The longest ever lightning strike

The World Meteorological Organisation (WMO) has announced its confirmation of the longest ever lightning strike, a gargantuan mega-bolt that stretched for more than 750km across three American states.

The flash actually occurred in April 2020, and was seen across a 768km stretch spanning Texas, Louisiana and Mississippi. This beat the previous record holder, a 2018 bolt in Brazil that stretched for 709km.

But how do you measure the length of a lightning bolt? One scientist, with a measuring tape, running really fast? 

Thankfully, no. The WMO were able to measure the mega-flash’s length by using Geostationary Lightning Mappers (GLMs) on board the US National Oceanic and Atmospheric Administration’s (NOAA) latest GOES-16/17 satellites.

And that’s not the only new record-holder announced this week. In the same study, the WMO found a new candidate for the longest lightning flash by duration, a 17-second continuous burst of lightning from a thunderstorm over Uruguay and northern Argentina in June 2020.

That flash pipped the previous record-holder, a 16.73-second flash over Argentina in March 2019.

Mega-flashes like these two newly certified beasts are uncommon. They require massive, highly electrified storm clouds that discharge at sufficiently slow rates to enable these huge flashes to travel across such long distances, and for such a long time.

In fact, a particular type of storm system, known as a Mesoscale Convective System (MCS), meets the criteria for these mega-flashes, but generally MSCs rarely produce lightning strikes at such extreme scales – in fact, the Great Plains of North America and the La Plata basin in South America are the only places MSCs producing these epic flashes have ever been observed.  

“These are extraordinary records from single lightning flash events,” says Randall Cerveny, rapporteur of weather and climate extremes for WMO. “Environmental extremes are living measurements of the power of nature, as well as scientific progress in being able to make such assessments.

“It is likely that even greater extremes still exist, and that we will be able to observe them as lightning detection technology improves.” 

The findings are published in the Bulletin of the American Meteorological Society.

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