New record for a lightning strike in the United States: it extended horizontally for 829 kilometers. Here’s how we measured it
A recent analysis confirmed that a single lightning bolt – called a “megaflash” – traveled horizontally approximately 500 miles (829 kilometers) across the central United States, setting a new world record for length. The term “megaflash” is used by scientists to describe single flash discharges whose horizontal length exceeds 100 kilometers.
This event far surpasses that. In this case, the discharge was recorded within a large mesoscale convective system (MCS) — a large storm complex that can span multiple cloud states where electrified clouds create favorable conditions for very large horizontal discharges.
How did we measure it? Lead researcher Michael Peterson (of the Georgia Tech Research Institute – Severe Storms Research Center) and his team used satellite data, specifically from the instrument Geostationary Lightning Mapper (GLM) on board the GOES‑16 satellite, to track the discharge continuously. To avoid errors due to multiple overlapping streams, the team applied improved “clustering methods” that group isolated light pulses into what is really a single continuous flash. To better understand this technique it must be said that when lightning is formed, it does not emit a single constant light, but a series of very rapid light pulses (in the order of milliseconds). Satellites like the Geostationary Lightning Mapper (used in this study) record each small flash of light as a separate “light event.”
… and certified. The problem is that if a burst is very long (like “megaflashes”), the satellite might interpret those hundreds or thousands of consecutive pulses as multiple distinct lightning strikes, rather than a single event spanning hundreds of kilometers. It is for this reason that atmospheric physicists have developed a mathematical system capable of analyzing the position, time and light energy of each pulse observed by the satellite, as well as recognizing when many pulses close in space and time are part of the same discharge channel.
Finally, they merge (“clustering”) them into one continuous lightning strike, rather than considering them as separate events. The official recorded measurement is 829 ± 8 km in length, from east Texas to near Kansas City, Missouri. The record surpassed the previous one of 768 ± 8 km (recorded in April 2020 in the USA) by approximately 61 kilometers.
What makes these lightning bolts special. Discharges of this type (megaflash) are very rare: it is estimated that less than 1% of storms produce a discharge with these characteristics.
They originate in very large convective systems, with extensive cloud cover, large-scale accumulated electrical charges, and horizontal charge “lakes” that allow the discharge to propagate laterally rather than simply vertically.
The fact that they can extend for hundreds of kilometers means that the associated risk is not limited to the “heart” of the storm: the discharge can hit areas very distant from the active convective core.
In the past. Prior to this measurement, the previous record was 768 km in the United States (April 2020). Extreme megaflashes have been observed in South America: for example, over the Río de la Plata basin (Argentina/Uruguay) there was a flash that lasted a record 17.1 seconds, although not necessarily the maximum length recorded here.
Modern satellite technologies are expanding our ability to detect these events: many megaflashes have probably occurred in the past, but were not fully visible by traditional ground-based detection systems.
Practical and scientific implications. The event provides useful indications in various respects ranging from public safety (given that a discharge can spread for hundreds of kilometers. Current lightning warning protocols must take into account potential strikes well away from the core of the storm), to climate and risk modeling (these types of lightning influence the chemistry of the atmosphere – for example the production of nitrogen oxides – and can fuel wildfires forests or hit aircraft. Models must take into account “horizontal” and not just vertical discharges), up to research on storms (studying megaflashes means better understanding how electrical charges accumulate and discharge in extreme convective systems, improving our understanding of large-scale storms and their effects).
