High-Speed Video And VHF LMA Observations Of M-Components In A Single-Stroke Negative CG Flash With Very Long Continuing Current

On May 7, 2008 we obtained high-speed, 10,000 frame per second, video and VHF radiation source location data from the Oklahoma Lightning Mapping Array (OK-LMA) for a single-stroke negative cloud-to-ground flash with a continuing current that lasted approximately 700 milliseconds. During the first 300 milliseconds of the continuing current there were 14 M-components recorded in the high-speed video. We have examined the OK-LMA data during the long continuing current to elicit any patterns that might be related to the occurrence of the M-components. For example, we thought there might be a burst of activity in the OK-LMA data just before each M-component. Contrary to our expectations, there is an apparent lack of specific temporal or spatial patterns in the occurrence of VHF source locations in relation to the M-components. However, the VHF source locations occur at increasing distances, mostly horizontally, from the ground-strike location during the continuing-current interval.