Impact of Lightning Data Assimilation on High-Resolution Numerical Forecasts of the 29 June 2012 Derecho

The 29 June 2012 derecho produced widespread wind damage across the Ohio River Valley. The event proved to be difficult to forecast given that global and mesoscale operational models failed to produce a significant MCS even just 12 hours in advance. Here the impact of the assimilation of lightning data on a convection-allowing, high-resolution (3km) deterministic forecast of the event is evaluated using the WRF-ARW model. Assimilation is performed using Newtonian nudging of water vapor mixing ratio values throughout the troposphere in order to initiate convection near the location of lightning strikes. The lightning strike location information is provided by the Worldwide Lightning Location Network (WWLLN). The performance of the assimilation scheme is evaluated in the context of the high-impact features of the event, using surface wind and rainfall observations. The simulations are repeated, confining the nudging of water vapor mixing ratio values to the mixed phase region. The results from these simulations are presented.