“Bomb cyclone” bearing down on central U.S.

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Denver — A powerful winter storm bearing down on the central United States is expected to impact areas from the Central Rockies to the Mississippi Valley and Upper Great Lakes, according to the National Weather Service.

“This storm will be responsible for heavy rains… severe thunderstorms… isolated flooding… heavy snows… blizzard conditions and high winds over the next two days,” the weather service said Wednesday.

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The storm is being called a “bomb cyclone” because the pressure in the center of the storm was expected to drop quickly as it raced toward Colorado.

“I can’t say I’ve seen a storm with such intensity this far west,” said CBS News climate and weather contributor Jeff Berardelli.

What is a “bomb cyclone”?

In the Northern Hemisphere, areas of low pressure are called cyclones, and rapidly developing storms are often called bombs or weather bombs. To qualify as a “bomb cylcone,” an area of low pressure must drop at least 24 millibars in 24 hours or less. Weather models show the center of Wednesday’s low pressure dropping anywhere from 24 to 30 millibars in less than a day as it gains strength over Colorado’s eastern plains, CBS Denver reported.

Other terms you may hear in meteorology when dealing with a storm like this include “explosive,” “cyclogenesis,” or “bombogenesis.” Explosive refers to the rapid growth, and cyclogenesis means you have an area of low pressure that is gaining strength.

“A set of unique factors are all coming together for a rapid drop in pressure,” Berardelli said. “The definition of bombogenesis is a pressure drop of 24 millibars in 24 hours. This will far exceed that.”

Winter storm forecast

The storm was expected to keep intensifying Wednesday in the Central Rockies, push eastward through the Central Plains Wednesday and into the Upper Mississippi Valley and Upper Great Lakes region on Thursday.

“Travel across the region will be difficult, if not impossible,” the National Weather Service said. “Road closures are also possible along with power outages across the plains due to winds gusting from 60 to 80 mph.”

The storm could be historic in terms of the minimum pressure that could be measured in the Colorado region, CBS Denver reported. In other words, the storm is an aberration, which is part of the reason a laundry list of weather watches, warnings and advisories were in place across the state.

Meanwhile, thunderstorms were expected to keep pushing eastward Wednesday from the Southern Plains to the lower to middle Mississippi Valley. “Heavy rains… isolated flooding and severe weather will accompany these thunderstorms as they march fairly quickly eastward,” the weather service said.

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