Determining Causes for Modeled Mesoscale Convective System Dissipation Time Errors

While the prediction of mesoscale convective systems (MCSs) has generally improved with increased understanding of convective processes and advances in physical parameterizations and computational ability, the variability in these systems as well as the generally small spatial scale of convection makes them, particularly their dissipation, a forecasting challenge for numerical weather models. This research examines 40 MCSs that occurred between June and September from 2018-2021 over the eastern two-thirds of the Continental United States. All systems developed between 18 and 06 UTC, persisted nocturnally, and dissipated during the following 06-18 UTC time period. The dissipation time of each observed MCS was recorded and compared with that of the corresponding modeled MCS from the 06, 12, and 18 UTC runs of the High-Resolution Rapid Refresh (HRRR) Model. Overall, it was found that all three HRRR model run times tend toward a later MCS dissipation when compared to the observed dissipation time, though there is significant variance in the dissipation time for all three HRRR model run times. To further explore this issue, all 40 MCSs were simulated using the Weather Research and Forecasting (WRF) model to examine important environmental factors and mechanisms behind their dissipation, such as upper-level shear and mean wind, instability, strength and orientation of the low-level jet, and proximity to surface frontal boundaries, and discover any potential causes for discrepancies in dissipation times between the HRRR model and observations.