An Evaluation of the Impact of Increased Horizontal Grid Spacing on SREF Performance

The Developmental Testbed Center (DTC) Ensemble team has performed testing to evaluate the impact of increasing the horizontal grid spacing from 16km to 9 km for the National Center for Environmental Prediction/Environmental Modeling Center (NCEP/EMC) Short-Range Ensemble Forecast (SREF) system. The current test is focused on the WRF-ARW SREF members. The ensemble consists of seven members including a control member and two pairs of three members with a negative and corresponding positive breeding initial condition perturbations. This preliminary study was performed over the transition month of May 2013 and captured one of the most active severe weather months in recent history hence providing an interesting dataset for future in-depth studies. Verification was performed using the DTC's Model Evaluation Tools (MET). This talk will focus on the ARW SREF members performance at 9km and 16 km using both single-value and probabilistic measures aggregated over the entire month of study.