to McDaniel and the National Park Service.He was visiting the park with his 13-year-old grandson when they decided to take a walk after dinner.Along the way, they encountered a large bison that appeared to be rolling around in the dust and was not bothering anyone, McDaniel told CNN.“We were about a hundred yards away,” McDaniel said. “He was not aggressive; he was not having problems and we took some pictures and decided to walk on.”McDaniel and his grandson snapped a quick photo and continued with their walk, video of the encounter shows. At the same time, a truck drove by, and the driver laid on his horn in what appeared to be an attempt to get the bison to move, McDaniel said. There is no audio on the video.The bison then appeared to become agitated and began running toward the pair.“There was little time to decide what to do. At that point, he was within 100 yards; he could be to us in seconds, so I told my grandson to run in one direction and I went the other to try and draw him away,” McDaniel said.The animal then pushed McDaniel with the top of its head, sending him flying into the air before he hit the ground, the grandfather said.“When I was on the ground immobile, unable to move, he was right on top of me. He could have stomped on me, he could have gored me, he could have done almost anything to take my life, and he did not do so,” McDaniel said.After McDaniel hit the ground, photographer Mike MacLeod, who captured the encounter on video, had to step in, he told Cowboy State Daily.“I was really afraid he was going to gore the guy on the ground, so I stopped videotaping and ran at the bison, yelled loud, and was trying to be as big and intimidating as possible,” MacLeod said.After the bison took off, people rushed over to McDaniel, who was in a lot of pain, MacLeod told Cowboy State Daily. Yellowstone EMS arrived soon after, he said.“Park emergency medical personnel responded and transported him to a nearby hospital,” the National Park Service said in confirming the incident in a statement to CNN.This is the second bison attack at Yellowstone this year. A 12-year-old was injured near Mud Volcano on June 26, according to the agency.After Friday’s attack, “all the people that were there were amazing; they were all positive, they were trying to help as best they could,” McDaniel said. A nurse started tending to his leg, while another bystander held his head.He was then transferred to a hospital in Bozeman, a two-hour journey during which he was in intense pain. He said he was grateful for the paramedic who helped him along the way.McDaniel broke his femur, the body’s strongest bone, in four places near his hip and suffered several bruises. He had surgery Sunday and could stand by Monday.“I will be doing physical therapy for the next few days to get to walk, but it was not as catastrophic as it could have been,” McDaniel said.The National Park Service advises visitors to stay at least 25 yards away from bison at all times and to never approach the animals. “If the bison follows you, spray bear spray as you are moving away, and seek cover behind nearby trees or cars,” the agency said.Correction: An earlier version of this story understated how far visitors should stay away from bison. The National Park Service advises visitors to stay at least 25 yards from them.The-CNN-Wire™ & © 2026 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.
Read Next Story