A lightning flash that extended from near Dallas, Texas, to Kansas City, Missouri, now holds the record for the longest lightning discharge ever recorded. Known as a “megaflash,” the lightning discharge spanned some 515 miles (829 kilometers) and lasted 7.39 seconds. It included over a hundred individual cloud-to-ground strikes that were part of a large storm system extending from Minnesota to Texas. 
 

Most lightning flashes are much shorter – 10 miles or less – but discharges that travel hundreds of miles occur frequently enough to be detected from space and are often seen in the Great Plains area of the United States. Beyond the inherent interest in their unusual length and duration, meteorologists are studying these megaflashes to learn more about the mysteries of lightning, to develop new approaches for predicting the risk of severe storms – and to provide public warning of lightning bolts that may occur unexpectedly long after the storm front spawning them has passed.

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The new record megaflash was identified in data from a storm that occurred in October 2017. The flash produced more than 116 cloud-to-ground lightning strikes from a lengthy and complex series of jagged paths woven through the clouds. It was not found earlier because of how the data was originally processed, but was finally identified when the satellite data was re-analyzed in 2024.
 

The 515-mile megaflash has now been recognized by the World Meteorological Organization (WMO), and a paper reporting it has been accepted for publication in the journal Bulletin of the American Meteorological Society. The study that produced the discovery was led by scientists at the Georgia Tech Research Institute (GTRI), with support from the NASA Marshall Space Flight Center and Georgia Tech’s Center for Space Technology and Research (CSTAR). 
 

“These very large flashes, like this record megaflash, represent a unique kind of lightning we don’t see in many storms, but when they do occur, they can be individually very impactful,” said Michael Peterson, a meteorologist and senior research scientist who led the study in GTRI’s Severe Storms Research Center (SSRC). "These storms tend to occur as large organized systems that extend for long distances from the Great Plains eastward to the Southeast and even into Georgia. They tend to form intense convective lines with expansive regions of trailing electrified stratiform clouds which these flashes propagate through. While these very large lightning flashes are individually quite rare, they can occur in the kinds of thunderstorms that seem relatively common.”
 

The researchers hope that studying these very long flashes will help improve their ability to predict which thunderstorms may spin off violent weather.
 

“We believe lightning can be a useful diagnostic tool for understanding the behavior and potential for severe weather from thunderstorms,” Peterson explained. “But there are still a lot of questions left unanswered about the nature of these connections, and these megaflashes are an important part of that uncertainty. We don’t understand what factors cause them in the first place, and how some reach a scale of more than 500 miles.”
 

Storms producing megaflashes appear similar to ordinary storm fronts, which can sweep through an area with heavy rain, damaging hail, high winds, and tornadoes. After those threats pass, rain or overcast skies can linger, and people in the affected area may assume that the danger is over. But the clouds maintain their electrical charge for hours after thunderstorms that are part of the main storm front pass.
 

“Because the clouds remain electrified, they can still produce lightning, and that’s what we see in these very large horizontal discharges that can put down a hundred or so cloud-to-ground strokes, all along the horizontal path of the megaflash,” Peterson said. “The lightning seems to strike out of the gray, which is similar to the description of a ‘bolt from the blue’ that might seem to come from a blue sky overhead, when the distant thunderstorm spawning the flash may not even be visible. That’s the heart of the hazard to the general public from this type of lightning.”
 

Researchers have been studying megaflashes for a number of years, most recently utilizing data produced by the Geostationary Lightning Mapper (GLM) sensor – a type of specialized high-speed camera – on the National Oceanic and Atmospheric Administration’s (NOAA) Geostationary Operational Environmental Satellites (GOES). The previous record-long flash took place in April 2020 and traveled for approximately 477 miles.
 

“With the increasing development of new scientific methods of determining lightning events – particularly megaflash events – and the skilled interpretation of dedicated atmospheric scientists, we are achieving a new and improved understanding of our atmosphere’s operation and changes, said Randy Cerveny, another co-author of the paper and an Arizona State University President’s Professor in the School of Geographical Sciences and Urban Planning. “Such an understanding is critical in these times of ever-increasing dangers resulting from changes to our environment.”
 

Peterson and collaborators, including SSRC colleague Research Scientist Jessica Losego, hope to learn more about how these megaflashes develop, and why only certain thunderstorms produce them. Gathering that data will require additional instrumentation, including the planned development of a ground-based field project in the Great Plains to supplement the GOES data.
 

“Understanding lightning, including these very large flashes, is important to the severe storms research that we do here in Georgia, because lightning behavior is one of the key tools we have to relate thunderstorm updrafts to the impacts that they produce,” Peterson said. “A lot of work has been put in across the community to be able to look at the amount of lightning produced when we get a storm and understand something about that storm’s potential for generating tornadoes. But that’s not the only metric that we have available. We’re looking for how to make the best use of all the information we have, including flash sizes, flash rates, and electromagnetic outputs from lightning to get a better sense of what is going on at the heart of the storm.”
 

In addition to those already mentioned, coauthors of the paper include Rachel Albrecht (Universidade de São Paulo), Sven-Erik Enno (EUMETSAT), Ron Holle (Holle Meteorology & Photography), Timothy Lang (NASA Marshall Space Flight Center), Timothy Logan (Texas A&M University), Walter Lyons (FMA Research), Joan Montanya (Polytechnic University of Catalonia), Shriram Sharma (Tribhuvan University), and Yoav Yair (Reichman University).

Link to World Meteorological Organization news release
 

About the SSRC: The Georgia Tech Research Institute’s Severe Storms Research Center (SSRC) is actively engaged in developing alternative methods of detecting and forecasting severe local storms and exploring improvements to existing storm prediction and sensor technology. The SSRC was established in 1999 after a task force formed by Georgia’s governor recommended creating an organization to coordinate the state’s severe weather forecasting, with funding from the Georgia Emergency Management Agency (GEMA), the Federal Emergency Management Agency (FEMA), and the state of Georgia. For more information, visit https://severestorms.gatech.edu/
 

Writer: John Toon (john.toon@gtri.gatech.edu)
GTRI Communications
Georgia Tech Research Institute
Atlanta, Georgia USA

About the Georgia Tech Research Institute (GTRI)
The Georgia Tech Research Institute (GTRI) is the nonprofit, applied research division of the Georgia Institute of Technology (Georgia Tech). Founded in 1934 as the Engineering Experiment Station, GTRI has grown to more than 3,000 employees, supporting eight laboratories in over 20 locations around the country and performing more than $919 million of problem-solving research annually for government and industry. GTRI's renowned researchers combine science, engineering, economics, policy, and technical expertise to solve complex problems for the U.S. federal government, state, and industry.