Shared from the 2/17/2017 The Providence Journal eEdition

MY TURN SCOTT TURNER

Tough, intimidating thundersnow

Picture

Scene beneath a streetlamp on the East Side of Providence immediately after the nor’easter passed. [KAREN WARGO]

As the nor’easter’s gale-force winds drove blinding snow up our street, a low, long-lasting rumble, suggested that a plow truck the size of a tractor-trailer was slowly passing our home.

“That, was thunder,” I said.

“No way,” responded Noah, our 16-year-old son.

“That could not be thunder,” my wife, Karen, said. “Could it?”

Interestingly, it was a muffled roar. But I was sure it wasn’t anything mechanical. It certainly did not come from a jet or aircraft flying through such a terrific storm.

And then, it bellowed again outside. This sound was longer and louder than the first one.

Although this second rumble also seemed somewhat subdued, there was no way that it was produced by any plow.

I had heard thunder in a snowstorm before, but never was I so aware of the delicate hush that could accompany it — like the effect that a mute can have on the end of a trumpet.

Any uncertainty about the sound ended the split second after lightning struck beyond our backyard.

Lightning during a blizzard appears exceptionally bright, given the whiteness all around it. The flash, I’ve read, actually reflects off falling snow and snow on the ground, to produce a powerful brightness. The thunder that followed immediately was forceful enough to shake the house.

When I looked up the phenomenon called “thundersnow,” I learned that dense, fluffy snow could limit both the distance that lightning can be seen and significantly mute the distance over which thunder travels.

In a normal thunderstorm, thunder can be heard for several miles in all directions. Thunder’s reach in a blizzard is often much shorter, maybe two miles max.

Given that snow in a whiteout restricts lightning and muffles thunder, that lightning strike behind our home was likely very close.

When thundersnow shows up, it is often accompanied by high winds and rapidly accumulating snow, falling 2 to 4 inches per hour.

Sometimes, thundersnow is also associated with the presence of hail, as well as graupel. “Also called soft hail or snow pellets, graupel is precipitation that forms when super-cooled droplets of water are collected and freeze on falling snowflakes,” notes Wikipedia.

Snowstorm lightning and thunder happen the same way they do in rainstorms, when warm, moist air rises from the ground, colliding with colder air aloft.

Thundersnow doesn’t happen very often, maybe five to 10 times a year across the entire United States. It’s a well-deserved name for an intense, powerful and rapidly moving tempest.

— Scott Turner’s (scottturnerster@gmail.com) nature column appears here most Fridays.

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