Multiple Strokes Along the Same Channel to Ground in Positive Lightning Produced by a Supercell

Previous studies have shown that subsequent leaders in positive cloud-to-ground lightning (+CG) flashes rarely traverse pre-existing channels to ground. In this paper, we present evidence that this actually can be common, at least for some thunderstorms. Observations of +CG flashes in a supercell storm in Argentina by Cordoba Argentina Marx Meter Array (CAMMA) are presented, in which 54 (64%) of 84 multiple-stroke +CG flashes had subsequent leaders following a pre-existing channel to ground. These subsequent positive leaders are found to behave similarly to their negative counterparts, including propagation speeds along pre-existing channels with a median of 8 x 10(6) m/s, which is comparable to that of negative dart leaders. Two representative multiple-stroke +CG flashes are presented and discussed in detail. The observations reported herein call for an update to the traditional explanation of the disparity between positive and negative lightning. Plain Language Summary Despite the fact that positive lightning is more energetic and more likely to result in severe damage than negative lightning, it remains much less understood than its negative counterpart. We report on a totally unexpected behavior of positive lightning produced by a supercell thunderstorm in Argentina. Specifically, the observed positive lightning flashes were composed of multiple strokes retracing the same channel to ground, which differs from the expectation that positive lightning rarely delivers charge to the same place on the ground in a discrete manner. Our observations show that the behavior of subsequent leaders in positive lightning can be very similar to that of subsequent leaders in negative lightning. Our findings call for a change to our current understanding of positive lightning.