An M component with a concurrent dart leader traveling along different paths during a lightning flash

Utilizing time‐correlated high‐speed video and electric field change data, a seven‐stroke lightning flash is described in which the fifth return stroke (RS) occurs 0.80 ms after the fourth RS connects to a different ground location 3.3 km away. The fifth RS is 0.34 ms after an M component starts down the different channel. The fifth stroke involves a dart leader traveling concurrently, though slower than the M component, in a prior channel to ground. There was no indication of leader advance along this path earlier during the fourth RS. The fourth stroke involves a stepped leader that started from the end of an observed prior dart leader branch which did not previously propagate to ground. The concurrent M component and dart leader are preceded by an in‐cloud event evidenced by a large‐amplitude, fast electric field change pulse, at 6.1 km estimated altitude, inferred as the connection to the channel for the M component. The M component current apparently initiates the dart leader about 40 µs later. A visible channel length of 10,400 m allows for the 2‐D propagation speed of the M component luminosity to be estimated in the range of 1.0 to 1.2 × 10 8  m s −1 . The concurrent dart leader travels a visible length of 3445 m with 2‐D speed of 1.7 × 10 7  m s −1 , similar to other dart leaders in this flash. Luminosity evolution along the channel through the RS and M component is also described. Estimated optical risetimes of three separate M components are 80–200 µs at 520 m above ground.