What Exactly Is A Bomb Cyclone And Why It Is So Powerful?

A Bomb Cyclone Explained

You may hear the term "bomb cyclone" and think it's a scary term that meteorologists made up to get your attention. But it's actually rooted in meteorology, from the term "bombogenesis."

Hearing "bomb cyclone" should get your attention, because it describes a storm that is intensifying quickly and one that could bring blinding snow and damaging winds.

We will break it down for you, so the next time you hear that a bomb cyclone is forming, you'll know what to expect.

What Is A Bomb Cyclone?

The term "bomb cyclone," or the meteorological term "bombogenesis," refers to the central pressure of a low-pressure system dropping at least 24 millibars within 24 hours.

Think of rapid intensification when we talk about hurricanes. Bombogenesis is a similar phenomenon: a storm rapidly strengthening. This can bring significant impacts to communities compared to much weaker storms.

However, there is on caveat to the 24 millibars in 24 hours criteria. The requirements vary depending on latitudes.

For example, at 60 degrees latitude, the requirement is 24 millibars in 24 hours. Around 40 degrees latitude (which would include New York City), a storm only has to intensify by 17.8 millibars in 24 hours, according to NOAA.

This is because the Coriolis force is stronger at higher latitudes, and the pressure gradient is naturally stronger. This allows for storms to strengthen more rapidly.

How Common Are They?

A 2021 study led by Robert Fritzen from Northern Illinois University found about 7% of all nontropical low-pressure systems near North America from 1979 to 2019 were bomb cyclones. That's an average of about 18 bomb cyclones per year near North America in that 40-year period.

Most Common In The East

Most bomb cyclones happen off the East Coast, which typically sees about one of these intense storms each year. In the Northeast, they form when there’s a sharp temperature contrast usually between a cold continental air mass meeting the warmer waters of the Atlantic Ocean.

This temperature difference, combined with a strong jet-stream disturbance that forces air upward, sets the stage for bombogenesis. Many nor’easters actually fall into this category, as cold air from Canada collides with the warm Gulf Stream, creating a perfect recipe for explosive storm growth.

When Do Bomb Cyclones Most Often Occur?

While bomb cyclones can happen any time of year, they are most common during the months of October through March.

This, again, is because of the sharp temperature contrast in the colder months, helping to fuel the explosive storms.

What Impacts Can Bomb Cyclones Bring?

Winds and precipitation (including snowfall) can be rather intense. Blizzard conditions can occur, sometimes accompanied by lightning as the system intensifies.

It's not uncommon for wind gusts to top 50 mph, which can down trees, knock out power and push water ashore, leading to coastal and lakeshore flooding.

Looking Back At More Notable Bomb Cyclones

-Early January 2018: Winter Storm Grayson intensified at the most rapid rate on record for the western Atlantic Ocean. The storm plunged an astonishing 59 millibars in 24 hours to a low of 950 millibars. That's roughly the equivalent of a Category 3 hurricane.

-In February 2013: Winter Storm Nemo dropped 29 millibars within a span of 24 hours. A barometric pressure of 1,000 millibars was recorded at 4 a.m. on Feb. 8, and dropped to 971 millibars by 4 a.m. the following day. This powerful low-pressure system brought a wind gust of 83 mph near Cuttyhunk, Massachusetts, and thundersnow was reported on Long Island.

-An example of bombogenesis over land was the "Octobomb" that impacted portions of the Plains and Midwest Oct. 25-27, 2010. All-time record-low barometric pressure readings were set by this system in Minnesota and Wisconsin.

How To Prepare For A Bomb Cyclone

If you hear meteorologists warn of a bomb cyclone, and you know the storm is headed your way, you would prepare just like any other storm.

Make sure you have fresh batteries and all the essentials like food and water, in case you lose power. Make sure to bring inside any loose items that might get blown around in strong winds. Have a way to get weather alerts, even in the event that power is lost. And check the forecast frequently, because changes to the forecast can happen.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.