TY - GEN
AU - Peter Janssen
AB - The ECMWF freak wave warning system is based on a random time series analysis using the envelope wave height. The key quantity of interest is the maximum envelope wave height distribution which for (weakly) nonlinear systems depends on envelope skewness and kurtosis. Expressions for skewness and kurtosis for general spectra are presented, but they are very cumbersome. Therefore, a simple parametrization of skewness and kurtosis of the bound waves and the contribution of the free waves to kurtosis is presented. These parametrisations are validated against computations using the theoretical expressions of the statistical parameters. By adjusting a few parameters in the parametrizations a good agreement with the ’exact’ computations is found. These parametrizations have been introduced in the operational version of ECMWF’s freak wave warning system.
BT - Technical Memoranda
CY - Reading
DA - 08/2025
DO - 10.21957/af89ffdc01
M1 - 930
N2 - The ECMWF freak wave warning system is based on a random time series analysis using the envelope wave height. The key quantity of interest is the maximum envelope wave height distribution which for (weakly) nonlinear systems depends on envelope skewness and kurtosis. Expressions for skewness and kurtosis for general spectra are presented, but they are very cumbersome. Therefore, a simple parametrization of skewness and kurtosis of the bound waves and the contribution of the free waves to kurtosis is presented. These parametrisations are validated against computations using the theoretical expressions of the statistical parameters. By adjusting a few parameters in the parametrizations a good agreement with the ’exact’ computations is found. These parametrizations have been introduced in the operational version of ECMWF’s freak wave warning system.
PB - ECMWF
PP - Reading
PY - 2025
T2 - Technical Memoranda
TI - Review of Freak Wave Research at ECMWF
UR -  
ER -