If you awoke in a bleary-eyed panic on Monday morning, wondering why someone was setting off fireworks directly above your bedroom, you’re not alone.
Shortly before 6 a.m., as lightning lashed at the World Trade Center, blasts of thunder pummeled the eardrums of sleeping New Yorkers.
So what happened? According to multiple meteorologists who spoke to Gothamist, the ear-splitting wake-up call can be tracked to a phenomenon known as thermal inversion.
A reversal of normal temperature behavior, an inversion happens when a layer of warm air traps cold air directly below it – essentially turning our streetscape into nature’s Motorhead show.
As John Homenuk, a meteorologist at New York Metro Weather, explains: “This inversion can act like a lid in the atmosphere, so when lightning occurs the sound waves are trapped underneath it and they echo back to us on the ground, making them sound much louder than normal.”
The inversion also allows for the sound waves to travel greater distances – possibly explaining why the ear-splitting thunder stretched from Brooklyn across New Jersey.
While inversion itself isn’t terribly uncommon, a range of factors, including its placement and the slow-moving thunderstorm, combined to make the experience memorable for many.
“It probably happens a few times a year, but when it happens over a major metropolitan area like New York City, it seems a little more unusual,” said Dominick Ramunni, a meteorologist with the National Weather Service.
This isn’t the first time that a temperature inversion has cultivated a shared sensory experience. Back in 2005, in the early days of what would later become a years-long citywide mystery, an inversion layer was suspected of helping trap the smell of maple syrup within nose-range of New Yorkers and New Jerseyans.