Accurate weather forecasts are one of the most important functions the federal government provides to Americans. During the recent partial lapse in appropriations, the National Weather Service (NWS) has continued to perform this critical function with no degradation in forecast skill or model performance.
Excepted NWS employees are working tirelessly on mission-essential functions to protect life and property, and all of the resources needed to support the operational models and services continue to be available.
The NWS, which is the operational forecasting division of the National Oceanic and Atmospheric Administration, provides products and services to protect lives and property. The flagship weather model, known as the Global Forecast System (GFS), is the key driver of these products and services.
The ability to predict the future state of the atmosphere weeks in advance, through a set of mathematical equations that describe chaotic fluid motion, is one of the greatest achievements in modern-day science. In order to predict what the weather will be in the weeks ahead, tens of millions of atmospheric and marine observations are collected daily from around the planet and satellites in space.
Determining the current state of the atmosphere is a very complex process requiring massive supercomputers to run model code. The goal is to find a single right answer out of an infinite number of incorrect possibilities. This is done four times a day by NWS. While this is truly a monumental achievement, there is a vast amount of research yet to be done to improve the accuracy of weather forecasting.
A phenomenon in the GFS, known as forecast skill “dropout,” has recently been cited as evidence that the current partial lapse in appropriations is causing the NWS forecasts to become worse. These dropouts are a known self-correcting problem that occur once or twice a month and result in a 10-20 percent decrease in accuracy of the 5-to-10 day forecast. The model typically takes a day or two to return to its normal level of accuracy, as was the case with the dropout that occurred on Dec. 21.
Model accuracy ebbs and flows as a function of complex weather patterns. The decrease in accuracy around Dec. 25 was neither a dropout nor unexpected, and a similar trend was seen in the well-regarded European model. The fact that the accuracy was above average during the 10-day span prior to this shift gave the appearance of decreased performance.
Contrary to statements seen in the press, NWS employees do not just go in and “fix” model code every time there is a dropout. The production code is locked down, and upgrades are performed on a systematic basis. Proper evaluation of forecast model skill requires a very methodical approach, and conclusive results are obtained by monitoring statistics over months to years, not daily or even weekly fluctuations.
The Department of Commerce, working in a bipartisan fashion with Congress, has made improving the GFS accuracy one of its highest priorities. A significant amount of funding, made available in the 2018 hurricane disaster supplemental appropriations, was directed to improving data assimilation and mitigating dropouts.
Additionally, a tremendous amount of effort has gone into the development of the next-generation global forecasting system, the Finite Volume Cubed-Sphere (FV3), which will be the most significant upgrade to the dynamic core of the GFS since 1980. Development work on implementing this upgrade will continue following the end of the partial lapse in funding.
On Jan. 7, President Trump signed into law the National Integrated Drought Information System Reauthorization Act. This bipartisan legislation reauthorizes key sections of the Weather Research and Forecasting Innovation Act of 2017. Additionally, it establishes the Earth Prediction Innovation Center, which will serve as the virtual hub for development of a community FV3-GFS.
This effort will leverage recent advancements in cloud-based high-performance computing, and partnerships with industry and academia, to enhance NWS prediction capabilities.
I would like to express my deepest appreciation to all of the NWS employees who have been working tirelessly. It is an honor to help lead an organization of individuals with such dedication to the mission of protecting life and property.
Dr. Neil Jacobs is deputy administrator with NOAA.