According to this ECMWF planning document (page 14, figure 4): http://www.ecmwf.int/about/programmatic/strategy/strategy.pdf http://www.ecmwf.int/about/program

According to this ECMWF planning document (page 14, figure 4): http://www.ecmwf.int/about/programmatic/strategy/strategy.pdf http://www.ecmwf.int/about/programmatic/strategy/strategy.pd... the forecast skill for ECMWF and NOAA have been improving pretty steadily over the last 15 years. Basically, we're seeing two days farther into the future now than 20 years ago. I agree that chaotic dynamics and various noise sources limit the time horizon for weather predictions to perhaps 2 weeks.