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Radio images of 26 consecutive lightning flashes are described in relation to radar pictures of the storm. These flashes all started in two vertical turrets where reflectivity factors exceeded 25 dBZ. Five large cloud flashes pervaded an almost horizontal plume or low-level anvil, and ground flashes occurred on the opposite side, in the propagating flank of this storm. Observers on the ground reported a light hailfall and copious rain. Most of the lightning occurred in a region that was 3--5 km above ground (AGL). Flashes originated at heights that ranged from 3.1 km (where the environmental air temperature was -5 ¿C) to 5.1 km AGL (-16¿C) and they began at a mean height of 3.94 km AGL (-10 ¿C). The standard deviation of 26 heights at which flashes began was 440 m. Recorded electric field-changes showed that the channels were charged negatively, and we inferred that negative charge had accumulated at these heights in the vertical turrets, and that the paths followed by cloud flashes were influenced by positive charge which had accumulated in a plume that was nearly horizontal and which had formed on the flank opposite to the propagating flank of the storm. The estimated total length of 18 consecutive lightning flashes that had occurred during a 3-min interval was 486 km. Measurements of electric field-change magnitudes were used to estimate totals of 440 C and 106 C that had been discharged in 180 s from two cells whose volumes (enclosed by 30 dBZ surfaces) were 260 and 80 km3, respectively. This paper also describes the geometries of stepped leaders that cause electric field-changes of the BIL form. It discusses a continuing current which was carried by a cloud flash. |