In May 2000, the Meteorological Development Laboratory (MDL) of the National Weather Service (NWS) implemented a completely new Model Output Statistics (MOS) guidance package. This new product was developed from output of the NWS Global Forecast System (GFS). Guidance was provided for the 0000 and 1200 UTC forecast cycles at nearly twice the number of sites available in the MOS alphanumeric package based on the Nested Grid Model (NGM). In addition, the new GFS-based MOS package contained guidance for forecast projections out to 72 hours. Subsequent enhancements to the GFS MOS product suite included guidance for other weather elements, provided guidance for the 0600 and 1800 UTC cycles of the GFS, and increased the number of sites with guidance to over 1500 locations in the contiguous United States, Alaska, Hawaii, Puerto Rico, and the Virgin Islands.

A second major implementation in early 2002 introduced MOS guidance based on the NWS Eta model for over 1200 sites in the contiguous United States. Although the initial Eta-based MOS package contained only a subset of the weather element guidance provided by the GFS MOS system, the Eta-based MOS guidance gave forecasters another tool for producing their final forecasts. In fact, preliminary verifications showed that the Eta-based MOS guidance was equal to or better than the GFS-based MOS guidance at the earlier projections out to approximately 36 hours.

In this talk, we describe the current status of the GFS- and Eta-based MOS guidance. We discuss some of the developmental details, including the definitions of the weather elements for which guidance is generated. Comparative verifications among the two new systems and the baseline NGM MOS system are shown for a number of the weather elements for approximately 300 sites in the contiguous United States. We also present a series of changes being considered to improve the MOS products.