Meteorologist explains what a 'bomb cyclone' is, and what it means for Connecticut

It's not a winter hurricane. It's also not a bomb. It's also not out of the ordinary.

But that didn't stop storm-watchers across Connecticut from embracing the term "bomb cyclone" to describe Thursday's storm as high winds and snow closed schools, kept drivers at home and utility crews on edge

A bomb cyclone is the abbreviated name for when a surface cyclone undergoes "bombogenesis," meaning the atmospheric pressure in the storm drops rapidly due to hot and cold temperatures colliding. According to the National Oceanic and Atmospheric Administration's glossary of weather terms, a cyclone is a closed storm system that rotates counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

For "bombogenesis" to occur, the pressure in the storm must drop 24 millibars in 24 hours, which can cause high winds, lightning and thunder. A millibar is the unit that meteorologists use to measure pressure in the atmosphere; as the pressure plummets, the lines illustrating the storm on a weather map get closer together and conditions intensify.

"It's like an explosion, it happens very fast," said Gary Lessor, a meteorologist and assistant director with The Weather Center at Western Connecticut State University in Danbury. "You can see the storm system turning and intensifying very quickly, and it kind of resembles a bomb."

"As it's strengthening so fast, that's where you're getting the thunder and lightning," he said.

In an article published online Wednesday, Huffington Post attributed the invention of the term to McGill University meteorology professor John Gyakum and Massachusetts Institute of Technology meteorologist Fred Sanders, who first used it in a 1980 paper.

Gyakum told HuffPost he doesn't use the term anymore.

"When I talk about these explosively developing storms, I go through the trouble of mouthing the terms 'explosively developing,' and I don't use 'bomb,'" he said to HuffPost. "It's somewhat inappropriate when you consider other aspects of the world right now."

Lessor said names like "bomb cyclone" have taken off as amateur and professional storm-watchers have clamored for easy ways to describe meteorological phenomena.

"Meteorology has taken a lot of liberties in the past 20 years," Lessor said. "Things are a lot looser — it makes it easier for people to understand."

Severe storms like the blizzard that hit the East Coast on Thursday are common in the Atlantic Ocean, but make the most headlines when they hit the coast and keep going, Lessor said.

"It's nothing unusual," he said. "You get several of these storms every winter."

By 10 a.m., the storm was generating top wind speeds of 50 miles per hour at the U.S. Coast Guard Academy in New London, 47 mph at Groton-New London Airport and 45 mph in Ledyard.

Despite the hurricane-force winds, Thursday's storm wasn't technically a hurricane, Lessor said.

"You have the winds that are verified of hurricane force on Cape Cod," he said. "But it's not really a hurricane."

Thursday afternoon the National Weather Service reported that between 8 and 10.5 inches of snow had fallen in New London County, and the snow would keep falling into Thursday evening, Lessor said.

By 3 p.m., 8 inches had fallen in Stonington and 8.5 inches had fallen in both Gales Ferry and Norwich, according to snow spotters reporting to the National Weather Service.

Temperatures would only continue to drop from a Thursday afternoon temperature of 28 degrees in Groton, down to a high of 20 degrees Friday and low temperatures dipping below zero on Friday and Saturday night.

"This is warm," Lessor said. "Enjoy the warmth today."


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