Impact of Targeted Afternoon Radiosonde Observations on Convection-Permitting Forecasts of the 31 May 2013 Convective Event in Oklahoma

Recent studies have examined the interaction of deep convection with the surrounding environment with numerical weather prediction model forecasts that assimilate surface and radar data. However, the impact of assimilation of targeted radiosonde observations in pre-convective environments on 0-6 hour convection-permitting model forecasts has not yet been explored. The EF5 El Reno tornado and the associated convection on May 31, 2013 was one of the high impact events sampled by the Mesoscale Predictability Experiment (MPEX). Standard radiosonde, aircraft, and surface observations will be assimilated every hour from 0000-1600 UTC using an Ensemble Kalman filter method within a Weather Research and Forecasting (WRF) model mesoscale ensemble (18 km grid spacing). Three targeted radiosonde observations and a special 1800 UTC National Weather Service sounding will be assimilated from 1600 to 2000 UTC. Two of these soundings were obtained by MPEX near Norman, OK (1610 UTC) and Chickasha, OK (1920 UTC). The other was obtained by a team from the State University of New York at Oswego at 1800 UTC near Stillwater, OK. A convection-permitting grid will be embedded at 2000 UTC, and an ensemble of forecasts will run out to 6 hours. This same method will be repeated without assimilation of MPEX data, and again in intermediate trials using only one or two soundings. The impact of the targeted radiosonde observations will be evaluated by quantifying the accuracy of the timing and location of convective initiation, the tornadic supercell near El Reno, and the transition to a heavy-rain/high-wind producing Mesoscale Convective System (MCS).