Two megarays recorded in North America and South America respectively have been validated by the World Meteorological Organization as new world records in this meteorological event, which particularly affects the American continent.

The new unprecedented discharges fell in areas particularly sensitive to storms known as mesoscale convective systems, whose dynamics make it possible for extraordinary megarays to occur, namely the Great Plains in North America and the La Plata Basin in South America.

The WMO Committee in charge of extreme weather and climate events, which keeps an official record of these at regional, hemispheric and global scales, recognized these records.

The longest lightning ever detected

Specifically, the record for the longest single lightning strike has been broken, as it covered a horizontal distance of about 768 kilometers (+- a margin of 8 kilometers) across the southern United States on April 29, 2020. That record is equivalent to the distance between the U.S. cities of New York and Columbus (Ohio), or between London and the German city of Hamburg.

The new value for the longest distance traveled by a lightning strike ever detected exceeds the previous record by 60 kilometers, given that on that occasion the phenomenon occurred over 709 (+- 8 kilometers) across southern Brazil on October 31, 2018.

The longest-lasting lightning strike

On the other hand, the record for the longest individual lightning strike duration has also been broken, as its discharge occurred continuously for 17.102 (+- 0.002 seconds) during a storm that formed over Uruguay and northern Argentina on June 18, 2020.

The previous record for the longest duration of a megathunderstorm was observed in a lightning stroke whose discharge occurred continuously for 16.73 seconds in northern Argentina on March 4, 2019. This is 0.37 seconds shorter than the current record.

The danger of lightning

Lightning is a major hazard that claims numerous lives each year. These records highlight issues of public safety importance with respect to electrified clouds where lightning can travel enormous distances. The only places where lightning is not a threat are large buildings with wiring and plumbing networks, not structures such as those on the beach or at bus stops.
Another place considered safe is inside vehicles with fully enclosed metal roofs, not buggies or motorcycles.

According to the data collected in the WMO Extreme Weather and Climate File, the organization has previously verified other lightning-related phenomena such as direct lightning strikes, like the 1975 lightning strike in Zimbabwe that killed 21 people who were huddled in a hut seeking shelter.

Also included in the archive is the indirect lightning strike in 1994 that killed 469 people in Dronka, Egypt, when lightning struck a fuel tank farm, causing the flaming liquid to spill into the town.

Lightning study

Previous assessments to determine the longest lightning strike and the longest duration lightning strike used data collected by ground-based lightning discharge mapping (LMA) networks. Many lightning scientists recognized that current LMA networks can only observe these phenomena up to certain limits. Observing megarays beyond those thresholds would require mapping technology with a wider range.

Despite having a major impact on our daily lives, lightning is an amazingly elusive and complex natural phenomenon. We now have excellent measurements of its many facets, and this allows us to discover new and surprising aspects of its behavior. Now that we have a solid record of these monster lightning strikes, we can begin to understand how they are produced and estimate the inordinate effects they have.

Space-based instruments, meanwhile, will provide near-global coverage of total lightning activity, both cloud discharges and cloud-to-ground lightning.

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