What Is the Ultimate Limit of Weather Predictability?

Through high-resolution deterministic and ensemble sensitivity experiments with both regional and global models, and with both realsitically large and minute idealized initial perturbation uncertainties, this talk seeks to answer what is the ultimate predictability limit of multi-scale weather. Highlights will be given to severe weather events such as midlatitude winter storms, tropical cyclones and tornadic thunderstorms.  These experiments suggests such a limit may exist both in terms of overall global error energy at different wavelengths and in terms of feature-based verifications of individual events. Such a limit is intrnisic to the underlying dynamic system and instabilities even if the forecast model and the initial conditions are nearly perfect. Minute uncontrollable initial conditions originated from small-scale instabilities can grow upscale that will eventually limit the predictability of various weather at increasingly larger scales.