Accumulation periods of 3-h and 24-h were evaluated out to 84-h for model output initialized at 00 UTC daily between 18 December 2008 15 December 2009. For the 12-km NAM, QPF output was interpolated to both a 15-km and 60-km verification domain, while the half-degree GFS QPF output was interpolated to the 60-km domain only. The National Centers for Environmental Prediction (NCEP) Stage II precipitation analyses for the 3-h accumulation and the NCEP/Climate Prediction Center (CPC) precipitation analyses for the 24-h accumulations were also interpolated to the same 15- and 60-km verification domains, and then compared to the forecasts.
Objective model verification statistics were generated using version 3.0 of the Model Evaluation Tools (MET) software package, which offers a wide variety of state-of-the-art verification methods. For this test, grid-to-grid comparisons were performed. The traditional metrics computed included frequency bias and Equitable Threat Score (ETS), while the advanced techniques included an object-based verification approach - Method for Object-based Diagnostic Evaluation (MODE) - and a neighborhood method - Fraction Skill Score (FSS).
Supplementary URL: http://verif.rap.ucar.edu/eval/gfs_nam_pcp/