Nearshore Wave Prediction System Model Output Statistics (NWPS MOS): Improvement of NOAA Probabilistic Rip Current Forecast Model

The National Weather Service (NWS) and the National Ocean Service (NOS) are collaboratively transitioning the NOAA probabilistic rip current forecast model into NWS operations. This model predicts the statistical likelihood of hazardous rip currents using a logistic regression technique with predictor inputs of significant wave height, mean wave direction, water level, and a bathymetry proxy. In a staged implementation along the US coasts, the model is running experimentally as a component of the National Center for Environmental Prediction (NCEP)’s Nearshore Wave Prediction System (NWPS).

The NWS Meteorological Development Laboratory (MDL) is responsible for the evaluation of the model before its national implementation. Initial evaluation results are encouraging; however, the model tends to under-forecast the occurrence of rip currents at Mission Beach, CA, Miami Beach, FL, and Salisbury Beach, MA. Since MDL has collected rip current observation reports at Mission Beach and archived NWPS model data in the San Diego area, we have developed a locally-adjusted logistic regression equation. Using MDL’s Model Output Statistics (MOS) approach, we have been able to improve upon the experimental NOAA model.

This presentation will summarize input data sources (predictand and predictors), the NOAA probabilistic rip current model, and initial verification results. We will show resulting improvements with NWPS MOS product in verification as well as discuss the interpretation with regard to strengths, weaknesses, and room for improvement. We conclude by considering future research with a focus on operational implementation.