Your Word of the Week: Bombogenesis | Vol. 4 / No. 20.1

A Nor’easter back in March 2014 | Photo: NOAA, CC0

Hey you lovely people you — especially those of you in the US northeast. You, like me, are getting dumped on with snow this week, but are you going to experience “bombogenesis”? Turns out: not directly, no (but maybe its effects).


“Bombogenesis”—otherwise known as “explosive development” or (as in the case of the wikipedia page) “explosive cyclogenesis“—is a term used to describe when a storm gets worse fast. But there are specifics.

First, it has to be a storm outside the tropics (otherwise it’s known as “rapid deepening” and is a part of the life-cycle of a hurricane or typhoon).

Second, it has to get worse at a specific rate. Now, this might take a little explaining.

See, meteorologists can’t just say “Oh ya, that Nor’easter’s wicked strawng! She’s a real beaut!” and leave it at that. They have science to do. One of the things that helps measure the strength of a storm is the barometric pressure at its center, in part because the faster the winds are circling, the lower the pressure will be in the center. To qualify as “bombogenesis,” a low pressure system must drop 24 millibars within a 24 hour period, averaging 1 millibar an hour.

A millibar is a non-SI unit of atmospheric pressure that’s pretty commonly used by meteorologists. One “atmosphere” (atm), or the pressure at sea level, is 1.01325 bar or 1013.25 millibar—that’s the standard definition, not some kind of hard reality. In reality, pressure goes up and down at sea level (as elsewhere).

According to Ari Sarsalari at, this week’s storm (Stella) is going to go from 1012 millibar at 11pm Monday to 983 millibar on Tuesday at 11pm (which will have the storm’s peak essentially over Boston… yay), a drop that qualifies as bombogenesis.

It’s also important to remember that some of the more colloquial words for it—”a weather bomb” or “a meteorological bomb”—are often used to describe the storm, when the term itself refers to a process that storms undergo. So while you and I won’t be experiencing bombogenesis, the storm we’re going to experience likely will.

So I guess go get your milk and bread while you can, New England.


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Richard Ford Burley is a human, writer, and doctoral candidate at Boston College, as well as Deputy Managing Editor at Ledger, the first academic journal devoted to Bitcoin and other cryptocurrencies. In his spare time he writes about science, skepticism, feminism, and futurism here at This Week In Tomorrow.