An evaluation of sea level cyclone forecasts produced by NMC's nested-grid model and global spectral model

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 possesses a smaller, slow bias only. Both models contain a weak cold bias as judged from the 1000-500-mb thickness over the cyclone center. -from Authors