These renderings are far from perfect, and it's difficult to know whether a model's growing unreliability as it runs is due to its mismatch with reality or atmospheric chaos. Typically, weather models are fed observations from satellites, balloons, and other outposts, generating what are known as initial conditions. Along with colleagues, he convinced the weather agencies to let them chew up expensive computing cycles running identical versions of several real-life weather events. National Weather Service (NWS), would provide a credible test. Zhang hoped that the next generation of supercomputer-powered weather models, including those run by the European Centre for Medium-Range Weather Forecasts and the U.S. But until recently, global weather prediction models lacked the high resolution needed to test it by recreating the storm-forming processes driving the atmosphere's chaos. Lorenz's idea has been validated in theory. If real, this 2-week descent into chaos would set a fundamental limit to the atmosphere's predictability. "That was a revolutionary insight," says Richard Rotunno, a meteorologist at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, who was not involved in the new study. A 1969 paper by Massachusetts Institute of Technology mathematician and meteorologist Edward Lorenz introduced this dynamic, later dubbed the "butterfly effect." His research showed that two nearly identical atmospheric models can diverge widely after 2 weeks because of an initial disturbance as minute as a butterfly flapping its wings. A tiny disruption in one layer of turbulence can quickly snowball, infecting the next with its error. It's as close to be the ultimate limit as we can demonstrate," says Fuqing Zhang, a meteorologist at Pennsylvania State University in State College who led the work, accepted for publication in the Journal of the Atmospheric Sciences.įorecasters must contend with the atmosphere's turbulent flows, which nest and build on each other as they create clouds, power storms, and push forward cold fronts. In the regions of the world where most people live, the midlatitudes, "2 weeks is about right. Today, the best forecasts run out to 10 days with real skill, leading meteorologists to wonder just how much further they can push useful forecasts.Ī new study suggests a humbling answer: another 4 or 5 days. Since the 1980s, they've added a new day of predictive power with each new decade. A week later, that unlikely forecast came true-testimony to the remarkable march of such models. A few showers will linger Sunday night and into Monday, mainly early.Last month, as much of the United States shivered in Arctic cold, weather models predicted a seemingly implausible surge of balmy, springlike warmth. Highs Sunday are cooler in the mid 60s with mainly cloudy skies. Scattered showers are expected Sunday as a low pressure system approaches. A stray shower may be around late during the Vols game, but most locations should stay mainly dry.Ĭlouds will be abundant during the game though with temperatures in the mid 60s at kickoff. There is no rain chance during the daytime hours Saturday with a 30% chance for some spotty showers Saturday night. Looking ahead to this weekend, Saturday will be our drier day. It stays dry Friday night with temperatures cooling down into the low 50s once most games wrap up. If you are headed to a Friday night football game, there are no weather concerns. Highs Friday will be a touch warmer in the low 70s. The dry weather continues into Friday with a mix of sun and clouds. Tonight some clouds will build in keeping overnight lows in the mid 40s for most. Mostly sunny skies continue this afternoon with seasonable highs in the mid to upper 60s.
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