What Is a Bomb Cyclone?

By: Jesslyn Shields  | 
bomb cyclone
A massive bomb cyclone barreled into the East Coast of the U.S. Jan. 4, 2017. NOAA/CIRA

This planet has a lot of fascinating weather, but the most fascinating weather is the stuff you want to stay far away from. Take a bomb cyclone, for instance: It's basically a rapidly intensifying storm that happens in winter, bringing with it destructive, hurricane-like weather. Although these storms are uncommon and therefore interesting, you don't necessarily want to be on the receiving end of one.


Bomb Cyclones Are Intense Winter Storms

Cyclones are large, rotating storms that happen more often north of the equator of our planet, commonly between the months of June and November along the Eastern Seaboard of the U.S. However, where warmer weather hurricanes can deliver high winds and massive amounts of rain, bomb cyclones can deliver swift, violent storms and even blizzards. The reason for this, and what makes a bomb cyclone unique, is a phenomenon called bombogenesis.


What Is Bombogenesis?

One of the main things that creates weather has to do with what cold and warm air are doing at any particular moment. A bomb cyclone starts as a big storm cruising across the ocean — normally at a higher latitude than a normal hurricane. It's formed by the difference in temperature between the warmer air coming from the Gulf Stream current of the Atlantic Ocean and the colder air coming off the North American continent. When warm, moist air meets cold, dry air, clouds form in the upper atmosphere and start swirling around, creating a low pressure area. As the storm gets bigger it can produce jet streaks, or very strong winds within the jet stream that can overlay the developing low pressure system, which is where the bomb cyclone magic happens.


How Are Pressure Differences Involved?

Because the atmosphere hates pressure differences, these high winds whipping over a low pressure system create something like a hole in a doughnut: Warm air starts to rise rapidly through the center of the storm to even things out, but this causes the pressure at the center of the storm to plummet. Bombogenesis, the calling card of a bomb cyclone, happens when the barometric pressure at the center of the cyclone pressure drops at least 24 millibars in 24 hours (a millibar is a unit of measurement for atmospheric pressure). Some of these storms can intensify much more quickly, though, dropping 60 millibars in 24 hours.

The result, as you can imagine, is impressive. These storms can be as intense as a regular-season hurricane, but even more ferocious as they can drop immense amounts of snow as well as 50 mile per hour (80.5 kilometer per hour) winds, causing flooding, beach erosion, loss of power and storm surges.