The Relationship between Cloud-to-Ground Lightning Polarity and Surface Equivalent Potential Temperature during Three Tornadic Outbreaks

Abstract

Abstract The relationship between cloud-to-ground (CG) lightning polarity and surface equivalent potential temperature (θe) is examined for the 26 April 1991, Andover–Wichita, Kansas; the 13 March 1990, Hesston, Kansas; and the 28 August 1990, Plainfield, Illinois, tornadic storm events. The majority of thunderstorms whose CG lightning activity was dominated by negative flashes (labeled negative storms) formed in regions of weak θe gradient and downstream of a θe maximum. The majority of thunderstorms whose initial CG lightning activity was dominated by positive flashes formed in regions of strong θe gradient, upstream of a θe maximum. Some of these storms moved adjacent to the θe maximum and were dominated by positive CG lightning throughout their lifetimes (labeled “positive storms”). The other initially positive storms moved through the θe maximum where their updrafts appeared to undergo intensification. The storms’ dominant CG polarity switched from positive to negative after they crossed the θe maxim...