A lightning flash that stretched 515 miles (829km) across the United States has been confirmed as the longest ever recorded. The World Meteorological Organization (WMO) announced the record for the flash, which occurred on 22 October 2017 over the Great Plains, from east Texas to near Kansas City, Missouri.
The previous record of 768km was also recorded in the Great Plains, a hotspot for severe thunderstorms, on 29 April 2020. Advances in space-based mapping since 2016 have allowed scientists to measure lightning flashes over broader areas, using satellites like the National Oceanic and Atmospheric Administration's geostationary operational environmental satellite.
Michael J Peterson, lead author and evaluation committee member at the Georgia Institute of Technology, said: 'The extremes of what lightning is capable of is difficult to study because it pushes the boundaries of what we can practically observe. Adding continuous measurements from geostationary orbit was a major advance.'
The same technology also enabled the recording of the longest-duration lightning flash, which lasted 17.1 seconds over Uruguay and northern Argentina on 18 June 2020. Previously, ground-based sensors had limited the detection of such extremes.
Prof Randall Cerveny, WMO rapporteur of weather and climate extremes, warned: 'Everyday implications of these events are that lightning can travel quite long distances away from the parent thunderstorm. Because of this fact, people need to limit their outdoor activities during lightning-producing thunderstorms.' The WMO advises seeking shelter in substantial buildings or fully enclosed metal-topped vehicles during storms.
