Configuration and refinement of the RRFS system for operational implementation: aviation aspects of the deterministic and ensemble forecast components

NOAA’s Global Systems Laboratory (GSL) and Environmental Modeling Center (EMC) are working together toward the initial implementation of a new deterministic / ensemble regional prediction system. Known as the Rapid Refresh Forecast System (RRFS), this system will replace the High-Resolution Rapid Refresh (HRRR) and other current NCEP operational regional prediction systems, with a planned RRFS initial operational implementation in Spring of 2025. As with the HRRR, aviation applications (including convection, icing, turbulence, ceiling and visibility, etc.) are a focus for the RRFS model system and significant testing and evaluation of specific model and data assimilation components has been completed for the RRFS. These include specially adapted versions of the Thompson microphysics, Grell-Freitas (G-F) cumulus parameterization scheme, and MYNN boundary layer scheme, as well as an ensemble radar data assimilation procedure and scale-dependent / variable-dependent localization (SDL/VDL) procedure. This work is leading toward a final RRFS code freeze expected in Spring of 2024, followed by completion of final retrospective and real-time RRFS evaluations in Summer 2024.

Recent testing has focused on the G-F scheme and shown improvement from it in reducing a long-standing issue with overprediction of the most intense convective cores, resulting in a high bias for the highest thresholds of reflectivity and precipitation. At the conference, we will present results from this work, illustrating the improvement in the deterministic RRFS for convective systems and other weather phenomenon from the most recent model and data assimilation enhancements.

Additional RRFS work has focused on the ensemble prediction system, with evaluation of various scenarios for: inclusion of perturbed initial conditions, use of stochastic physics formulations, use of a multi-physics ensemble, and use of time-lagged ensembles from the RRFS (and potentially from the current operational HRRR, which will be maintained for some time after the initial RRFS implementation). At the conference, we will present comparison results (objective ensemble verification and subjective plots) from different RRFS ensemble formulations compared with the current High Resolution Ensemble Forecast (HREF) system. We will also discuss various RRFS ensemble use-case possibilities for aviation applications and asses the potential utility of the RRFS ensemble for quantifying uncertainty for aviation hazards.