Unified Forecast System

Table of Contents

1) Latest News

March 4, 2021 : UFS Short-Range Weather Application v1.0 is now available. For details, please visit the UFS community web site on this release.

October 6, 2020 : UFS Medium Range Weather Application v1.1 is now available. For details, please visit the UFS community web site on this release.

July 2020: Launch of UFS Research to Operations (UFS-R2O) Project. For details, please visit the UFS-R2O web site.

The first UFS Users Workshop was held virtually from 27-29 July 2020. For the meeting agenda and links to presentations, please visit the workshop web site.

March 11, 2020 : The first official release of a UFS application, the UFS Medium Range Weather Application v1.0, is now available. For details, please visit the UFS community web site or the official NOAA press release.

2) Introduction

The Unified Forecast System (UFS) is a community-based, coupled, comprehensive Earth modeling system. The UFS numerical applications span local to global domains and predictive time scales from sub-hourly analyses to seasonal predictions. It is designed to support the Weather Enterprise and to be the source system for NOAA's operational numerical weather prediction applications.

NOAA is the agency tasked with providing the official weather and climate forecasts and warnings in the United States. First and foremost, the UFS provides a framework to engage the extensive research enterprise in the US. It creates an environment to more efficiently and effectively translate research advances into operational outcomes. The UFS also enables NOAA to simplify its production suite of forecasting models from a great many independent systems, each of which has to be improved and maintained, to a single seamless system.

The UFS community includes researchers, developers and users from NOAA, educational institutions, federal agencies, and the private sector. The UFS supports research and development in the community and accelerates the transition of research successes to operations.

UFS applications share numerical forecast system elements, including Earth-system model components (e.g. atmosphere, ocean, sea ice, land, chemistry, etc.), observation processing, pre-processing, data assimilation, forward forecasting, ensemble and probabilistic processing, and post-processing. The applications share infrastructure such as model coupling tools and workflow software.

Comprehensive and updated news on the Unified Forecast System can be found on the UFS community web page.

3) UFS at the NWS

The NWS Research to Operations (R2O) initiative's five year plan is to upgrade the current operational Global Forecast System (GFS) to run as a unified, fully coupled Next Generation Global Prediction System (NGGPS) within NEMS (NOAA Environmental Modeling System) infrastructure. Using advanced high performance computing architectures, the system will incorporate the most recent advances in weather prediction modeling from NOAA and the research community.

  • Implement a weather-scale, fully-coupled NWP System

  • Extend forecast skill beyond 8 to 10 days

  • Improve hurricane track and intensity forecast

  • Extend weather forecasting to 30 days

  • Implement the unified next generation model in regional applications (Rapidly Refreshed Convective-Allowing Ensemble Forecast system, Regional Nested Hurricane Forecast System)

  • For further details see the Applications Plan on the UFS community web site.

4) UFS at NCEP : Global Modeling Systems

In 2017 the Finite Volume Cubed Sphere (FV3) dynamical core, developed at NOAA’s Geophysical Fluid Dynamics Laboratory, was selected for the new NGGPS/UFS atmospheric model for both global and regional scales. At NCEP, the FV3 dynamical core implementation includes incorporating FV3 into NEMS, and developing advanced physics and data assimilation techniques to match or exceed the skill of operational Global Forecast System (GFS), and to transition NCEP's mesoscale modeling suite to use FV3. In addition, NOAA/NWS is working with federal partners, universities, and the community to create a fully accessible FV3-based community model, see the UFS Community page and the UFS Weather Model page on GitHub.


The first implementation of the UFS Atmospheric model in NCEP occurred on June 12th 2019 with the implementation of GFS Version 15. The major component of this implementation was to replace the global spectral model in the GFS with the FV3 dynamical core. The operational FV3GFS runs the same physics as the previous GFS, except that the Zhao-Carr microphysics was replaced with the more advanced GFDL microphysics scheme.


More details on the implementation of the GFS V15 with the FV3 dynamic core can be found in the NWS Service Change Notice, on EMC's FV3GFS page on the NWS Vlab site. Comprehensive information on the official evaluation of GFS v15 is available at the EMC Model Evaluation Group’s web site.


On 23 September 2020, the global UFS application at NCEP was implemented in the Global Ensemble Forecast System (GEFS v12). The components of this upgrade include:


  • Use of the FV3 global model (same version as GFS v15) as the atmospheric component of GEFS
  • Increase in horizontal resolution to ~25 km
  • Forecast length increased from 10 to 16 days
  • Increased from 21 to 31 members
  • Coupling the GEFS atmospheric component to the NCEP Global Wave model
  • Run a 32nd member to 5 days (GEFS-Aero) for aerosol prediction, inline aerosol representation based on GOCART (GSD-Chem).

This implementation is the first global-scale coupled system at NCEP, and will replace the existing standalone Global Wave Ensemble and the NEMS GFS Aerosol Component (NGAC). More details can be found at the EMC Model Evaluation Group’s GEFS v12 web site, the EMC GEFS web page, and the EMC GEFS-Aerosol web page.


On March 22, 2021, GFS version 16 was implemented in NCEP Operations. With this upgrade, NCEP is merging the operational global deterministic WAVEWATCH III wave model Multi_1 into the GFS system. An updated version of the WAVEWATCH III model has been coupled to the GFS using a one-way coupling scheme in which the atmospheric model provides forcing to the wave model using the NOAA Environmental Modeling System (NEMS). Additional information can be found on the EMC Model Evaluation Group’s GFS v16 website, which includes numerous links to presentations showing details on GFS v16 model/assimilation changes and performance evaluations.


5) UFS at NCEP : Advancement toward a Convection-Allowing Ensemble System

As part of NCEP’s commitment to move all atmospheric prediction components in the NCEP Production Suite (NPS) to use the UFS weather model, EMC has created the capability to run the FV3 model in a limited area configuration (*Black et al.,2021). Preliminary tests comparing 3 km forecasts nested within a global simulation with a limited area 3 km FV3 dynamic core over the CONUS have shown that the limited area FV3 produced statistically indistinguishable forecasts out to 60-h, was twice a fast, and used 50-75% fewer computational resources than the version nested within a global model.


The initial implementation of the limited area FV3 in the NPS was made on May 11, 2021 in the High-Resolution Forecast System/HiResW, with the HiResW-NMMB member of HREF replaced by a limited area FV3 member. This is a step towards the eventual implementation of the Rapid Refresh Forecast System (RRFS), a convection-allowing ensemble system having the following projected configuration:


  • Based on the limited area FV3 dynamic core
  • Rapidly updated and convection-allowing (~3 km grid-spacing)
  • Ensemble-based data assimilation
  • Ensemble forecast
  • 18 h forecast every hour
  • 36-60 h forecast every 6 hours

The RRFS is intended to facilitate the replacement of current long-standing regional systems in the NPS: NAM/NAM nests, RAP/HRRR, and HiResW/HREF in the 2023 timeframe.


*Black, T. L., J. A. Abeles, B. T. Blake, D. Jovic, E. Rogers, X. Zhang, E. A. Aligo, L. C. Dawson, Y. Lin, E. Strobach, P. C. Shafran, and J. R. Carley, 2021: A Limited Area Modeling Capability for the Finite-Volume Cubed-Sphere (FV3) Dynamical Core and Comparison with a Global Two-Way Nest. Journal of Advances in Modeling Earth Systems, 13(6), https://doi.org/10.1029/2021MS002483