什么是“炸弹旋风”？

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When it comes to weather, it is hard to sound more frightening than to call a storm a "bomb cyclone."

But that is how weather experts are describing a huge winter storm that is hitting the U.S. East Coast this week.

From the northern state of Maine to Georgia in the south, the storm has brought high winds and heavy snow. Schools and government offices have closed because of the weather and thousands of flights have been cancelled.

But as fearsome as the storm is, it probably will not be as "explosive" as the name sounds.

Weather experts, or meteorologists, have used the term "bomb" for storms for many years. The word has a clear definition for weather experts, says University of Oklahoma meteorology professor Jason Furtado.

After "bomb cyclone" appeared in a Washington Post story this week, the weather term became popular, or "blew up," on social media. It became a top trending topic. The same thing happened four years ago with the phrase "polar vortex" -- another long-used weather term that was not well known to the public.

The technical term is "Bombogenesis." Bomb cyclone is a shorter way of saying it, which is better for social media, says meteorologist Ryan Maue. He helped popularize "polar vortex" in 2014.

Although "bomb cyclone" sounds bad, Maue notes, nothing will actually explode.

Storm strength is measured by central pressure. The lower the pressure, the stronger it is. A storm is considered a "bomb" when the pressure drops quickly -- at least 24 mililbars in 24 hours.

This week's storm in the United States is expected to strengthen at two times that rate, says Bob Oravec. He is the lead forecaster at the National Weather Service's Weather Prediction Center.

Around the world, about 40 to 50 bomb cyclones develop each year. However, most are over the open ocean and few people notice them.

"We use the term bomb," Furtado said. "We (weather experts) know what it means, but I do think it gets a little hyped up."

I'm Mario Ritter.

Ashley Thompson adapted this AP story for VOA Learning English. Mario Ritter was the editor.