Megaflash: World's longest lightning strike confirmed over Gulf of Mexico

 Equivalent to the distance from New York City to Columbus, Ohio, a single lightning strike has been certified as the longest ever recorded.

By John Murphy, AccuWeather staff writer

Published Jan. 31, 2022 7:00 PM EST | Updated Feb. 1, 2022 8:56 AM EST

On the morning of April 29, 2020, an intense line of severe storms was in its last hours onshore after sprawling across a 500-mile stretch and impacting several major cities. The squall line had already been blamed for large hail and damaging winds across several states and brought numerous power outages.

But the squall line storm had one more powerful punch to bring before moving ashore. As several bolts of lightning lit up the early morning sky across the south-central United States, one strike made a historical impact.

Lightning as viewed by the GOES-16 weather satellite during severe thunderstorms across the central U.S. Apr. 28-29, 2020, the date of the new record. (NOAA)

Just after 8:30 a.m., local time, on April 29, a single bolt of lightning associated with the storm arced from Texas out over the Gulf of Mexico into Louisiana and Mississippi, covering an astonishing horizontal distance of around 477 miles, beating the previous record in 2018.

Scientists at the World Meteorological Organization (WMO) confirmed the 2019 south-central U.S. "megaflash," a name given to lightning discharges that reach hundreds of kilometers in length, as the longest single flash ever recorded.

Ominous clouds loom over Jenks, Oklahoma, on April 28, 2020 as a severe squall line moved through the area. The storm would later create the longest-traveling lightning strike ever (Twitter/ @MattCoo24396976)

Previously, the WMO attributed a 440-mile-long strike in southern Brazil that occurred on Halloween night in 2018 as the longest single lightning strike.

The WMO had previously confirmed another 2020 lightning record in Uruguay and northern Argentina, which remains the greatest duration for a single lightning flash. The organization reported the lightning flash that lasted nearly 17 seconds on June 18 of that year was the greatest duration ever recorded.

AccuWeather national radar from around the time the record strike occurred on the morning of April 29, 2020.

“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. It is likely that even greater extremes still exist, and that we will be able to observe them as lightning detection technology improves,” said Professor Randall Cerveny, rapporteur of Weather and Climate Extremes for WMO.

There wasn't a lot of severe weather going on that day, but the record strike occurred in a lightning hotspot, a Mesoscale Convection System (MCS), which has dynamics that permit these extreme megaflashes to occur.

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“These extremely large and long-duration lightning events were not isolated but happened during active thunderstorms," said lightning specialist and committee member Ron Holle.

Recent advances in space-based lightning mapping have given lightning scientists the ability to measure flash extent continuously over broad geospatial domains, according to the WMO.

“The GOES-EAST weather satellite is equipped with the Geostationary Lightning Mapper (GLM), a highly-sensitive instrument that can detect nearly every lightning bold in its field of view. It can even detect when larger meteors explode when entering Earth’s atmosphere,” AccuWeather Meteorologist and Staff Writer Brian Lada said.

A 477-mile-long lightning "megaflash" is recorded on April 29, 2020 (NOAA)

The satellite was the first of its kind to be capable of lightning detection. The satellite is in geostationary orbit about 22,000 miles above the Earth's surface, which Lada says allows the satellite to have a continuous view of almost all of the entire Western Hemisphere.

"Not only can the GLM instrument detect the frequency in which lightning flashes, but also how far a lightning bolt travels through the atmosphere. This has helped scientists identify record-setting lightning bolts in areas of the world where there are no ground-based lightning detection units,” said Lada.

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