The Performance of MOS in the Digital Age

Abstract

Model output statistics (MOS) guidance forecasts have been produced for over three decades. Until recently, MOS guidance was prepared for observing stations and formatted in text bulletins while official National Weather Service (NWS) forecasts for stations and zones were prepared by forecasters typing text. The flagship product of today?s NWS is the National Digital Forecast Database (NDFD). In support of NDFD, MOS is now also produced on grids. This paper compares MOS and gridded MOS (GMOS) to the forecaster-produced NDFD at approximately 1200 station locations in the conterminous United States. Results indicate that GMOS should provide good guidance for preparing the NDFD. In those areas of the country where station observations well represent the grid, GMOS features accuracy comparable to that of NDFD. In areas of complex terrain not well represented by station observations, GMOS appears similar to NDFD in its depiction. A new score is introduced to measure convergence from a long-range forecast to the final short-range forecast. This shows good GMOS forecast continuity when compared to station MOS and NDFD.