What’s a ‘Bomb Cyclone’?—and What to Know About the East Coast’s Potentially History-Making Snowstorm

A major blizzard has brought lashing winds and heavy snowfall across the East Coast, causing many local leaders to declare states of emergency and restrict or limit travel in light of the storm’s “potentially historic” nature.

Early Monday, CNN Weather and FOX Weather reported the storm intensified into a “bomb cyclone,” a term meteorologists use to describe a rapidly intensifying cyclone, which is a large air mass that rotates around a low pressure area or eye of the storm.

But even before its intensification, forecasters already warned about the winter storm’s potentially devastating impact. Cody Snell, a meteorologist at the National Weather Service’s Weather Prediction Center, told the Associated Press that while the U.S. is no stranger to nor'easters—storms along North America’s East Coast—with heavy snowfall and widespread impact, “it’s been several years since we saw one of this magnitude across this large of a region in this very populated part of the country.” 

More than 65 million people, or almost a fifth of the U.S. population, were covered by alerts relating to the storm on Sunday evening, the Washington Post reported, with about 35 million, or more than 10% of the U.S. population, from Virginia to Maine, issued blizzard warnings.  And though some of the warnings had been lifted by Monday afternoon, the impacts of the storm were still being felt across the region, with power outages impacting more than half a million people, historic snowfall impeding road travel, and thousands of flights suffering disruptions. 

‘Bombing out’

Meteorologists declared that the storm had “bombed out” in the early hours of Monday morning.

The winter storm intensified in a process called “bombogenesis,” where a cyclone drops atmospheric pressure in 24 hours, eventually resulting in stronger winds and heavier precipitation—in this case, snow. Bomb cyclones can happen anytime, but they mainly occur during fall and winter when cold air from the Arctic goes down and clashes with warmer air.

But what constitutes “bombogenesis” varies by latitude. According to the National Oceanic and Atmospheric Administration, at the latitude of New York City, the required pressure drop is about 17.8 millibars.

With heavy snowfall and lashing winds, the storm also felled trees and downed power lines. According to poweroutage.us data as of 6 p.m E.T. Monday, more than 500,000 Americans don’t have power, most of whom are in Massachusetts and New Jersey.

In addition to knocking out power lines, high-speed winds like those brought by the storm, which topped 70 miles per hour in some parts of Massachusetts, create low visibility conditions, making it difficult for electric and gas companies to restore power to customers.

The show cannot go on

State officials across the East Coast declared states of emergency in response to the threat. 

In New Jersey, Gov. Mikie Sherrill said Sunday that the late February storm was likely to be the “worst” the state has seen since the Blizzard of 1996, the last time when all 21 counties in the state were issued blizzard warnings. A snowfall total of 27.1 inches was recorded at Newark International Airport as of Monday afternoon, falling less than an inch short of the all-time record 27.8 inches seen in that 1996 blizzard.

New York Gov. Kathy Hochul said in a press conference on Saturday that the National Weather Service issued its first blizzard warning for New York City since 2017—and the first for Long Island since 2022. Hochul warned residents of Long Island on Saturday, a day before snowfall began, that the storm could be “historic” and that the “vulnerability is great,” warning them of possible flooding and urging them to prepare for a “very dangerous situation.” 

New York City Mayor Zohran Mamdani, who issued a local state of emergency, said in a press conference on Sunday that New York City has “not faced a storm of this scale in the last decade” and added that, if the storm unfolds as predicted, with snowfall possibly reaching up to 2 feet, the storm will rank among the top 10 snowfall events the city has ever faced. His prediction had come true by early Monday afternoon, with snowfall in Central Park reaching the ninth highest total on record at nearly 20 inches.

While the city is no stranger to heavy snowfall events—an immense snowstorm in January, for instance, dumped 11 in. of snow in Central Park—the projected snowfall for New York City for this February storm could compete with previous records. Twenty years ago, in February 2006, a snowstorm covered New York City with 26.9 in. of snow. And 10 years ago, in January 2016, a winter storm buried Central Park under 27.5 in. of snow, making it the heaviest snowstorm since record-keeping began in 1869.

Because of the downpour and related travel restrictions, much of the city ground to a standstill, with even Broadway cancelling all shows Sunday evening.

It had begun to come back into motion by the following afternoon, however, as Mamdani lifted a travel ban put into effect Sunday night and announced that public schools would be allowed to hold in-person instruction on Tuesday—though he still urged New Yorkers to stay off the roads and stay indoors.