Thundersnow! The mere mention of the Washington area’s Wednesday night weather phenomenon conjures Nordic gods and Bjork lyrics — but in fact it’s not nearly so strange. “It’s basically a light flash that occurs during a snowstorm,” said Walt Petersen, a physical scientist at NASA Marshall Space Flight Center. “It’s relatively rare in the sense of observing it … but it’s not Armageddon.”
Of about 10 million cloud-to-ground lightning flashes each year in the United States, fewer than a tenth of a percent of them are associated with thundersnow, Petersen said. Still, that’s up to 1,000 flashes.
In layperson terms, thundersnow tends to occur when the temperature teeters around the freezing point, and particles high in the atmosphere — some more icy than wet, and some more wet than icy — collide. The friction creates lightning.
Snowstorms usually don’t have the same intense swirling air currents typical of summertime thunderstorms, Petersen said. And it’s those intense air currents at 20,000 to 30,000 feet above the Earth that force the electrifying collisions. On Wednesday, the air far above Washington did just that.
Patrick Market, a professor of atmospheric science at the University of Missouri, spent some time in the 1990s braving both the cold and the lightning to chase after thundersnow.
He didn’t actually catch it, he said with some dismay, but he learned a little bit more about the phenomenon.
“There’s enhanced rising motion [in the air], not drastically different than what we experience in the summertime,” he said. “There’s concentrated vertical motion — that’s one of the things we figured out.”
And to what end? Market’s work, along with others, has been put to use to make better forecasts. And based on yesterday’s near-flawless predictions of when and where the snow would fall, the work has been put to good use.
“We do understand now what’s going on [with predictions] far better than even 15 or 20 years ago,” Market said.
Unfortunately, knowing what was coming didn’t do much to stop the utter chaos that came along D.C.-area roadways. But at least thundersnow provided some visual entertainment thoroughout the 12-hour commutes.
