An Evaluation of Short-Term MOS and Short-Term Ensemble MOS Temperature Forecasts

A Model Output Statistics (MOS) database was produced using MySQL and the java programming language. This database allows easy access to the MOS data for verification, product output, and the generation of ensemble MOS products. The current forecast portion of the database contains the Global Forecast System (GFS) MOS, the Eta MOS, and the older Nested Grid Model (NGM) MOS. Recently, the GFS-based cooperative (COOP) MOS has been added to the database along with the Medium-Range ensemble MOS output of the 0000 UTC medium-range ensemble forecast system (MREF).

This paper will focus on the products produced from the database including graphical displays of COOP MOS, and the production of short-term ensemble (STE) MOS and verifications of these products. The current STE-MOS is produced using weights from the three short-term MOS products including the GFE-MOS, NGM-MOS and the Eta-MOS. The NGM-MOS product, though not as skillful, is used in the generation of the ensemble product, but is given a lesser weight based on its lower skill. The general weighting is based on verification and varies by season. Through most of the year the GFE-MOS weight is 3, the ETA-MOS weight is 2 and the NGM-MOS weight is 1. Thus the GFE-MOS is weighted 3 to 1 over the NGM-MOS. Due to improved verification scores, during the winter, the ETA-MOS weights are increased to 3.

The STE-MOS product demonstrates the utility of relational databases in the production and verification of ensemble MOS products. Verification of the ensemble MOS product relative to the individual GFE-MOS, NGM-MOS, and ETA-MOS will be presented. The preliminary results, based on the verification of MOS sites in Pennsylvania, suggest the ensemble (STE-MOS) product is slightly more accurate than the GFE- and ETA- based MOS products.

The database application also facilitates the storing and verification of the COOP MOS. The COOP MOS is then made available on a grid for display purposes. Comparisons of gridded STE-MOS to COOP-MOS will be presented