An Evaluation of the Weather Prediction Center’s Quantitative Precipitation Forecasts for Extreme Precipitation Events between 2012-2023

When extreme hydrometeorological events threaten the United States, quantitative precipitation forecasts (QPF) issued by the National Centers for Environmental Prediction’s (NCEP) Weather Prediction Center (WPC) play a crucial role in providing decision support to mitigate losses to life and property. Given the critical importance of accurate QPFs, this study benchmarks the skill of WPC’s QPF for extreme precipitation events. The WPC QPF, available in 6- and 24-hour accumulations for days 1-3, is evaluated for the period between 2012 and 2023.

Extreme precipitation is defined using two metrics: the 99th and 99.9th percentile precipitation values of all wet-site days from 2012 to 2023 for each River Forecast Center (RFC) region, and the 2-year average recurrence interval from the NOAA Atlas-14. Stage IV quantitative precipitation estimates are used both to evaluate WPC’s QPF and to calculate the 99th and 99.9th percentile precipitation thresholds. Evaluation metrics for this study include the critical success index (CSI), false alarm rate (FAR), and probability of detection (POD). The QPF is assessed for seasonal, temporal, and regional skill for the 00Z and 12Z forecast issuances.

Preliminary results indicate that forecast skill is highest in RFCs along the eastern and western coasts of the United States where the precipitation climatology is generally dominated by atmospheric rivers and tropical cyclones. This presentation will highlight the seasonal characteristics of these regions, providing deeper insight into the findings.