Why Thursday’s storm had so much thundersnow

Photo courtesy Brad Smith

PROVIDENCE, R.I. (WPRI) – The nor’easter of Feb. 9, 2017, may very well be remembered as the “thundersnow” storm.

Communities across Rhode Island – and the rest of New England – experienced loud daytime booms from above as heavy snow was coming down.


T.J. DelSanto hears thundersnow videoRELATED MUST WATCH VIDEO: Thundersnow caught live on air


In several instances, lightning from the storm caused serious damage, including in Warwick where a bolt blew a hole through the side of a home and split a tree in half.

Photo courtesy Brad Smith
Photo courtesy Brad Smith

WPRI 12 meteorologist T.J. Del Santo said in his 20 years forecasting weather in the Ocean State, he’s never experienced so much thundersnow.

“This storm was exceptional,” Del Santo said. “The lightning on the screen looked like a summertime thunderstorm.”

So what is thundersnow?

Del Santo said thundersnow is just like a lightning show in a summer storm: vertical motion in the clouds causes friction and creates an electrical charge through static electricity.

“Lightning forms as the result of collision of particles in the atmosphere,” he said. “In the summertime it’s usually the collision of hailstones colliding with each other and it creates static electricity.”

He said a similar situation can happen during a winter storm.

“In this case it can be a mixture of snowflakes or graupel – which is smaller snowflakes, almost like Styrofoam balls,” Del Santo said. “They are all bumping up against each other with these strong winds that are going up, they are all colliding with each other, and the end result is static electricity.”

Why did we experience so much thundersnow this time?

Bill Simpson, a spokesperson for the National Weather Service in Taunton, said the culprit was how quickly this storm system formed.

Photo courtesy Brad Smith
Photo courtesy Brad Smith

“It developed so fast,” Simpson said. “It was very unstable aloft, meaning the upper atmosphere was moving vertically.”

He said the jet stream above the clouds led to a very unstable upper atmosphere which quickly pushed air upward.

“It’s like opening up your flu in your fireplace and all the air pushes upward,” Simpson said. “The jet stream aloft made it conducive to that kind of rapid unstable air.”

With the air pushing upward, the particles collided and – as in a summertime storm – that friction led to electrical charges.

For it to happen in the winter is “relatively rare but not unusual,” according to Simpson.

Del Santo said lightning in thunderstorms usually stays within the clouds, but they can lead to ground strikes.

“It can cause similar damage and blow up trees or hit a house and cause fires,” Del Santo said. “It’s electricity, so it can do the same damage as summertime storm could.”

He added that winter storms often have a lower cloud cover so it can create something called “inversion.”

“The sound tends to get squashed in the lower atmosphere and spreads out,” he said – meaning the booms can last longer and be heard over greater distances.

WATCH: Thundersnow caught Live by Meteorologist T.J. DelSanto  ( if you don’t see video below, click here » )

Watch Meteorologist T.J. Del Santo on CBS This Morning: http://www.cbsnews.com/videos/50-million-in-northeast-inundated-by-winter-storm

Tim White ( twhite@wpri.com ) is the Target 12 investigative reporter and host of Newsmakers for WPRI 12 and Fox Providence. Follow him on Twitter and on Facebook