Handout (275.0 kB)
MODE precipitation verification was applied to two versions of the NCEP global numerical weather prediction model the GFS (T574, 27km resolution) model and the GFSX (T1534, 13km resolution) model to the 2014 seasons. The T1534 GFSX was implemented for operation on January 14, 2015 and replaced the previous operational T574 GFS. Multiple thresholds combined with a fixed smoothing radius were used for the MODE identification of objects. The 00Z forecasted 24-hour precipitation accumulations ending on the 36, 60, 84, 108, 132, 156, and 180 forecast lead times from the models were compared to Climatologically Calibrated Precipitation Analysis (CCPA) observations. The Median of the Maximum Interest with respect to observation objects (MMIO) is an output summary statistic generated for each MODE run, and is useful when aggregated across multiple cases to assess overall model performance. Larger values of MMIO indicate higher interest values which imply better matches across forecast and observation fields. For all four seasons in 2014, the GFSX generally has larger MMIO values than the GFS during most forecast lead times. In the summer for both model versions, the MMIO values are lowest compared to other seasons, and there seems to be a larger drop in MMIO values with forecast lead time. Both the GFS and GFSX tend to overestimate light rain and underestimate heavy rain, but the GFSX is frequently closer to observations compared to the GFS. The GFSX is also closest to observations in total object count, especially in summer where the GFS largely underestimates the number of precipitation objects. In winter and spring of 2014, the GFSX overestimates total object count.
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