A ‘bomb cyclone’ has hit the US — what is this weather phenomenon?

As a powerful storm slams the central U.S. on Wednesday, people have started calling it a “bomb cyclone.” Are they right?

Yes. The storm has officially undergone bombogenesis, the National Weather Service reported Wednesday, which means it can be called a bomb cyclone.

Bombogenesis occurs when a storm’s barometric pressure drops by 24 millibars – a millibar is a way of measuring pressure – in 24 hours. According to CNN meteorologist Brandon Miller, the storm pressure has “dropped 24 millibars in the last 18 hours. So it more than meets the criteria.”

The lower the pressure, the more powerful the storm. Another meteorologist, the Weather Channel’s Jen Carfagno, also agreed that the storm had “bombed out” Wednesday morning.

A bomb cyclone is basically a winter hurricane, and this storm has a pressure that’s equivalent to a Category 2 hurricane.

Already Wednesday, the storm has produced a 78-mph wind gust in Dallas and set an unofficial record for lowest pressure ever measured in Pueblo, Colorado, at 975 millibars.

“Bombogenesis” is a combination of cyclogenesis, which describes the formation of a cyclone or storm, and bomb, which is, well, pretty self-explanatory.

“This can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters,” the National Oceanic and Atmospheric Administration said.

“The formation of this rapidly strengthening weather system is a process called bombogenesis, which creates what is known as a bomb cyclone.”

In the 1940s, some meteorologists began informally calling some big coastal storms “bombs” because they develop “with a ferocity we rarely, if ever, see over land,” said Fred Sanders, a retired MIT professor, who brought the term into common usage by describing such storms in a 1980 article in the journal Monthly Weather Review.

Many nor’easters — infamous big storms that wallop the East Coast — are the product of bombs, according to meteorologist Jeff Haby.

Jacy Marmaduke and Doyle Rice, USA Today Network

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