A new approach to represent model uncertainty in the forecasting of tropical cyclones: The orthogonal nonlinear forcing singular vectors

Abstract

AbstractTropical cyclone (TC) track forecasting has been considerably improved in recent decades, while TC intensity forecasting remain challenging. In this study, orthogonal nonlinear forcing singular vectors (O‐NFSVs) for emulating the impact of model uncertainties are used to conduct TC ensemble forecasting experiments with the Weather Research and Forecasting (WRF) model, with a focus on improving TC intensity forecasting skill. The O‐NFSVs approach is compared with the traditional stochastic kinetic‐energy backscatter (SKEB) and stochastically perturbed parametrization tendency (SPPT) schemes. The results demonstrate that the O‐NFSVs ensembles generally provide a better representation of the model uncertainties affecting TC intensification, with much better deterministic and probabilistic skills. These results also extend to the ability to forecast TC track, although the perturbations have not been optimized for that specific purpose. The O‐NFSVs are therefore appropriate perturbation structures for describing the uncertainties of the TC intensity and track forecasting and are also favourable for recognizing the rapid intensification process.