An operational storm surge numerical forecasting system for the Yangtze River Estuary (YRE-SURGE): model development and validation

Most subtropical and extratropical coasts are vulnerable to tropical cyclones (TCs) and extratropical cyclones (ETCs), yet an integrated forecasting system capable of predicting both types of storm surges remains lacking. To address this gap, we developed an operational storm surge numerical forecast system for a typical subtropical estuary, i.e. the Yangtze River Estuary (YRE), which can offer surge predictions for both TCs and ETCs, and named YRE-SURGE. This system employs a two-domain nested FVCOM model as its core module, with meteorological forcing provided by a three-domain two-way nested WRF mode. When a TC approaches the YRE, a parametric TC model is integrated into the atmospheric force input to enhance the accuracy of wind predictions within the storm’s inner core. Validation results against observations in recent years yielded root-mean-square errors of 2.13 m s−1 for wind speed, 0.23 m for tidal level, and 0.18 and 0.22 m for storm surges under twelve ETC and three TC events, respectively, demonstrating the system’s reliability in simulating tides and surges in the YRE. The results also underscore the importance of accounting for remote surge influence when modelling surges in this region, particularly for negative surges induced by ETCs. A similar framework can be established for other subtropical or extratropical coasts affected by both ETCs and TCs.