US winter storm Elliott: what is bomb cyclone, how cold will it be, will it hit UK?

A frigid winter storm has killed at least 57 people as it swept across the US, knocking out power to hundreds of thousands of homes on Christmas Day.

Across the US, officials have attributed deaths to exposure, car crashes, a falling tree branch and other effects of the storm. Around 200 million Americans have been affected by the unprecendented winter storm which has engulfed most of the continent, stretching from the Great Lakes near Canada to the Rio Grande along the border with Mexico.

The deaths were recorded in 12 states: Colorado, Illinois, Kansas, Kentucky, Michigan, Missouri, Nebraska, New York, Ohio, Oklahoma, Tennessee and Wisconsin.

More than 1.5m people are without power, with at least 57 deaths linked to freezing weather. Temperatures have plunged leaving hundreds of thousands of homes and businesses without power and airports across the country have been closed, with some governors putting driving bans in place.

Some 1,346 domestic and international flights were cancelled as of early Sunday, according to the tracking site FlightAware. While many people were trapped inside their homes or cars due to giant snow drifts.

Winter Storm Elliott has become a bomb cyclone, as huge pressure causes temperatures to plummet quickly. It is the equivalent of a Category 2 hurricane. In some parts of the country, they dropped to -45C. The storm unleashed its full fury on Buffalo, New York, with hurricane-force winds causing whiteout conditions. Emergency response efforts were paralysed, and the city’s international airport was shut down.

The US National Weather Service (NWS) has said that this was one of the greatest extents of winter weather warnings and advisories ever. About 60% of the US population faced some sort of winter weather advisory or warning, and temperatures plummeted drastically below normal from east of the Rocky Mountains to the Appalachians, it said.

Blinding blizzards, freezing rain and frigid cold also knocked out power in places from Maine to Seattle, while a major electricity grid operator warned the 65 million people it serves across the eastern US that rolling blackouts might be required.

Here’s everything you need to know about the US winter storm.

What is a ‘bomb cyclone’?

According to weather forecasting service Accuweather, a bomb cyclone or ‘bombogenesis’ is a storm (low pressure area) that undergoes rapid strengthening. The vast majority of such storms occur over the ocean. The storm can be tropical or non-tropical in nature.

The service said: “The term bombogenesis comes from the merging of two words: bomb and cyclogenesis. All storms are cyclones, and genesis means the creation or beginning. In this case, bomb refers to explosive development. Altogether the term means explosive storm strengthening.”

A cyclone is a non-tropical storm or hurricane. It is essentially a giant rising column of air that spins counterclockwise over the Northern Hemisphere. A 2021 study led by Robert Fritzen from Northern Illinois University found about 7% of all nontropical low-pressure systems near North America from 1979 to 2019 were bomb cyclones. That amounted to about 18 bomb cyclones per year, on average, near North America in that 40-year period.

Examples of storms that underwent bombogenesis include the Superstorm of 1993 which was dubbed the storm of the century; Storm Dennis, which impacted the United Kingdom on 14 February, 2020; and the storms that hit the northeastern and western United States in late October 2021.

How cold will it get?

The storm has already delivered heavy snow and ice, making for grim road conditions with poor visibility and leaving some drivers stranded in unbearably frigid temperatures. Travel has been hampered with hundreds of miles of road closures and flight cancellations growing rapidly.

The NWS said temperatures of -50F (-45C) and -70F were possible in some parts of the country. They warned that even in major metro areas frostbite will be a major danger. Lincoln, in west Montana, has already recorded a staggering temperature of -49F (-45C).

In a Twitter post, the agency said that around 60% of the US population are under some form of winter weather warnings or advisories across the country.

Among the warnings, it added that blizzard conditions, potentially damaging winds, extremely dangerous travel and whiteout conditions, life-threatening cold temperatures, and the threat of coastal and inland flooding could be expected.

Have people died in the storm?

It is thought that at least 57 deaths have been linked to the extreme weather, with more deaths expected to come. Across the US, officials have attributed deaths to exposure, car crashes, a falling tree branch and other effects of the storm.

At least three people died in the Buffalo area, including two who suffered medical emergencies in their homes and could not be saved because emergency crews were unable to reach them amid historic blizzard conditions. At least four people died in a massive pile-up involving 50 vehicles on the Ohio Turnpike. A Kansas City driver was killed on Thursday after skidding into a creek, and three others died on Wednesday in separate crashes on icy northern Kansas roads.

A utility worker in Ohio was also killed on Friday (23 December) while trying to restore power, according to the Buckeye Rural Electric Cooperative. It said the 22-year-old died in “an electrical contact incident” near Pedro in Lawrence County.

The medical examiner’s office in New York’s Erie County determined the 27 deaths there to be directly related to the blizzard, County Executive Mark Poloncarz said at a news conference, reported by NBC.

He said many died from heart problems while shoveling or blowing snow. Others were found dead in their cars. At least one person in Niagara County died from carbon monoxide poisoning, he said. At least 18 people died in Buffalo, Mayor Byron Brown said Monday (26 December) afternoon.

Some of those deaths are not included in Erie County’s official tally, Poloncarz said, adding that the county was working to confirm them.

A woman in Vermont died in a hospital on Friday after a tree broke in the high winds and fell on her. Police in Colorado Springs said they found the body of a person who appeared to be homeless as sub-zero temperatures and snow descended on the region.

Near Janesville, Wisconsin, a 57-year-old woman died Friday after falling through the ice on a river, the Rock County Sheriff’s Office announced.