What is bombogenesis?

What is bombogenesis?
Satellite view of a massive nor'easter raging off the East Coast of the United States in March 2018.Satellite view of a massive nor’easter raging off the East Coast of the United States in March 2018.

Image: rammb/cira

There are plenty of terms meteorologists use to describe storm systems. From “atmospheric river” to “jet streak,” meteorologists love to label weather phenomena in colorful and sometimes goofy ways. (Here’s looking at you, “vorticity lobe.”)

But perhaps the most exotic-sounding and useful weather term floating around these days is “bombogenesis.” 

While it sounds like a band name or a fancy new video game console, bombogenesis is really just a fancy way of saying that an area of low pressure is rapidly intensifying. 

Specifically, to qualify as a “weather bomb,” the minimum central pressure of a storm must drop by at least 24 millibars within 24 hours. 

Some storms meet or exceed this threshold. 

One of the best examples of this kind of rapid intensification was the “Bomb Cyclone” that hit the East Coast of the  in early January 2018. 

That storm intensified 59 millibars in 24 hours, which was the fastest intensification rate ever observed in a winter storm in that part of the world since at least the mid-1970s, according to data from David Roth, a meteorologist at the Weather Prediction Center, and Andrea Lang, an assistant professor at the University of Albany.

Bombogenesis is a fairly rare occurrence, happening in a particular region in the northern mid-latitudes, such as the Northeast, a few times a season. Such intense, large-scale storms are more common in the U.S. during fall, winter and spring.

Storms that “bomb out” are typically accompanied by strong winds, since air rushes from higher to lower pressure, as well as heavy precipitation. For example, a storm that hit the Mid-Atlantic and Northeast in early March 2018 was undergoing bombogenesis. It knocked out power to hundreds of thousands in the Washington, D.C. area due to strong winds in excess of 60 miles per hour, and also brought hurricane force winds to Cape Cod and the Islands. 

Zoomed-in satellite image of the eye-like feature in the 'bomb cyclone' on Jan. 4, 2018.

Zoomed-in satellite image of the eye-like feature in the ‘bomb cyclone’ on Jan. 4, 2018.

Image: NOAA

The storms that go through this process are fueled by intense air and moisture contrasts, such as the presence of a polar air mass across the northeastern U.S., and a warm and moist air mass sitting over the Gulf Stream waters. 

Aided by jet stream winds and areas of atmospheric spin, these storms can generate a lot of lift, which is a trigger for heavy rain and snow. 

East Coast blizzards tend to be weather bombs, as are some of the more intense North Atlantic and North Pacific winter storms. Such a storm recently caused damage in Newfoundland, where winds exceeded 100 miles per hour. That storm featured a staggering 42 millibar pressure drop in 24 hours, which helps explain the strong winds. 

And in the U.K., winter storm Doris rapidly intensified, too, causing damage as well. 

Because bombogenesis often occurs over the oceans, the National Weather Service’s Ocean Prediction Center maintains one of the best catalogs of weather bomb animations. They reveal how these storms are shape shifters, going from relatively innocuous-looking spins to full-fledged, backwards shaped commas. 

So remember, the next time you hear the word “bombogenesis,” or a storm referred to as a weather “bomb,” it means you should take that storm seriously.

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