This week’s nor’easter met criteria to be considered a ‘bomb cyclone’

Weather Blog

EAST PROVIDENCE, R.I. (WPRI) — A nor’easter that impacted Southern New England Tuesday night into Wednesday and knocked out power to thousands of homes and businesses was what’s known as a “bomb cyclone,” according to the National Weather Service.

You may have heard this term before, but what exactly is a bomb cyclone?

“It’s definitely not a new term. In fact, it’s been discussed as early back as the 40s and 50s, but didn’t get its sort of popularity until about the 1980s,” NWS Taunton Meteorologist Torry Gaucher said.

The term is associated with and derived from other weather phenomena: “bombogenesis” and “cyclogenesis.”

When a storm strengthens or rapidly intensifies, the pressure within it drops. If the pressure within a storm drops at least 24 mb (millibars) within a 24-hour period, it’s considered to be a bomb cyclone.

For this week’s storm, data from Nantucket shows there was a 28 mb drop within 24 hours, going from 1008 mb to 980 mb.

Bomb cyclones are only found with extra-tropical systems, according to the NWS. Tropical systems, even when undergoing rapid intensification, cannot be classified as such.

Late October and early November is the prime time for Southern New England to see some nasty nor’easters. Gaucher said there are signs of a pattern change that presents the threat of more storms.

“We definitely have that clashing, colder air mass that’s starting to sink further south,” he said. “We still have relatively warm ocean temperatures, which these storms like to feed off of. Water temperatures south of New England are still holding onto near 70 degrees.”

The NWS says the last time Southern New England was hit by a bomb cyclone was in 2019.

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