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Megaflash lightning extremes

The World Meteorological Organization (WMO) committee of experts has established two new world records for the longest reported distance and the longest reported duration for a single lightning flash in, respectively, Brazil and Argentina.

The new records for “megaflashes”, verified with new satellite lightning imagery technology, more than double the previous values measured in the United States of America and France. The findings were published by the American Geophysical Union’s Geophysical Research Letters ahead of International Lightning Safety Day on 28 June.

WMO’s Committee on Weather and Climate Extremes, which maintains official records of global, hemispheric and regional extremes found that:

  • The world’s greatest extent for a single lightning flash is a single flash that covered a horizontal distance of 709 ± 8 km (440.6 ± 5 mi) across parts of southern Brazil on 31 October 2018.   This is equivalent to the distance between Boston and Washington DC in the United States of America or between London and the border of Switzerland near Basel.
  • The greatest duration for a single lightning flash is 16.73 seconds from a flash that developed continuously over northern Argentina on 4 March 2019.“These are extraordinary records from single lightning flash events. Environmental extremes are living measurements of what nature is capable, as well as scientific progress in being able to make such assessments. It is likely that even greater extremes still exist, and that we will be able to observe them as lightning detection technology improves,” said Professor Randall Cerveny, chief rapporteur of Weather and Climate Extremes for WMO.

    “This will provide valuable information for establishing limits to the scale of lightning – including megaflashes – for engineering, safety and scientific concerns,” he said.

    Lightning is a major hazard that claims many lives every year. The findings highlight important public lightning safety concerns for electrified clouds where flashes can travel extremely large distances (30-30 rule – if time between flash and thunder is less than 30 seconds, go inside! And wait 30 minutes after the last observed flash to resume outdoor activities).

    The previous record for the longest detected distance for a single lightning flash was for 321 km (199.5 miles) on 20 June 2007 across the U.S. state of Oklahoma. Both the previous and new record used the same maximum great circle distance methodology to measure flash extent.

    The previous record for duration was for a single lightning flash that lasted continuously for 7.74 seconds on 30 August 2012 over Provence-Alpes-Côte d’Azur, France.

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