Comparing the NSSL-WRF Model and Convection-allowing Versions of UKMET's Unified Model during the 2013 and 2014 NOAA/HWT Spring Forecasting Experiments
To gauge the quality of the convection-allowing UM forecasts, daily subjective comparisons of simulated reflectivity were made to the 4-km grid-spacing NSSL-WRF and corresponding observations. The NSSL-WRF is a real-time modeling framework that has been used to provide storm-scale guidance to SPC forecasters since 2006 and is generally highly regarded. Thus, the NSSL-WRF serves as a useful baseline against which to compare the UM forecasts. In addition, forecast soundings from the NSSL-WRF and UM were compared.
Overall, the UM compared very favorably to the NSSL-WRF. In fact, for the majority of the HWT/SFE cases during 2013 and 2014, the UM was rated subjectively as better than the NSSL-WRF. Also, a striking difference between the NSSL-WRF and UM was noticed for forecast vertical profiles of temperature and moisture when capping inversions were present. The UM oftentimes very accurately depicted the sharp gradients in temperature and moisture observed at the interface of the boundary layer and elevated mixed layer, while the NSSL-WRF and other high-resolution WRF model simulations in general predicted more smoothed temperature/moisture gradients and weaker inversions at this interface. This poster will present a summary of results from the Met Office and NSSL/SPC collaboration, as well as show examples of the different forecasts of simulated reflectivity and boundary layer profiles from the NSSL-WRF and UM.