Verification at NWS River Forecast Centers

Lee Cajina and Edwin Welles

National Weather Service

The National Weather Service (NWS) has started verifying river forecasts issued at River Forecast Centers (RFCs) across the country. To help the RFCs in the verification process, the Office of Hydrologic Development (OHD) developed the Interactive Verification Program (IVP), which provides tools for completing the verification process in a single environment. Along with the software, OHD provided the RFCs with some guidelines for verifying forecasts within IVP. IVP uses a mix of traditional (e.g. mean squared error, absolute error) and others not so common to NWS River Forecast verification (e.g. Probability of Detection and False Alarm Rate). Some of the more recent work has focused on adding distribution‑based statistics (Kolmogorov ‑ Smirnov test statistic and the discrimination score).

Despite this effort to provide an environment for a thorough verification analysis, few RFCs are currently using the tools developed by OHD. In addition to software constraints and a limited dataset, it is not clear which statistics are most meaningful. There is also disagreement about the validity of using the statistical results for making comparisons across regions. To help determine which statistics are most useful, OHD recently initiated a study to evaluate the statistics computed in IVP. This study should provide insight into strengths and weaknesses of each statistic and which ones are most appropriate for different criteria and across regions.

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