Massive storm moving across central U.S.

This National Weather Service map displays the various warnings and advisories that had been issued as of Tuesday evening. The red indicates a blizzard warning, the dark blue is a winter storm that doesn't quite reach blizzard status and the shades of green warn of potential for flooding. The gray is for dense fog. The brown is a wind warning and the yellow is a tornado watch.

A giant storm moving into Nebraska today is the product of a rare phenomenon called bombogenesis or bomb cyclone.

In essence, it refers to an explosive storm that quickly gathers strength.

Technically speaking, a bomb cyclone is a storm with extraordinarily low pressure, measured by a sharp drop in atmospheric pressure within a 24-hour time span. The result is extreme winds and heavy rain or snowfall.

These violent storms can knock down trees and power lines. They’re fueled by a column of air — similar to the eye of a hurricane — that rushes up into the atmosphere, leaving a void. Surrounding air whooshes in quickly to fill that void, creating wind speeds in excess of 60 mph.

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The storm has already begun to pick up speed. To learn what to expect from this storm and how it forms, we asked AccuWeather senior meteorologist Dave Samuhel to explain.

What is bombogenesis?

Samuhel: It’s basically when the surface pressure of the storm, measured in millibars, drops 24 millibars in 24 hours. Yesterday it was about 1005 millibars, and now it’s 971 millibars, so it has gone well past the criteria.

What changes as that pressure drops?

Samuhel: The winds just increase remarkably; 971 millibars, where this is right now, is equivalent to about a Category 3 hurricane. Of course, the pressure difference is over a much smaller distance in a hurricane — that’s why you get those much more intense winds. But certainly we’re seeing some very high winds across a huge region. It’s gusting over 60 mph in Scottsbluff (Nebraska).

What are the chief concerns with a storm like this?

Samuhel: The wind is probably the big concern, but this storm is also producing a lot of snow on the north side of it. There’s automatic blizzard conditions thanks to these high winds. You have severe weather as well.

How common a phenomenon is bombogenesis?

Samuhel: To this magnitude, not very often. It’s right around the record low pressure levels for Kansas and Colorado. We probably see something like this once a year somewhere in the country.

What should people be doing to brace for this storm?

Samuhel: In western parts of (Nebraska), it’s life-threatening with blizzard conditions and winds up to 60 mph. It’s just a complete whiteout. At least there’s not extreme cold with this storm, but it’s cold enough. With winds this strong, you’re going to have a lot of trees coming down.

How will the storm manifest in different parts of the state?

Samuhel: Fortunately, in Omaha, the effects aren’t going to be as bad as they will be in western parts of the state. That’s more to the west. They’re just going to get crushed out there. Upwards of a foot of snow should easily occur out there. Northwestern Nebraska looks to get as much snowfall as anybody out of this storm. Wind could be as high as 70 before this storm is done.

Some answers have been shortened for length and clarity.

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