On September 23, the National Weather Service (NWS) announced a significant upgrade to its operational Global Ensemble Forecast System (GEFS), the first of its kind in nearly five years and first to include atmosphere-wave-aerosols coupling. The GEFSv12 upgrade inaugurates a new era of NOAA’s global forecast capabilities, fueled by innovations introduced by the Unified Forecast System (UFS) community modeling framework. GEFSv12 sets the stage for simplifying NOAA’s operational forecast suite. Operational forecast data from GEFSv12 are now available online alongside visual forecast aids at the NCEP Model Analyses and Guidance website.
“The National Weather Service uses GEFS to produce medium-range weather forecasts and provide reliable outlooks of impending high-impact weather events, including hurricanes, blizzards, and extreme heat and cold out to 7 to 10 days in advance. With today’s upgrade, we will deliver our first ever weather predictions three to four weeks in advance,” said NWS Director Dr. Louis Uccellini during a science briefing for the media.
The GEFSv12 upgrade provides a solid foundation for improving the probability forecast guidance for weeks one and two and monthly forecasts for temperature and precipitation outlooks. Its products will become an important component in the sub-seasonal to seasonal forecasts issued by NOAA’s Climate Prediction Center (CPC). Additional advances included in GEFSv12 will provide more lead time for storm preparations than ever before. “This is a critical element that helps us build a more Weather-Ready Nation,” emphasized Dr. Uccellini.
The GEFSv12 upgrade addresses significant challenges in the extended range portion of forecasts. GEFS resolution increased from approximately 33 km to 25 km, and the number of individual forecasts — ensemble members — has been expanded from 21 to 31. In his remarks, Dr. Uccellini highlighted that “the GEFS upgrade continues the ongoing revolution of numerical modeling that began with the National Weather Service leading the world with the introduction of ensemble modeling into operations over 28 years ago”.
GEFSv12 is also making history at NOAA by becoming the first global-scale operational system with coupled components. As part of the efforts to simplify the operational weather forecasting suite, GEFSv12 became a pioneer by including the coupling of its atmospheric ensemble component (FV3) with a wave model ensemble (WAVEWATCH III) and a NEMS GFS aerosol deterministic component (NGAC). Scientists from NOAA’s Geophysical Fluid Dynamics Lab (GFDL) worked alongside NOAA Research (OAR) and NWS developers at the Environmental Modeling Center (EMC) to expand GEFS. “The GEFS upgrade is an engine for our next generation of operational modeling systems,” said Dr. Ivanka Stajner, acting Director of NOAA’s Environmental Modeling Center.
Simplifying NOAA’s model suite will be accomplished using the UFS framework to include coupled components such as ocean circulation, land, coastal systems, the cryosphere, and space weather at higher resolutions. “We expect to get even more accurate forecasts out of that, especially for the extreme events out into weeks two, three, and four, to give even more preparation time for these types of events,” remarked Dr. Uccellini. Such advances are crucial for giving the emergency management community an early start, helping to save lives and protect property.