An uncommon three‐stroke positive cloud‐to‐ground (+CG) lightning flash was observed by synchronous multifrequency radiation sensors, and the three‐dimensional development of the channel was carefully mapped. Results show that three positive strokes grounded at different points approximately 4–8 km apart and time intervals between neighboring +CG strokes were 85 and 222 ms, respectively. This +CG flash was preceded by an intracloud (IC) discharge. The locations of the termination points on the ground were just below the preestablished horizontal IC discharge channels, and the three strokes were linked with each other through sharing horizontal negative leader channels inside the cloud. There were stepping pulses less than 0.4 ms before the first and second return strokes (RSs), and their location results were distributed nearby the following RS, indicating that the pulses might be associated with the attachment process. The first and second positive strokes occurred when the horizontal in‐cloud negative channel stopped extending, while the third positive stroke occurred below the opposite end of an advancing negative leader in the cloud. The above results suggest that the downward positive leader preceding the strokes possibly developed either from different decayed leader channels or from the opposite end of an advancing leader channel. A high‐speed camera captured a downward positive attempted leader from another +CG flash, revealing how a downward positive leader incepted from a horizontal negative lightning channel.

Fine time‐resolved images of the development of lightning bidirectional leaders below the cloud base were captured by a high‐speed camera in association with multiband electromagnetic field measurements. The bileaders tended to originate at a radial distance of about 200 m from a progressing positive leader channel, propagating more or less radially toward and away from the main channel. Significant asymmetrical channel extensions at opposite ends were clearly recognized. The positive ends of the bileaders propagated in single paths with average speed of 6.1 × 10⁴ m/s, while the opposite negative end involved obvious branching and stepping propagation with average speed of 1.6 × 10⁵ m/s. The bidirectional leaders eventually connected to the existing main positive leader, producing new branches of the flash. Another cause of positive leader branching was that the positive leader split at its head and developed into different branches synchronously, which were sometimes invisible but were revealed by recoil leaders.

We identify and investigate the intermittent propagation of upward positive and negative leaders in rocket‐triggered lightning based on comprehensive observations of fine time‐resolved optical, current, and electromagnetic fields. There is an abrupt luminous crown blooming due to the achievement of a positive leader step, after which the channel weakens and the head degrades. During the positive leader pausing, residual structure is recognized at area of previous luminous crown blooming, in the form of a floating segment. Our observation point to a possible mechanism that it connects with the positive leader head, causing a forward‐step and a sharp current pulse. This is to some extent similar to negative leader stepping, in which the space leader emerges and connection between the space leader and the channel head occurs. The generation of clustered space leaders give rise to negative channel branching, but the residual structure in positive leader just leads to individual step.