Model estimates of lightning in convective systems in southern Mexico and the Gulf of Tehuantepc

Convection in southern Mexico during the rainy season can lead to extreme precipitation and flooding. Often, precipitation events lead to landslides and loss of properties and lives in this mountainous region. Convective systems can be the result of synotic scale forcing in the tropics (e.g. easterly waves) and can be either precursors of tropical systems or remnants of landfalling tropical depressions/storms. Three case studies of extreme precipitation observed in 2008 were selected to evaluate their lightning potential. The systems were simulated with the Weather Research and Forecast (WRF) model, at high resolution (3 and 1 km horizontal spacing). Lightning flash rates were determined for a variety of proxies, calculated from the modeled values and compared against observations made with the Worldwide Lightning Location Network (WWLLN). Six model parameters were calculated: precipitation ice mass, ice water path, updraft volume, cloud top height, maximum vertical velocity (Barthe et al., 2010), and lightning potential index (LPI, Yair et al. 2010). Note that the cited studies pertain to mid-latitude convective storms. The results show that the observed flash rate is best described by the maximum vertical velocity parameter and the LPI. High correlations were found between the simulated precipitation and the LPI as well as the maximum vertical velocity, in one of the simulated cases (3-6 June 2008). It is worth noting that neither cloud top height nor ice water path were useful as proxy for lightning, since the threshold for reflectivity was never reached in the simulations of these tropical systems.