The National Weather Service has launched a powerful new weather forecasting model, just in time for the U.S. Atlantic hurricane season. But some meteorologists worry that, even after years of testing, the model is still not ready for prime time.
Over the last year, the weather service has been testing the upgraded tool, using it to do retrospective forecasts of three hurricane seasons and three seasons of winter storms. The researchers then compared those forecasts with those of the previous forecast model, known as the Global Forecast System, or GFS.
Scientists hope that the new model — called GFS-FV3, for Finite-Volume Cubed-Sphere Dynamical Core — is going to improve the accuracy of U.S. weather predictions, currently in third place behind those of two other European weather agencies (SN Online: 9/21/17). Its the first significant upgrade to the GFS in about 40 years. And so far, the tests suggest that the FV3 model has more accurate five-day forecasts, as well as better predictions of hurricane tracks and intensification.
A dynamical core is the engine of a weather model, solving equations that describe the numerous, complex physical interactions between the atmosphere and ocean, so that they can be incorporated into the model. Launched June 12, the new model produces more detailed images faster than the previous one, which means that it can incorporate more weather processes that might otherwise be missed, the weather service says. Unlike the previous GFS model, GFS-FV3 is also able to simulate vertical movements such as updrafts, a key component of severe weather, at very high resolution.
When it comes to forecasting hurricane tracks, the FV3 model showed some promise during the 2018 storm season. Its prediction of the track of Hurricane Lane, which struck Hawaii in August, had fewer errors than any other system, including the existing U.S. model as well as the top-performing tools, the United Kingdoms Met Office model and the European Centre for Medium-Range Weather Forecasts model.
But some hitches appeared in the models predictions over the last winter. One problem was that a monthlong U.S. government shutdown in December and January delayed scheduled testing of the new model at the National Oceanic and Atmospheric Administrations Environmental Modeling Center (SN Online: 1/12/19). As a result, the models launch date was pushed back from late January to March.
More worryingly, the model had an apparent “cold bias in the lower atmosphere,” as a memo from the weather service noted in February, which caused it to dramatically overpredict snow amounts along the busy northeastern corridor between Boston and Washington, D.C.
Over the winter, meteorologists who have kept an eye on the models predictions (publicly available since March 2018) worried aloud on social media sites such as Twitter that the model isnt ready to take over as the primary U.S. weather-prediction tool. “Scary that this is what we are about to go with on a permanent basis,” tweeted Doug Kammerer, chief meteorologist for NBC Washington, on February 13.
Following this criticism, the launch date was postponed for several months again. On April 4, government scientists released a new configuration of the FV3 model that they said removed the cold bias and “showed a clear improvement” in excessive snowfall predictions. But the model still predicted somewhat more snowfall than was observed in some of its test cases, such as the January Read More – Source