Lightning in a Florida "pulse" storm: Positive and negative leaders are represented by the yellow and white contours, respectively. Thus, white leaders to ground indicate -CG flashes. The red diamonds indicate where lightning was initiated in the model. Each frame shows 2 minutes of lightning activity. The brown surfaces are mixing ratio of precipitation greater than 1 g/kg, whereas light gray and blue-gray indicate the cloud boundary (small droplets and ice crystals, respectively). The surface color contour shows reflectivity from weak (blue) to strong (red). The view is from the south.

This simulation used the Saunders et al. (1991) noninductive charging parameterization, with modifications to the low liquid water content charging zones as in Helsdon et al. (2001). There was no inductive charging, but a minimum ice crystal concentration up to 100 per liter. Results are quite similar with the Gardiner/Ziegler noninductive charge separation parameterization. Unlike the multicell case, here a lower postive charge (LPC) region develops immediately because of the warm rain process. The initial precipitation is rain that forms before the updraft reaches the freezing level. After the drops freeze, they rime into small hail and high density graupel. This provides ice particles right away at relatively high temperatures where graupel charges positively by the noninductive process. The negative electric fields (Ez) at the surface reflect the strong LPC from the outset. The LPC is involved in IC and -CG flashes, both of which have downward negative leaders and upward positive leaders.

The simulation used the 1810Z TCO sounding from 9 August 1991 during the CaPE field program. The horizontal and vertical resolutions are 250 m.