Date: Friday 15th May 2015
Time: 04:40-06:30 Local
Location: Norman, Oklahoma. USA.
Path: Overhead

Rearward sloping cold front with MCS
Duration: about 2 hours
Type: Rearward sloping Multicell Squall line
Average lightning type: CG/GC and Anvil Crawlers
Footage Quality: Full HD / DSLR


An early morning squall line approached Norman Oklahoma in the early hours of the 15th May 2015 whilst I was working over there, so I set my cameras up against the hotel window for some potential lightning shots (albeit through a triple-glazed window - so a bit of ghosting on images). The clicking noise you hear in the video is the lightning trigger on my accompanying DSLR.

This was a classic example of a rearward-sloping squall line, a linear storm-mode thunderstorm covering hundreds of miles progressing slowly eastwards across Oklahoma. The most intense part of the storm was along the cold front, itself whereby ahead of this, warm humid air travelled northwards with low cloud and "silent" lightning of increasing frequency, then the squall hit with torrential rain and negative C-G lightning.

Then, a clearance to the cold air and a backward sloping anvil. The latter is a lightning photographer's playground, as the discharges are large and pretty (Anvil Crawlers and Ground to Clouds), whilst receiving a clear view of the show in the colder, drier airmass, often without much rain.

A distant radio mast got struck (or more accurately, IT struck the cloud) 5 times upon the storm's departure with Ground to Cloud lightning, often spraying into an Anvil Crawler.

A possible rare bi-polar stroke at 3:41​ in the video was captured, where the initially positive channel seems to get reused by one of the branches from a possible negative region.

Storms like this rarely happen in the UK, especially as intense and large-scale as this, as the airmass structure and properties are different in the US, and unachievable without living in a big well-mixed continental airmass. We can sometimes see these rearward slopers in Spanish Plume events, but more often than not they forward-slope.

Here is the radio mast that kept releasing lightning this night...

& SFERICS (Credits)



Mark Seltzer  www.electricsky.co.uk


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