Procedures for Implementing Operational Nowcast/Forecast Systems

NOS has established a set of procedures for assessing the skill of its oceanographic nowcast and forecast systems developed as part of its Physical Oceanographic Real-Time Systems (PORTS). Skill assessment is critical in helping NOS ensure that these models are developed so that they are consistent with user needs, they are implemented in a scientifically sound and operationally robust way, their shortcomings are well understood, and that all products and procedures are authoritative in the face of potential legal challenges.

The components of skill assessment include the identification of the variables relevant to the intended application, model run scenarios, the comparison statistics or quantities, and the acceptance criteria. User-based skill assessment assumes that a forecast will be most useful when it includes variables specifically needed by the user, and when accuracy is high enough that specific management or operational decisions can be reliably made. The primary user for NOS's nowcasts and forecasts is the maritime navigational community. The primary forecast variables, in terms of importance to the user, are: the magnitude of the water level at all times, the times and heights of high and low water, the speed and direction of the currents at all times, and the times of slack water before flood and ebb. The scenarios describe the type of forcing and the sources of forcing data of forecasts. The statistics are a small set of quantities that are easy to define, compute, and explain and that cover global accuracy and extreme cases. Acceptance criteria include numerical values for the statistics.

The procedures are explained in detail in the pdf document NOS Technical Report NOS Procedures for Implementing Operational Nowcast and Forecast Systems for PORTS(.pdf).