Random error growth in NMC's global forecasts

Abstract

In the tropics, large external error growth at the 200-mb level is closely associated with deep convection. The spatial structure of the external error growth in the midlatitudes suggests that the representation of orography in the model, especially over Antarctica and the Rockies, is a significant source of errors. Internal error growth in the midlatitudes is greater over the Atlantic and European regions than over the Pacific region and appears to be associated with blocking phenomena, especially over the North Atlantic and Europe. The North Hemisphere exhibits a seasonal cycle in the magnitude of error growth, but the Southern Hemipshere does not. The results suggest that, in the tropics, significant increases in forecast skill may be obtainable through both model and analysis improvement. In the midlatitudes, however, there is less potential for increases in forecast skill through model improvement, and decreasing the analysis error becomes more important. -from Authors