Predictive skill of an NWP system in the southern lower stratosphere

Abstract

AbstractThe predictive skill of the Australian Bureau of Meteorology's Global Assimilation and Prediction (GASP) system in the southern lower stratosphere is examined using two different sets of diagnostics: (i) conventional verification statistics used in numerical weather‐prediction studies (namely, root‐mean‐square (RMS) error, anomaly correlation, and bias), and (ii) elliptical diagnostics of the polar vortex (defined using potential vorticity on isen‐tropic surfaces). Both sets of diagnostics indicate the same variation in predictive skill for forecasts during October 1994. The stratospheric forecasts are a large improvement over persistence even at seven days, with the performance at s..