NOAA Upgrades Global Ensemble Forecast System

NOAA’s Global Ensemble Forecast System (GEFS) is undergoing significant upgrades to expand its capabilities and improve weather forecasting. Meteorologists at the National Weather Service use GEFS to produce medium-range weather forecasts and to issue watches and warnings during high-impact weather events, including hurricanes, blizzards, and extreme heat and cold.

GEFS now uses the Finite-Volume Cubed-Sphere (FV3) dynamical core that was similarly added to the Global Forecast System model in 2019. With today’s upgrade, the National Weather Service can deliver first-ever numerical weather predictions three and four weeks in advance, providing more lead time for decision making than ever before.

“This significant upgrade to GEFS – the first of its kind in five years – will improve probabilistic weather model guidance for public safety, quality of life and business decisions that drive U.S. economic growth,” said Neil Jacobs Ph.D., acting NOAA administrator. “These continued advancements underscore the Trump Administration’s commitment of improving our weather forecasting to protect life and property.”

With the inclusion of the FV3 dynamical core, GEFS resolution has increased from approximately 33km to 25km, and the number of individual forecasts input into the ensemble has increased from 21 to 31. These changes will allow models to run at a higher resolution of detail and provide better accuracy. Additional upgrades include extending the forecast length from 16 to 35 days, along with improvements to the physics. GEFS attempts to quantify the amount of uncertainty in a forecast by varying the known inputs to multiple forecasts, thereby generating a range of possible outcomes.

“This GEFS upgrade continues the ongoing revolution of numerical modeling that began with the introduction of ensemble modeling into operations over 25 years ago,” said Louis W. Uccellini, Ph.D., director of NOAA’s National Weather Service. “This new version will provide additional forecast skill and extended lead-times for the prediction of extreme weather and water events; and to address important forecast challenges in weeks three and four with a higher-resolution ensemble system.”

During testing the upgraded GEFS enabled improved severe weather forecasts, including hurricane track and intensity, precipitation, wave heights, and aerosol for all regions across the globe. Additionally, this GEFS enhancement will boost extended range forecasting in the 2-4 week timescale by improving the numerical guidance used for temperature and precipitation forecasts. GEFS will also improve the prediction of week-two tropical cyclone activity, which will help forecasters improve the skill of the Global Tropics Hazard Outlook.

For the first time, GEFS now couples wave and aerosol components with the atmospheric model, which allows for simplification of the operational National Centers for Environmental Prediction (NCEP) production suite. GEFS, and NOAA’s other weather forecasting systems and models, are developed by the Environmental Modeling Center (EMC) in College Park, Maryland, which is part of the National Weather Service, in collaboration with NOAA research scientists and the broader modeling community.

“If our upgrade to the Global Forecast System last year (GFS) was like upgrading the engine in a car, this upgrade to GEFS is like replacing the engines in a fleet of cars,” said Ivanka Stajner, Ph.D., acting director of NOAA’s Environmental Modeling Center. “Each car takes advantage of the power of this new engine, and with slightly different features, they represent the forecast uncertainties more accurately, aiding the forecasters and decision makers with information on a range of possibilities to be considered when issuing the forecasts.”

NOAA Oceanic and Atmospheric Research scientists originally developed the FV3 as a tool to predict long-range weather patterns at time frames ranging from multiple decades to interannual, seasonal and subseasonal. In recent years, creators of the FV3 at NOAA’s Geophysical Fluid Dynamics Laboratory collaborated with EMC scientists and expanded it to become the engine for NOAA’s next-generation operational modeling systems. The atmospheric composition model in the GEFS upgrade that integrates weather and aerosol forecasting based on the FV3 framework is the result of more than five years of model development at NOAA.

These advancements set the stage for future upgrades and are a big step towards advancing NOAA’s operational global forecast capabilities using the Unified Forecast Systemoffsite link (UFS) framework, while also fulfilling requirements of the Weather Research and Forecasting Innovation Act of 2017.

The forecasting improvements enabled by this upgrade to GEFS directly support National Weather Service objectives for improved weather forecasts and increasing the lead time for warnings of extreme events, building a more Weather-Ready Nation.

Read more at NOAA

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