In March 2026, the Environmental Modeling Center (EMC) launched the “SFS Beta v1.0” Prototype. This SFS iteration generates monthly near-real-time (NRT) seasonal predictions up to 12 months and produces corresponding on-the-fly historical reforecasts spanning 1991-2025. Those reforecasts subsequently support forecast bias correction and seasonal forecast production (see CPC SFSbeta web page).

NRT & Reforecast Specifications The SFS Beta v1.0 employs CPC CORe (atmosphere) and GLORe (ocean/sea ice) initial conditions. It also utilizes land initialization from a Noah-MP land spin-up run forced by the CORe atmospheric forcing.

• Near-Real-Time (NRT) Component: Features a 31-member ensemble initialized at the start of each month, delivering a 12-month forecast by the 6th day of the NRT month.
• Reforecast Component: Provides a 30+ year historical baseline (starting in 1991) using 11 ensemble members initialized on the 1st day of the corresponding NRT month.

Integration and Open Data The SFSbeta in NRT will be integrated into the NMME forecast suites to inform operational seasonal outlooks at the CPC. Monthly atmospheric and oceanic reforecast and NRT data from SFSbeta will be made publicly available on the Cloud server (see SFS AT-hosted AWS Cloud).

This open-data approach enables the SFS development team to gather crucial feedback from CPC forecasters and the broader S2S research community, diagnose SFS model biases, and dynamically refine the system throughout its development cycle.

The SFS model integrates advanced physics and dynamics into its Earth system infrastructure, enhancing the coupled interactions between the land, ocean, sea ice, and atmosphere components.

The atmospheric physics package is largely based on the GFSv17 physics packages, featuring specific updates aimed to achieve improved computational efficiency and to better simulate large-scale climate variability across subseasonal and seasonal timescales. Key enhancements include:

• Dynamics: Replace the non-hydrostatic with the hydrostatic FV3 dynamical core to reduce computational costs.
• Gravity wave parameterization: Implementation of the ECMWF non-stationary gravity wave-drag parameterization to improve the representation of the Quasi-Biennial Oscillation (QBO) and polar stratospheric jets.
• Planetary boundary scheme: Adaptation of the Total Turbulence Energy EDMF PBL scheme.
• Aerosol forcings: Adoption of a 5-year sliding MERRA2 aerosol climatology to represent the historical trend of aerosol forcing.
• Deep convection: Improved prognostic convective closure to enhance Madden-Julian Oscillation (MJO) forecast skill.

In addition, ocean background gustiness was increased to reduce high-latitude SST bias. Parameters in SPPT and SKEB were tuned to improve ensemble spread. Further development of the SFSbeta will be focused on evaluating sensitivity of the system to ocean initial conditions and refining parameterizations to further reduce model systematic biases.

The SFS prototypes employ two specific reanalyses developed by the Climate Prediction Center (CPC) to initialize SFS experimental reforecasts. Please note the initialization strategy for the final operational SFSv1 will be different from what described below.

• GLORe (Global Ocean Reanalysis): Developed to replace the GODAS for ocean monitoring, GLORe utilizes a 1° resolution MOM6 ocean model with enhanced meridional resolution of 1/3° in the tropics and CICE6 sea ice model at a horizontal resolution of approximately 46 km. It is integrated via JEDI-SOCA 3DVar data assimilation on a 24-hour analysis cycle to support a reanalysis spanning from 1979 to the present, operating in near-real-time with a two-day latency.
• CORe (Conventional Observation Reanalysis): Replacing the NCEP/NCAR Reanalysis 1 for climate monitoring, CORe employs an FV3GFS15 dynamical core (C128 ≅ 0.7° resolution) with 64 vertical levels. It uses an 80-member Ensemble Kalman Filter on a 3-hour analysis cycle—assimilating conventional data only—to generate a 1950-present atmospheric reanalysis. CORe was implemented operationally on March 19, 2026 (see CPC CORe web page).

SFS Prototypes and Reforecast Experiments The primary experimental reforecasts span a 30-year hindcast period (1994-2023) and are initialized on May 1st and November 1st for each year in that period. Data generated from these four prototypes is hosted on the SFS AT-hosted AWS Cloud.