Researchers at the National Severe Storms Laboratory (NSSL) have been running an experimental version of the Eta model for several years to compliment operational runs of the Eta at the National Centers for Environmental Prediction (NCEP). The primary difference between these models runs is the convective parameterization schemes used in their configuration. The operational Eta model uses the Betts-Miller-Janjic (BMJ) scheme while the locally run experimental version uses a Kain-Fritsch (KF) scheme (called EtaKF). An evaluation and subjective verification of convective forecasts and other parameters associated with these models has been conducted as part of the SPC/NSSL Spring Program for several years.

During model evaluation and verification, empirical observations noted distinct characteristics of the Eta and EtaKF in the forecasts of mesoscale convective systems (MCS) during the warm season. A study to examine characteristics of MCS initiation and evolution during 2000 and 2001 based on Eta and EtaKF forecasts was conducted. Results from eight MCS cases demonstrate the utility of the Eta and EtaKF in predicting the initiation and progression of MCS during the period. Systematic biases observed in forecasts from each model provide key insight into the impact these different convective parameterization schemes have on forecasting MCS initiation and progression within the Eta model framework. In addition, EtaKF forecasts were examined in detail concerning the partitioning of grid-resolved and parameterized precipitation, as well as the relationship between EtaKF maximum updraft mass flux values and vertically integrated liquid values from radar. Research results and potential forecast applications will be presented and discussed.