Massive 515-mile ‘megaflash’ lightning bolt sets world record

A super-sized lightning bolt struck scientists as something special.

Now, researchers have confirmed that a lightning strike from 2017 has broken a world record.

A single flash of lightning that stretched across the Great Plains, from eastern Texas all the way to Kansas City, Missouri, turned out to be a staggering 515 miles long.

A new report in the Bulletin of the American Meteorological Society documented the new lightning record, which beat the previous title holder, a 477-mile bolt from April 2020.

“We call it megaflash lightning and we’re just now figuring out the mechanics of how and why it occurs,” Randy Cerveny, an Arizona State University professor who worked on the study, said in a statement.

Megaflash lightning is defined as a lightning bolt that reaches beyond 62 miles in length. The average lightning bolt measures less than 10 miles long.

Less than 1% of thunderstorms produce megaflash lightning, according to satellite observations analyzed by Michael Peterson at the Georgia Tech Research Institute.

Megaflashes come from long-lived storms, typically those that brew for 14 hours or more, and they are massive in size — covering an area comparable to the state of New Jersey in square miles.

Cerveny and his colleagues measured the megaflash, which took place during a major thunderstorm in October 2017, with space-based instruments and a re-examination of satellite observations.

They reviewed data from the National Oceanic and Atmospheric Administration’s GOES-16 satellite, which has a lightning mapper that detects about one million lightning bolts per day.

“Our weather satellites carry very exacting lightning detection equipment that we can use [to] document to the millisecond when a lightning flash starts and how far it travels,” Cerveny said.

Lightning detection and measurement relied on ground-based networks of antennas for years. The antennas would detect the radio signals emitted by the lightning to estimate the location and travel speed based on the time it takes the signals to reach other antenna stations.

“It is likely that even greater extremes still exist, and that we will be able to observe them as additional high-quality lightning measurements accumulate over time,” Cerveny, who serves as rapporteur of weather and climate extremes for the World Meteorological Organization, explained.

Satellite-borne lightning detectors that have been in orbit since 2017 have made it possible for scientists to continuously detect lightning and accurately measure it at continental-scale distances.

“Adding continuous measurements from geostationary orbit was a major advance,” Peterson, first author of the report, said in a statement.

“We are now at a point where most of the global megaflash hotspots are covered by a geostationary satellite, and data processing techniques have improved to properly represent flashes in the vast quantity of observational data at all scales.”

While megaflashes are rare, Ceverny said that it’s not unusual for lightning strikes to reach 10 or 15 miles from the storm cloud it came from, which adds to the danger.

Lightning strikes kill about 20 to 30 people per year in the U.S. and injure hundreds more, and most of these injuries occur before and after the peak of a thunderstorm, not during it.

“That’s why you should wait at least half an hour after a thunderstorm passes before you go out and resume normal activities,” Cerveny said. “The storm that produces a lightning strike doesn’t have to be over the top of you.”