Activities and Preliminary Results from the 1st Hybrid NOAA/Hazardous Weather Testbed Spring Forecasting Experiment

The 2023 Spring Forecasting Experiment (2023 SFE) was conducted from 1 May – 2 June 2023 by the Experimental Forecast Program (EFP) of the NOAA/Hazardous Weather Testbed (HWT), and co-led by the NWS/Storm Prediction Center (SPC) and OAR/National Severe Storms Laboratory (NSSL). After three years of virtual experiments, this was the first experiment with in-person participation since 2019. Additionally, we continued with virtual participation in the 2023 SFE, making it the first hybrid experiment. The 2023 SFE featured experimental model contributions from NOAA/OAR Global Systems Laboratory (GSL), NOAA/NCEP Environmental Modeling Center (EMC), NOAA/OAR Geophysical Fluid Dynamics Laboratory (GFDL), NOAA/OAR National Severe Storms Laboratory (NSSL), the Global Modeling and Assimilation Office of NASA/Goddard Space Flight Center, and the National Center for Atmospheric Research. With tentative plans for operational implementation of the Rapid Refresh Forecast System (RRFS) in early 2025, an important emphasis of SFE 2023 was RRFS evaluations against the operational High-Resolution Rapid Refresh (HRRR) and High-Resolution Ensemble Forecast (HREF) systems for severe weather forecasting applications. New testing and evaluation activities for SFE 2023 included examinations of regional and global-with-nest versions of the Model for Prediction Across Scales (MPAS), and new extended range (Days 3-8) CAM ensemble evaluations were also conducted. Experimental forecasting activities involved generation of severe weather outlooks at Days 1-4, and short-term forecasting activities centered around NSSL’s prototype Warn-on-Forecast System (WoFS).

Preliminary results generally show that while progress is being made with RRFS, performance for severe weather forecasting applications is still lagging behind HREF and HRRR. Several improvements with regard to RRFS model and ensemble configuration are being actively explored before a code freeze scheduled for April 2024.

Initial testing of NCAR’s MPAS model during the 2023 SFE was motivated by NSSL’s Warn-on-Forecast initiative, which aims to extend warning lead times for severe weather hazards using an on-demand, adaptable domain and a rapidly updating high-resolution ensemble analysis and forecast system. The current prototype of WoFS uses the Advanced Research WRF (ARW) configuration of the Weather Research and Forecasting model. However, NSSL has begun exploring alternative model cores for a next-generation version of WoFS that would (1) accommodate further refinements in grid-spacing (i.e., 1-km), (2) accommodate advances in data assimilation, and (3) fit within the framework of NOAA’s Unified Forecast System (UFS) initiative. Tests with the Finite Volume Cubed Sphere model (FV3) consistently yielded spurious storms at model initialization, inability to recover from early imbalances, and unrealistic storm characteristics. Thus, in collaboration with NCAR, NSSL has begun to explore MPAS for its next-generation WoFS. The first step in this process was testing the model at “Day 1” lead times (i.e., 12-36h forecasts) during the 2023 SFE to assess performance characteristics relative to the current operational baseline of the HRRR and future baseline of RRFS. For these tests, three CONUS-domain, 3-km grid-spacing MPAS configurations were developed at NSSL: (1) MPAS HT, (2) MPAS HN, and (3) MPAS RT. In these names, the last two letters denote the initialization dataset and microphysics scheme, respectively. “HT” is HRRR/Thompson, “HN” is HRRR/NSSL, and “RT” is RRFS/Thompson. Preliminary results showed that the MPAS configurations performed very well and 0000 UTC initialized MPAS HN subjective ratings approached those of the HRRR during the Day 1 period. Additionally, MPAS RT outperformed the RRFS from which it was initialized. RRFS had major issues with storms that were too intense and spurious convection, which was most apparent at initialization, diurnal peak, and the uncapped warm sector in weakly forced environments. This talk will summarize 2023 SFE activities and highlight some of these preliminary results.