The High Resolution Rapid Refresh (HRRR): Recent enhancements and evaluation during the 2009 convective season

For the 2009 convective season, the 3-km High Resolution Rapid Refresh (HRRR) was run over an expanded domain covering the eastern 2/3 of the United States. Real-time hourly forecasts out to 12-h were produced and a variety of convective guidance products were produced (including 15-min VIL output fields and tracks of severe weather indicators). The HRRR is initialized from the hourly updating Rapid Update Cycle (RUC), and benefits from the RUC data assimilation system, including a radar reflectivity assimilation procedure to initialize ongoing precipitation systems. The RUC radar reflectivity assimilation procedure (Weygandt et al, this conference) uses a diabatic digital filter (DFI) initialization to generate storm scale circulations in regions of ongoing convection and has significantly improved short-range precipitation forecasts (especially for convective systems) in both the RUC and HRRR.

During the summer of 2009, output from the HRRR was used as input to the Collaborative Storm Prediction for Aviation (CoSPA), a convective guidance product produced jointly by ESRL/GSD, NCAR/RAL, and MIT/LL. Within CoSPA, HRRR forecast fields were combined with radar nowcast fields to provide a seamless 0 to 8-hr convective guidance product, which was evaluated for aviation planning purposes. HRRR guidance was also evaluated as part of the 2009 SPC/NSSL spring experiment and was used to provide severe weather guidance by VORTEX2 field experiment leaders. In addition, time-lagged ensemble output from the HRRR was used as input to create a new convective probability guidance product, known as the HRRR connective Probability Forecast (HCPF, Alexander et al, this conference).

At the conference, we will provide an overview of the enhancements to the HRRR for the 2009 season and provide statistical assessments and case study examples to illustrate the forecast performance of the HRRR. Finally, we will describe plans for 2010.