The two lightning records confirmed by World Meteorological Organization last week sent shockwaves across the science community and raised the bar for what’s to be expected as monitoring technology improves.
The records were for length and duration. The length record was set April 29 of last year with a megaflash that stretched 477 miles from Mississippi to Texas and across the northern tip of the Gulf of Mexico.
The duration record, set June 18 of last year, was for a megaflash that lasted 17.1 seconds, eclipsing the previous title holder, which was 16.7 seconds, by a fraction of a second. It occurred in the La Plata Basin in South America.
Both occurred in lightning hot spots, according to scientists, areas that frequently see megaflash events, which are distinct from normal lightning by their sheer size.
While their measurements are impressive, what’s more important, scientists say, is that far-reaching and prolonged storms such as these illustrate the potential hazards and dangers of megaflash storms. Rather than just strikes that hit one specific area, these flashes can stretch vast distances and pose serious dangers to people, even if they aren’t directly under the lightning.
“I think the really important, general public aspect of this is what this means in terms of lightning safety,” said Randall S. Cerveny, a professor of geographical sciences at Arizona State University and rapporteur on extreme records for the United Nations World Meteorological Organization. “It really emphasizes the fact that lightning can hit places far away from where it originates.”
Scientists are still figuring out what causes such megastorms, but they know such phenomena occur during convection thunderstorms, which are larger heat-based storms. This type of storm frequents Arizona during the summer monsoon, although Cerveny says weather observers have never seen megaflashes of either of these magnitudes in the Southwest.
Cerveny and other experts say these new records are not a symptom of climate change, and caution that storms of this nature could have been happening all along. What is new is the technology used to monitor such weather events.
Seeing weather in a new light
Advances in technology are allowing scientists to see weather in a new light, with finer grain details. Meteorologists used to study storms using location-specific technology. Now they use a combination of ground-based monitoring and Geostationary Lightning Mappers, instruments on Geostationary Operational Environmental Satellites that were first used in 2016.
The instruments have increased knowledge of when and where megaflashes occur, said Michael Peterson, an atmospheric scientist at the Los Alamos National Laboratory in New Mexico. Unlike previous satellites and ground-based technology, which look at smaller geographic areas, the GLMs allow scientists to see storms across continents and regions from space.
Both techniques have their advantages and disadvantages, said Timothy Logan, director of the Houston Lightning Mapping Array Network at Texas A&M University. Ground-based devices use radio waves to scan the air for electric currents across local areas. Satellites allow scientists to actually peer into clouds across the globe.
With radio, “you lose the signal after a certain distance, but you catch everything within the range of detection,” Logan said, “But the optical detector on the geostationary satellite has to peek through a cloud. So the flash would have to be bright enough to be detected.”
The record flash along the Gulf Coast was measured using the “maximum great circle distance methodology” for consistency with past records. This approach computes the distance between the two most distant points in the flash. Despite its length, Cerveny said it would have been difficult to see.
“A lot of the flash was buried within the massive thunderstorm that was across the area. You would not have seen the first part of it all the way to the end of it.” he said. “And since it was stretching for so long, and it branched out to cover such an enormous area, you would not have personally been able to see the whole entire show there.”
The megaflash was also brief. At 8.55 seconds, it would have been a sudden burst of light that flashed quickly before burning out. The time, so early in the day, would have also made it tricky to see.
“The megaflash was around nine in the morning, Central Time,” Logan said. “The storm passed through Bryan college station at around two or three (a.m.). It woke everybody up. All the meteorology nerds were tweeting and putting out information.”
The safety hazards of lightning
The National Weather Service reports that nearly 50 people die from lightning strikes each year in the U.S. Notable WMO extremes include a single lightning strike in 1975 that killed 21 people in Zimbabwe and an indirect lightning strike that killed 469 people in Egypt when it struck an oil tanker, causing flames to engulf a town in 1994.
But Ron Holle, a meteorologist from Tucson, who used to work for the National Oceanic and Atmospheric Administration, says the U.S. number is over a 30-year average. Advances in technology, education, improved structures and medical care have helped reduce that number. Last year, there were only 13 instances of lightning-related deaths in the US, Holle said.
There are five types of human-lightning incidences: direct strikes, side flashes, ground currents, contact voltage when the current surge travels along wires and metal surfaces, and upward leaders, which come up within half a mile of where the original strike occurred.
“The one that you probably are thinking of is lightning comes down from above, hits you in the head — hardly ever, ever happens. It’s probably 3 to 5% of the time,” Holle said. “The most common one most likely is ground currents where it hits nearby in an open field and travels across the ground. That’s probably 30 to 40% of the time.”
Previous record: A lightning bolt 440 miles long? ASU scientist verifies flash
If someone finds themselves in a thunderstorm, experts like Holle urge caution since lightning can move over great distances so swiftly. The only real safe place is a building or structure with plumbing and wiring, which allow lightning to find easy pathways to the ground. If a structure with such infrastructure is not available, a closed-top car is recommended as lightning is more likely to travel around the vehicle and not through it.
Scientists anticipate many more records will be documented as monitoring efforts improve and as more countries scale up their technology. Efforts are already underway in Europe and Asia to deploy similar GLM-type satellites.
“In addition to our satellites, there are some international partners in lightning science who are launching similar or have launched similar instruments to GLM to view other parts of the globe,” Peterson said. “It’s really exciting to get this expanded coverage because lightning is a global phenomenon.”
Lindsey Botts is an environmental reporter for The Arizona Republic/azcentral. Follow his reporting on Twitter at @lkbotts and Lkbotts on Instagram. Tell him about stories at firstname.lastname@example.org
Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at environment.azcentral.com and @azcenvironment on Facebook, Twitter and Instagram.
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