Scientists Warn 'Bomb Cyclone' Brings Strong Winds, Cold Temperatures

Jan 3, 2018
Originally published on January 4, 2018 8:58 am

The Eastern United States is being hit by a really powerful winter storm that scientists are calling a bomb cyclone. And yes, that is a scientific term.

The National Weather Service forecasts that the storm, which has struck Florida and the Carolinas, will move northward along the Eastern Seaboard on Thursday and Friday. It will bring snow, ice, strong winds, massive storm surges and plummeting temperatures all the way up to Maine.

Here is what created this monster winter storm.

First, the jet stream brought cold, dry air from Canada southward this past week, casting an unusually cold spell on the entire Eastern United States. That mass of cold air eventually collided with relatively warm, moist air off the Southeastern coast, giving birth to this winter storm.

"Very warm air coming next to cold air mass creates a lot of energy," says Jeffrey B. Halverson, a climatologist at the University of Maryland, Baltimore County.

It also creates a dramatic decline in air pressure, he says. "The pressure is going to drop very, very rapidly."

That's where the word "bomb" comes in, says Jeff Weber, a climatologist at the University Corporation for Atmospheric Research. "We call storms that drop 24 millibars in 24 hours a bomb, a bombogenesis, the beginning of a cyclone."

The more technical (and less eye-catching) term is a baroclinic midlatitude cyclone. This particular one has similarities to Superstorm Sandy, which hit the Eastern United States in 2012.

Unlike this winter storm, Sandy began as a full-fledged hurricane. "As it moved north, it interacted with cold air and transitioned into a baroclinic midlatitude cyclone," Weber says. "And that happened literally as the eye was getting ready to make landfall."

Sandy was more powerful than this new storm, because it had more time to build up energy as it moved north from the Caribbean, he says.

Nevertheless, this storm is expected to be very powerful. Scientists are forecasting that the air pressure in the storm will drop by "about 50 millibars over the next 24 hours," says Weber. "So this will be a big deepening and strong intensification of the storm over the next 24 hours."

"This storm is a big, big wind-making machine," says Halverson. "This is going to cause a lot of problems."

The National Weather Service predicts between 6 and 12 inches of snowfall between Virginia Beach and Boston. Northern New England could get more than 12-18 inches. Eastern Long Island and northern New England are likely to see blizzard conditions.

There will also be coastal flooding and storm surges that can destroy coastal properties and cause beach erosion, especially up along the New England coastline, says Halverson.

Massachusetts and Maine are likely to see widespread power outages caused by gusty winds.

But the storm's impacts won't end there.

"This storm is going to pull down a huge amount of arctic air," says Halverson. "On Friday and Saturday, temperatures are going to be in the gutter."

Temperatures could drop down to single digits, or even below zero. "And if you're going to be out of power, you're really going to be in trouble."

States such as Massachusetts and Maine should prepare shelters for people, he says. "Sheltering for warmth is going to be key, for potentially several days."

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The winter storm hitting the East Coast today is part of a pattern of weather over a number of days. It had a prologue, and it's going to have an epilogue, too. So let's talk it all through in sequence. What comes before a bomb cyclone - the storm itself - and what comes after for much of the country? NPR's science reporter Rhitu Chatterjee has been tracking the storm. She's in our studios. Good morning.

RHITU CHATTERJEE, BYLINE: Good morning, Steve.

INSKEEP: OK, so what was the preliminary to all of this?

CHATTERJEE: So the extremely cold temperatures that much of the U.S., especially eastern part of the country, has been experiencing over the past 10 days was one of the key ingredients for this storm. These cold temperatures were caused by really cold air, what scientists call jet streams, coming down from up north into most of the country. And when that air moved further south and met warm, moist air over the Atlantic, it caused a dramatic drop in air pressure, which is what scientists called a bomb cyclone.

INSKEEP: OK, so this cold air that my mom felt in Indiana, single digits, or in upstate New York or here in Washington D.C. where it was in the teens, that is one of the ingredients of this bomb cyclone.

CHATTERJEE: One of the key ingredients, yeah.

INSKEEP: Hits some warmer air coming up from the Caribbean or wherever. And what is a bomb cyclone as opposed to any other storm?

CHATTERJEE: Well, that's just a scientific term that describes this kind of cyclone that's formed by these two masses of warm and cold air. When they collide, it causes a very, very rapid drop in air pressure, and that's what they call bomb or bombogenesis. It's just a fancy term to describe this dramatic drop in air pressure in a very powerful storm that is going to intensify as it moves north on the - along the East Coast.

INSKEEP: What kind of effects could we see?

CHATTERJEE: So as we know, parts of the southern U.S. have already gotten snow - parts of the U.S. that don't usually get snow.


CHATTERJEE: But New England is really the region that's going to be really badly affected because the storm is going to intensify as it goes north. There are going to be very powerful winds, snow, 12 to 18 inches or more. There could be power outages. And people should be thinking about where they could stay warm if they lose power.

INSKEEP: So what's the epilogue, then, to this bomb cyclone?

CHATTERJEE: Well, this storm is going to subside by tomorrow. But what it's going to do is it's going to pull in more of that cold, frigid Arctic air over most of the country. So both on the East Coast, the Northeast and big chunks of the middle of the United States, the Great Lakes region, are going to see very, very frigid temperatures.

INSKEEP: Wait a minute. This super low pressure area, is it kind of like a black hole? It's going to suck air in its direction.

CHATTERJEE: Exactly, exactly.

INSKEEP: And it's going to be Canadian air, really cold air.

CHATTERJEE: Yeah, for many days to come.

INSKEEP: Meaning if I live in the Great Lakes or anywhere else, I'm going to be feeling the effects of this.

CHATTERJEE: Yes. Most of the middle of the country and east of that.

INSKEEP: Hundreds of miles from the coast. So I have to ask, as we do any time there's an extreme weather event like this or something we haven't really heard of, and I think most people hadn't heard of a bomb cyclone before, although I'm sure...

CHATTERJEE: It's pretty common actually.

INSKEEP: ...Meteorologists have. Is climate change any kind of a factor here?

CHATTERJEE: So, you know, scientists have a much better idea of climate change's connection - influence on hurricanes, but with these kinds of winter storms, they really don't know. The models aren't there quite yet, and they don't know whether there is a connection here.

INSKEEP: Well, listen, try to stay warm today, OK?

CHATTERJEE: You too, Steve, thank you.

INSKEEP: That's NPR's Rhitu Chatterjee.