In early May, NWS announced it was planning to release the latest version of its signature forecasting model, the FV3-based Global Forecast System(GFS), Version 15.1. Once the NWS National Centers for Environmental Prediction (NCEP) completes a 30-day technical test successfully, this version will be the new operational model. The targeted release date is on or about Wednesday, June 12, 2019.
In February, NWS paused its implementation timeline to review user concerns about the excessive snow and a cold bias in the model and to explore other potential improvements. In the following months, NWS modified the model to alleviate excessive snow and cold bias in the model and made three key updates:
-Changed the way snow amounts were calculated and communicated to the land surface model, basing it on the fraction of frozen precipitation falling on the ground rather than on the total precipitation in cold conditions
-Refined the interaction of radiation with cloud particles, allowing for each type of hydrometeor (convective rain, stratiform rain, snow, graupel, and ice) to assume its own physical characteristics as calculated by the Geophysical Fluid Dynamics Laboratory microphysics scheme (like particle radius) and interact accordingly with the radiation scheme
-Updated the supersaturation parameter over ice in the data assimilation system.
The results show an improvement over biases previously found in the model.
Additionally major changes include:
-Updating data assimilation to take in NPOESS Preparatory Project Ozone Mapping Profiler Suite ozone
-Placing NOAA-19 Solar Back-scatter Ultraviolet Instrument/2 ozone in monitor
-Assimilating Meteosat-11 Spinning Enhanced Visible and InfraRed Imager Channels 5 and 6
-Updating quality control for GOES Satellite AMVs in preparation for GOES-17.
If GFSv15.1 is implemented in June, GFSv14 model output will remain available through September 30, 2019, on the NCEP Model Analyses and Guidance (MAG) Evaluation website and NOAA National Operational Model Archive and Distribution System (NOMADS) Para-NOMADS Website.