New ‘Megaflash Lightning’ Records Are the Definition of Extreme

New ‘Megaflash Lightning’ Records Are the Definition of Extreme
An example of cloud-to-cloud lightning (not related to the lightning megaflashes documented in the new paper). (Photo: ThaliaTraianou, Fair Use)

The World Meteorological Organisation is recognising two new world records having to do with lightning, one for the longest duration and the other for the longest single flash.

The new records were observed in two separate locations, but both occurred in hotspots known to produce extreme lightning events: the Great Plains of North America and La Plata basin in South America. The skies above these regions host Mesoscale Convective System (MCS) thunderstorms, in which a collection of thunderstorms effectively act as a single system. The superbolts produced by MCSs will sometimes move horizontally at high altitudes, jumping from cloud to cloud and for distances in excess of 100 km or more.

The World Meteorological Organisation announced the new records on February 1. This specialised agency of the UN is the official gatekeeper of such matters, tracking weather extremes having to do with pressure, rain, hail, wind, lightning, tornadoes, and tropical storms. Details of the two new records were published in the Bulletin of the American Meteorological Society.

On June 18, 2020, a single lightning megaflash lasted for a whopping 17.102 seconds, which it did above the skies of Uruguay and northern Argentina. This is now the new long-duration standard. The previous record dates back to March 2019, when a single flash over northern Argentina persisted for 16.73 seconds.

Image: WMOImage: WMO

On April 29, 2020, a single lightning flash originating near Houston, Texas, travelled an astounding 768 km to southeastern Mississippi. That’s roughly equal to the distance between New York City and Columbus, Ohio. The new record is 60 km longer than the previous record, which was recorded over southern Brazil on October 31, 2018.

“These are extraordinary records from single lightning flash events,” Randall Cerveny, rapporteur of Weather and Climate Extremes for WMO, said in a press release. “Environmental extremes are living measurements of the power of nature, as well as scientific progress in being able to make such assessments.”

The new records were captured by the Geostationary Lightning Mappers on the GOES-16 and 17 satellites. These instruments, along with weather satellites covering Europe and Asia, are now providing near-global coverage of lightning flashes. Cerveny said it’s “likely that even greater extremes still exist, and that we will be able to observe them as lightning detection technology improves.” Mesoscale lightning flashes were first detected in the 1950s, and records are continually being broken as a result of improved detection techniques.

The date of the previous long-distance record comes as quite a shock to me, but for a personal reason. On that very date, Halloween 2018, I travelled from Toronto to São Paulo, and after a short layover there, flew to Rio de Janeiro. We obviously survived the journey, but I vividly remember the trip to Rio as being among the most uncomfortable and turbulent flights I’ve ever been on. My mind is absolutely blown that a record-setting lightning megaflash occurred on that very day in the exact region where I was travelling.

We were probably safe during that flight, but we need to be wary of such storms and the potential for lightning to inflict harm on human life and property. As WMO Secretary-General Petteri Taalas noted in the press release, lightning is “a major hazard that claims many lives every year.” Accordingly, the new findings “highlight important public lightning safety concerns for electrified clouds where flashes can travel extremely large distances.”