The Thunderstorm Electrification and Lightning Experiment (TELEX) observed a high-precipitation tornadic supercell storm on 29 May 2004. The available observation systems included the Oklahoma Lightning Mapping Array (LMA), the KOUN S-Band polarimetric radar, and two mobile SMART-R C-Band radars. Thunderstorm charge is thought to be produced by microphysical interactions between graupel and cloud ice followed by differential sedimentation to produce regions of net charge. If so, the kinematics of the storm govern spatial relationships between regions of microphysical charging and the location and geometry of those charge regions.

On 29 May 2004, lightning flashes near the core of this storm, although quite frequent, tended to have shorter duration and smaller horizontal extent than typical flashes in other storms having less frequent lightning. We suggest that this is due, at least in part, to small pockets of opposite charge lying in close proximity to each other. Thus, each polarity of lightning leader propagates only a relatively short distance before reaching regions of unfavorable electrical potential. In the anvil, however, lightning extended tens of kilometers from the reflectivity cores in roughly horizontal layers, consistent with the charge spreading through the anvil in broad sheets. Though lightning has been previously observed in anvils, typically this lightning is initiated in or near the core of the storm and extends out into the anvil. Yet, in the 29 May 2004 storm, flashes initiated in the anvil region and the subsequent leaders progressed back towards the core of the storm. Some of these flashes were negative cloud-to-ground flashes that initiated over 50 km away from the core and struck ground beneath the anvil close to the initiation point. We hypothesize that interaction between the anvil of this supercell and a somewhat lower anvil of opposite polarity from a weaker left-moving cell to the north was responsible for initiating this lightning.