Electrification and Lightning in Simulations of the 29 May 2004 Geary, OK Storm Using EnKF Data Assimilation

On 29 May 2004, a line of convective cells formed along a dryline near Elk City, OK; one intensified to a heavy-precipitation (HP) supercell north of Weatherford, OK as it moved into the TELEX domain (MacGorman et al. 2008). The data set established through this field campaign provides an excellent opportunity for using Ensemble Kalman Filter (EnKF) assimilation of radar data to produce a storm simulation having characteristics similar to those of the observed storm, so that we can examine hypotheses concerning the storm's electrification and lightning.

The Collaborative Model for Multiscale Atmospheric Simulation (COMMAS) was used to produce the simulations. Radial velocity and reflectivity data from a single mobile doppler radar were assimilated into the the COMMAS model using two-moment microphysics, including seven hydrometeor categories, and parameterizations for electrification and lightning with a horizontally homogeneous base state. The simulated precipitation and wind fields were similar to those of the observed storm. Simulated lightning flash rates were very large, as was observed, and the distribution of charge in the main body of the storm revealed in the simulation details the lightning dependence on storm kinematics that could not be directly observed. The simulation produced the observed lightning holes and the high-altitude lightning seen in the observations. However, the simulation failed to produce the observed lightning initiations (or even lightning channels) in the distant downstream anvil; instead, the simulated lightning was confined to the main body of the storm.