In the southern United States, World Meteorological Organization’s Committee on Weather and Climate Extremes has officially recognised a single flash that covered a horizontal distance of around 770 km on 29 April 2020, which is “equivalent to the distance between New York City and Columbus Ohio in the United States or between London and the German city of Hamburg,” said the UN agency in a press release.
The other record announced was for the greatest duration for a single lightning flash – of around 17.102 seconds from the flash – that developed continuously through a thunderstorm over Uruguay and northern Argentina, on 18 June 2020. The findings were published in the Bulletin of the American Meteorological Society.
Other previously accepted WMO lightning extremes have been far more deadly, than spectacular: in Zimbabwe, in 1975, 21 people were killed by a single flash of lightning as they huddled for safety in a hut. An indirect lightning strike killed 469 people in Dronka Egypt when lightning struck a set of oil tanks, causing burning oil to flood the town in 1994. Lightning is a calamity that kills many every year. According to a report by the Indian government, 1,697 people died from lightning strikes between 2020 and 2021.
“These are extraordinary records from single lightning flash events. Environmental extremes are living measurements of the power of nature, as well as scientific progress in being able to make such assessments,” said Professor Randall Cerveny, rapporteur of Weather and Climate Extremes for WMO.
The head of WMO, Petteri Taalas, said of the new records, that lightning was a major hazard that claims many lives every year. “The findings highlight important public lightning safety concerns for electrified clouds where flashes can travel extremely large distances.”
The new record strikes occurred in hotspots for what are known as Mesoscale Convective System (MCS) thunderstorms, whose dynamics permit extraordinary mega lashes to occur – namely, the Great Plains in North America, and the La Plata basin in South America.
Be safe when you hear it
“The only lightning-safe locations are substantial buildings that have wiring and plumbing; not structures such as at a beach or bus stop,” cautioned Ron Holle, noted lightning specialist and committee member on these spectacular events. “The second reliably safe location is inside a fully enclosed metal-topped vehicle; not dune buggies or motorcycles. If lightning is within 10 km as found with reliable lightning data, go to the lightning safe building or vehicle. As these extreme cases show, lightning can arrive within seconds over a long distance, but they are embedded within larger thunderstorms, so be aware,” he adds.
Recent advances in space-based lightning mapping offer the ability to measure flash extent and duration continuously over broad geospatial domains, said WMO.