[1] Horizontal and line-normal, vertical cross-sections and composite images of Dallas-Fort Worth Lightning Detection and Ranging (LDAR II) VHF radiation sources and radar reflectivity over a 30-min period provide a unique perspective on lightning pathways within a leading-line, trailing-stratiform (LLTS) mesoscale convective system (MCS) on 16 June 2002. The overwhelming majority of VHF lightning sources occurred within the leading convective line in a bimodal pattern in the vertical. Assuming that VHF source density maxima were most likely associated with positive charge, then the LDAR II observations suggest that the gross charge structure of the convective region of the MCS was characterized by a tripole with net positive charge centered at 4.5 km AGL (3°C) and 9.5 km AGL (À35°C) and net negative charge centered roughly in the relative minimum of the VHF source density maximum at 7 km AGL (À17°C). A persistent lightning pathway and inferred positive charge zone sloped rearward (by 40-50 km) and downward (by 4-5 km) from the upper VHF source maximum in the convective line, through the transition zone, and into the radar bright band of the stratiform region. In the stratiform region, VHF lightning sources and inferred positive charge were concentrated in three layers centered at 4.5, 6, and 9 km AGL (2°C, À11°C, and À31°C, respectively), consistent with past electric field studies of symmetric LLTS MCSs. Positive cloud-to-ground lightning flashes in the stratiform region were initiated in the convective line and followed the slanting pathway from the top of convective cores to the stratiform precipitation, where they were horizontally extensive, layered, and highly branched. The sloping lightning pathway was identical to hypothetical trajectories taken by snow particles. These observations provide further support for the advection of charge on snow along the sloping pathway and the in situ generation of charge in the horizontal lightning layers as primary contributors to electrification and positive lightning production rearward of the convective line.

A multi-sensor study of the leading-line, trailing-stratiform (LLTS) mesoscale convective system (MCS) that developed over Texas in the afternoon of 7 April 2002 is presented. The analysis relies mainly on operationally available data sources such as GOES East satellite imagery, WSR-88D radar data and NLDN cloud-to-ground flash data. In addition, total lightning information in three dimensions from the LDAR II network in the Dallas-Ft. Worth region is used.GOES East satellite imagery revealed several ring-like cloud top structures with a diameter of about 100 km during MCS formation. The Throckmorton tornadic supercell, which had formed just ahead of the developing linear MCS, was characterized by a high CG+ percentage below a V-shaped cloud top overshoot north of the tornado swath. There were indications of the presence of a tilted 0169-8095/$ -see front matter D electrical dipole in this storm. Also this supercell had low average CGÀ first stroke currents and flash multiplicities. Interestingly, especially the average CG+ flash multiplicity in the Throckmorton storm showed oscillations with an estimated period of about 15 min.Later on, in the mature LLTS MCS, the radar versus lightning activity comparison revealed two dominant discharge regions at the back of the convective leading edge and a gentle descent of the upper intracloud lightning region into the trailing stratiform region, apparently coupled to hydrometeor sedimentation. There was evidence for an inverted dipole in the stratiform region of the LLTS MCS, and CG+ flashes from the stratiform region had high first return stroke peak currents. D