"Stretched" Lightning

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"Stretched" Lightning

Unread post by NZ Thunderstorm Soc »

Here's a report about an article called "Megaflash lightning bolt spans 3 states" reported in STUFF yesterday.

A 'megaflash' bolt of lightning that spanned nearly 800 kilometres across 3 US states has set the record for the most far-reaching ever. The lightning occurred in the southern US in April 2020, extending 767.9km through Texas, Louisiana and Mississippi. It beat the old 2018 record set in Brazil by almost 64km. Ordinarily, lightning does not last all that longer than a second or stretch further than 16km. Randall Cervery at Arizona State University, said "This lightning-known as a 'megaflash' because of it's size- moved from cloud to cloud rather than to the ground.
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Re: "Stretched" Lightning

Unread post by Simon Culling »

The WMO have confirmed this as the longest single flash covering a horizontal distance of 768km. They have also confirmed the greatest duration of a lightning flash that occurred recently over Argentina/Uruguay as being of 17.1 seconds. Further details on these two events/records in this press release:

https://public.wmo.int/en/media/press-r ... ng-records
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Re: "Stretched" Lightning

Unread post by wembley »

Interesting to know the polarity of that bolt.
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Re: "Stretched" Lightning

Unread post by tgsnoopy »

wembley wrote: Sat 05/02/2022 11:44 Interesting to know the polarity of that bolt.
Umm, I'm not sure it would have one as such. Positive or negative is defined normally with respect to earth. The charge that builds up on thunderstorms is Negative on the bottom of the cloud & Positive at the top. Most lightning is Negative from the bottom of the cloud to earth. With Rain static (The droplet is charged and each drop slowly reduces the charge with respect to earth) and negative lightning slowly discharging the negative bottom of the cloud (with respect to earth) the top can become extremely positive (with respect to earth) and positive lightning can jump out of the top of the cloud to ground. That's unusual here, not so much in the tropics.

With typical intracloud lightning events they aren't discharging to earth, therefore I doubt they could be formally classified as such. However I guess you could consider them all positive based on the direction of current flow, even though they don't touch earth. It gets real hard with the big events where some parts trigger others so it will have multiple discharges that are inter-related.It's possible a smaller growing CB might have higher charge on its top than a dying taller CBs top and a discharge between them could be negative, whereas It should normally be positive in that scenario.

Sorry I was involved in some in depth study on lightning about 35 years back (with regard to lightning protection/Telco gear).
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