The dependence of short-range surface cyclone forecasts on the large- scale circulation: a preliminary assessment

Sea level cyclone errors for two contrasting planetary-scale flow regimes, a long-wave trough verses a longwave ridge over western North America, are computed for the National Meteorological Center's Nested Grid Model (NGM) and "Aviation Run' of the Global Spectral Model (AVN). The study is performed for the 1987/8 and 1989/90 cool seasons (1 December-31 March). Statistically significant differences in forecast skill are found between the two flow patterns. This finding suggests that the utility of cyclone forecasts can be improved if model performance is documented for other recurrent, persistent flow regimes. -from Authors