June 20, 2007 was a landmark date in weather history. During a thunderstorm over Oklahoma, a lightning bolt extended 199.5 miles from outside Tulsa to the border of Texas. As Smithsonian reports, the spectacular phenomenon was recently confirmed by the World Meteorological Organization (WMO) as the longest lightning streak on record.
This particular bolt of lighting wasn’t what meteorologists are used to seeing from thunderstorms. The vast majority of lightning can be classified as “negative lightning”—this occurs when a negative charge strikes the ground from a cloud, typically spanning 6 miles at most.
The record-breaking Oklahoma bolt belonged to the 5 percent of lighting created by a positive charge. Positive lighting contains 10 times the energy of a negative bolt and generally spans up to 25 miles. As the Oklahoma case shows, extreme examples are sometimes produced under the right conditions. When the 200-mile bolt lit up the sky, it could be seen from as far away as Colorado.
The super-sized lightning wasn’t the only record recently recognized by the World Meteorological Organization. They also named a 7.74-second flash observed over Provence-Alpes-Côte d'Azur, France on August 30, 2012 as the longest lightning duration ever recorded.
These electrifying events mark the first time lightning has made it into WMO’s Archive of Weather and Climate Extremes. They’ve also changed the way the organization defines the phenomenon. According to the report from the Bulletin of the American Meteorological Society, the WMO committee has unanimously recommended revising the definition of lightning from a “series of electrical processes taking place within one second” to a “series of electrical processes taking place continuously.”
Better understanding what lightning is capable of can also help experts recommend more accurate safety guidelines in the face of extreme weather. The number of annual lightning deaths has been steadily declining since the 1940s, and that’s partly due to a raised awareness of weather safety. For now, the experts at WMO still recommend “when thunder roars, go indoors” as a universal rule of thumb.
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