An Evaluation of Sea Level Cyclone Forecasts Produced by NMC's Nested-Grid Model and Global Spectral Model

Abstract

Abstract Sea level cyclone errors are computed for the National Meteorological Center's Nested-Grid Model (NGM) and the Aviation Run of the Global Spectral Model (AVN). The study is performed for the 1987/88 and 1989/90 cool seasons. All available 24- and 48-h forecast cycles are analyzed for North America and adjacent ocean regions. Forecast errors in the central pressure, position, and 1000-500-mb thickness of the cyclone center are computed. Aggregate errors can be summarized as follows: NGM forecasts of central pressure are too low (forecast pressure lower than analyzed) by 0.72 mb at 24 h and 0.66 mb at 48 h, while AVN forecasts are too high by 2.06 mb at 24 h and 2.50 mb at 48 h. Variance statistics for the pressure error indicate that AVN forecasts possess less variability than those of the NGM. Both mean absolute displacement errors and mean vector displacement errors are smaller for the AVN. The NGM moves surface cyclones too slowly and places them too far poleward into the cold air; the AVN poss...