Cloud-to-ground lightning throughout the lifetime of a severe storm systemin Oklahoma

Cloud-to-ground (CG) lightning data are examined relative to digitized rada r data for a storm system that occurred in Oklahoma on 26 May 1985. This sy stem evolved through three stages: 1) two lines of cells, one near the dryl ine and the other 60 km ahead of it; 2) a supercell storm; and 3) a mesosca le convective system (MCS). The behavior of lightning in each stage was dif ferent. Initially no ground Bashes were observed in either line until refle ctivity increased to greater than or equal to 46 dBZ and vertically integra ted liquid (VIL) increased to greater than or equal to 10 kg m(-2); then gr ound Bash rates remained <1.2 min(-1) for >1 h. Most ground flashes in the line of storms near the dryline were negative (18 -CG, 3 +CG), while most i n the leading line were positive (11 +CG, 3 -CG), a pattern of polarity opp osite to what usually has been observed. Approximately 3 h after radar dete cted the first storm, ground flash rates increased to >5 min(-1) and remain ed so for 6 h. A mesocyclone formed approximately 30 min after flash rates exceeded 5 min(-1), and a few positive ground Rashes occurred near it. Grou nd flash rates increased briefly to >20 min(-1) as the mesocyclone dissipat ed and then remained >10 min(-1) as a squall line formed along the outflow boundary from the dissipating supercell and produced a stratiform region. M ost ground Rashes in this MCS occurred in the convective line and had negat ive polarity. The few ground flashes in the stratiform region tended to be positive (42 +CG, 32 -CG during 3 h). During 1 h of the MCS, ground Bash ra tes decreased and then increased again simultaneously in both the convectiv e and stratiform regions, a previously undocumented behavior. It is possibl e that this was caused by updrafts in both the convective line and stratifo rm region changing at roughly the same time. It is also possible that most ground flashes in the stratiform region originated near the convective line , and so were influenced by the line. Overall trends in ground flash densit y, flash relative frequency, reflectivity, VIL, and severe hail reports app eared similar as the storm system evolved.