2010 results from the 3km HRRR - verification, case study assessment, and HRRR-based convective probabilistic forecasts (HCPF)

The High Resolution Rapid Refresh (HRRR) is a 3-km, convection resolving model, run hourly in real-time at the Global System Division (GSD) of the NOAA Earth System Research Laboratory (ESRL). The WRF-ARW-based HRRR is run out to fifteen hours over a domain covering the entire continental United States (CONUS), using initial and boundary conditions from the Rapid Update Cycle (RUC). The HRRR has also been initialized from the Rapid Refresh (RR). The RUC and RR include a diabatic digital filter-based radar reflectivity data assimilation procedure to initialize areas of precipitation. HRRR gridded output is used as input to a convective guidance product known as the Collaborative Storm Prediction for Aviation (CoSPA). In addition, a logistic regression-based time-lagged ensemble procedure is used to create probabilistic thunderstorm guidance from the HRRR. During the summer of 2010, a real-time evaluation of the use of CoSPA to aid aviation traffic management was conducted in conjunction with the FAA. During this period, GSD conducted an in-house assessment of the HRRR. This assessment included scale-dependent verification, case-study analysis and evaluation of the HCPF probabilities.

In this presentation, we will show results from the assessment, highlighting the diurnal, forecast length, and scale dependencies in both the HRRR and HCPF verification. Case study analysis will focus on specific deficiencies seen in the HRRR forecasts, including difficulties maintaining realistic MCS structures and MCS propagation speed. In addition, a diurnal bias tendency based on the initial time of the HRRR forecast (increasing amounts of convection for successive HRRR runs) will be discussed. Based on this analysis, retrospective case-study model experiments are being conducted to address these and other forecast deficiencies and to examine the impact from changes to the radar assimilation procedure within the RUC/RR. We will describe these and discuss planned enhancements for the HRRR system.