What is a 'bomb cyclone'? The science of rapid intensification
The dramatic term describes a storm whose pressure drops explosively, and it is more common than you might think.
The term "bomb cyclone" sounds alarming, and it entered common usage after a series of powerful storms, but it describes a specific and well-understood meteorological phenomenon: a storm that strengthens with explosive speed.
Technically, a "bomb cyclone" results from a process called bombogenesis, which occurs when the central pressure of a storm drops by at least 24 millibars within 24 hours. The lower the pressure at a storm's centre, the stronger the winds it can generate, so a rapid pressure drop signals rapid strengthening.
These storms are most common in the cooler months, when sharp contrasts between cold air masses and warm, moist air — often along the boundary between land and a warm ocean current — provide the energy for explosive development. The eastern United States, where frigid continental air meets the warm Gulf Stream, is a frequent breeding ground.
The result can be a sprawling winter storm packing hurricane-force wind gusts, heavy snow, coastal flooding and blizzard conditions. While the name is dramatic, bombogenesis is a routine part of the atmosphere's behaviour and happens somewhere on Earth dozens of times a year.
Understanding the term helps cut through the hype: a "bomb cyclone" is not a new or mysterious kind of storm, but a measure of how fast a storm is intensifying. For forecasters, spotting the conditions for bombogenesis is key to warning the public before a storm reaches its full, dangerous strength.