Numerical Validation of a Coupled Probabilistic Rip Current Model and Nearshore Wave Prediction System for South Florida

A probabilistic rip current model (Dusek et al. 2014) coupled with the Nearshore Wave Prediction System (NWPS; Van der Westhuysen et al. 2014) has been expanded and tested across the South Florida region. The rip current model is a statistical model configured to predict the likelihood of hazardous rip currents. The model was created by relating lifeguard observations of rip current intensity to wave and water level measurements. Initial results throughout the 2014 winter season, based on photographic and visual rip current observations for the North Miami Beach area, demonstrate significant improvement in predicting rip current occurrence compared to the index-based system presently used at the National Weather Service (NWS) office in Miami. The coupled system was configured on a high resolution (30m) nested NWPS grid that outputs the necessary input variables for the rip current model along a 5m bathymetry contour including: total significant wave height, mean wave direction, and water level (ESTOFS; relative to MSL). An additional 72-hour post wave event parameter is included to account for surf zone bathymetry favorable for rip currents following wave events. This paper presents a description of the system design and purpose, along with the results of an extended validation period through the 2014 summer season utilizing observations from a recently deployed nearshore wave buoy and daily photographic and visual observations of the surf zone. References:

Dusek, G., A.J. Van der Westhuysen, A. Gibbs, D. King, S.Kennedy, R. Padilla, H. Seim, D. Elder, 2014: Coupling a Rip Current forecast model to the Nearshore Wave Prediction System. Proc. 94th AMS Annual Meeting, Atlanta, GA.

Van der Westhuysen, A. J., A. A. Taylor, R. Padilla-Hernandez, A. Gibbs, P. Santos, D. Gaer, H. D Cobb, J. R. Lewitsky, and J. Rhome, 2014: Enhancements to the Nearshore Wave Prediction System to provide coastal and overland hurricane wave guidance. Proc. 94th AMS Annual Meeting, Atlanta, GA.