Explicit electrification and lightning forecasts in the WRF-ARW model

Lightning threats in present-day numerical weather prediction models are currently diagnosed from model variables such as graupel mixing ratio and ice water content that are known to be well correlated with the occurrence of lightning. To provide a more physically sound assessment of lightning threat, an explicit charging/discharge model (with explicit elliptic solution of the 3D component of the ambient electric field) has been successfully implemented into the NSSL two-moment microphysics scheme within the WRF-ARW model. Preliminary results from cloud-scale (2-km) simulations of Hurricane Rita and a continental severe weather outbreak case will be presented. The electrical evolution of the simulated hurricane exhibits traits in good agreement with observations. The gross charge structure in the eyewall is a tilted normal-polarity tripole resulting from negative (positive) non-inductive charging of graupel (cloud ice/snow) at midlevels (upper levels) and positive non-inductive charging of cloud water at lower levels. The largest flash density rates during the rapid intensification period are in the eyewall, with a weak secondary maximum in the rainbands.