Progress in High-Resolution Rapid Refresh (HRRR) Deterministic and Ensemble Development for Convective Hazard Forecasts

Development of the Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) model forecast systems started a little more than a decade ago. These models were designed with community-based components including Gridpoint Statistical Interpolation (GSI) for observational data assimilation, a specially configured version of the Advanced Research WRF (ARW) model, and unified post-processing (UPP).

With the adoption of community-supported model components such as GSI, WRF-ARW and UPP, frequent contributions to the RAP and HRRR development have been possible, and as such, a more agile model development paradigm has been established with rapid prototyping for evolutionary upgrades to the RAP and HRRR including use of real-time experimental forecasts that permit operational forecaster feedback. This paradigm and close coordination with the National Center for Environmental Prediction (NCEP) Environmental Modeling Center (EMC) has facilitated a two-year research-to-operations (R2O) transition cycle for the RAP/HRRR between their operational inceptions in 2012/14 and present. We have now concluded the third and fourth R2O cycles of the HRRR and RAP respectively with another transition cycle planned for completion by mid-2020 that will include a HRRR storm-scale ensemble analysis capability, and eventually, ensemble prediction.

This presentation will review highlights of the RAP/HRRR and HRRR ensemble development including a look towards 2020 and eventual incorporation in an operational unified rapid refresh forecast system by 2022. Forecast skill improvements related to specific enhancements in RAP/HRRR WRF-ARW numerics, physical parameterizations and associated data assimilation in the 2018 and 2020 packages with be presented with a focus on convective hazards.