In weather forecasts, the term “bomb cyclone” can show up when meteorologists expect a storm to intensify unusually fast. The National Oceanic and Atmospheric Administration describes the process as bombogenesis, with a key benchmark: a storm’s central pressure must fall by at least 24 millibars within 24 hours. Because central pressure is used to gauge storm intensity, NOAA’s definition links a fast pressure drop to a rapidly strengthening system.
That rapid intensification can matter for what people experience on the ground. AP reports that storms meeting the bombogenesis criteria can bring heavy rain, blizzard conditions and intense winds, and those conditions can translate into practical hazards such as downed trees and power outages.
Andrew Orrison, a meteorologist with the National Weather Service in College Park, Maryland, said that when viewers hear “bomb cyclone” on a nightly forecast, it typically reflects broad activity across the storm system. “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,” Orrison said.
Orrison also pointed to the atmospheric setup that helps drive bomb cyclones. “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,” Orrison said, describing how contrasting air masses support the formation and development of the low-pressure centers that then deepen quickly.
Bomb cyclones are possible in any season, but they occur mainly during fall and winter, when very cold Arctic air can push south and collide with warmer air masses. Regions in North America prone to seeing bomb cyclones include Alaska, the Pacific Northwest and the Great Lakes region.