Megaflash
It's a real thing.
A megaflash is a continuous lightning flash that spans over 100km in length.
Let that sink in. If it were horizontal, it would reach into space.
My father was particularly fond of describing something extremely fast as "faster than greased lightning," a phrase that captures the essence of speed. And with good reason - lightning flashes typically travel at 270,000 mph and last only a few seconds.
However, under certain rare conditions, a lightning flash can persist. In storms where the electrical field is relatively weak, charges can accumulate gradually. This slow buildup allows for an increase in magnitude before a flash occurs, similar to how slowly and carefully adding pieces to a Jenga tower enables it to grow taller. In this analogy, the Jenga blocks represent the differentially charged (negative and positive) regions within the clouds.
Eventually, a spark is triggered. The charges meet, neutralize each other, and create an electrified thin1 tube of plasma that heats up the air around it to about 30,000 °C (54,000K °F). The superheated air around this tube expands explosively, creating thunder.
Mega Flash is a grammar book series written for people with 2nd-5th grade grammar skills. Much to the relief of Grammar.ly’s servers, I’ve ordered one of each. (McGraw Hill)
For detecting these megaflashes, three systems stand out: 3D Lightning Mapping Arrays (LMAs), which detect lightning static through multiple VHF radio towers; the National Lightning Detection Network (NLDN), a network of low-frequency radio sensors across the United States; and the Geostationary Lightning Mappers (GLMs) on the GOES-16/17 satellites, which monitor the Earth for flashes in the near-infrared.
The GLM, looking like a Dalek that just got back from the vet. (NOAA)
With over 3 million lightning flashes occurring daily, outliers are inevitable. In 2017, the World Meteorological Society established criteria for determining extremes in lightning reports. In doing so, they established the first records in the subject.
Hold My Flash
There are two main events in the Megaflash Olympics: distance and duration. The current record for the longest continuous lightning flash in distance is 768km (477 miles) reaching along the Gulf Coast of Texas to Mississippi on April 29, 2020. The current record for the longest lightning flash in duration is 17.1 seconds on June 18, 2020, in a storm along the Argentina-Uruguay border.
The longest lightning flash by distance ever recorded (to date), extending from Texas to Mississippi. (Bulletin of the American Meteorological Society 103, 4; 10.1175/BAMS-D-21-0254.1)
The longest lightning flash by duration (17.1 seconds) ever recorded (to date), extending along the Argentina/Uruguay border. (Bulletin of the American Meteorological Society 103, 4; 10.1175/BAMS-D-21-0254.1)
You can bet these records won’t last. The GLMs continue to monitor storms 24x7 but with a field-of-view limited mostly to the western hemisphere. New equipment on other satellites such as the Fengyun-4A and Meteostat Third Generation series are expanding lightning coverage to other parts of the world. The race is on.
Realtime animation of a former record holder. This megaflash extended at least 500km from Texas to Kansas. The lower left data shows the evolution of two storm systems over eastern Oklahoma – the megaflash is the one on the left. The data in the lower right shows the altitude of flashes in both storms. (Lyons, et al., 2020; Bulletin of the American Meteorological Society 101, 1; 10.1175/BAMS-D-19-0033.1)
And now for something not that different…
The American Meteorological Society maintains a peer-reviewed Glossary of Meteorology with over 12,000 terms in it. The AMS recently launched a pilot project to translate it into Spanish. As part of that project, 50 of the most popular terms were published in Spanish. Megaflash was one of them. Below is the definition of Megadestello en Español – which I think sounds even cooler than Megaflash.
Megadestello
Es un relámpago continuo de mesoescala con una longitud de trayectoria horizontal de aproximadamente 100 km o más. Las tremendas distancias cubiertas por megadestellos también requieren largas duraciones del relámpago, típicamente de 5 s o más.
Los megadestellos típicamente ocurren en las regiones estratiformes de los sistemas convectivos de mesoescala (MCS, por sus siglas en inglés). Estos destellos expansivos pueden producir uno o más impactos de nube a tierra (CG, por sus siglas en inglés) a lo largo de sus trayectorias. Algunos CG associados con megadestellos tienen grandes cambios en el momento de carga o corrientes pico que resultan en superrelámpagos, espectros rojos o descargas de relámpagos ascendentes disparadas por relámpagos (LTUL, por sus siglas en inglés) desde estructuras altas.
En junio de 2020 la Organización Meteorológica Mundial anunció la certificación de nuevos registros globales de rayos extremos para megadestellos después de la identificación de megadestellos de más de 700 km de longitud y 16 s de duración sobre Argentina y el.
For more WWaT on lightning, check out our newsletter from January 30.
Additional contributions by Dr. Chad Kauffman.
Lightning bolts are usually only a few centimeters in diameter.