The Asymmetry of Coastal Water Level Response to Landfalling Hurricanes Simulated by A Three-Dimensional Storm Surge Model

The asymmetry of tropical cyclone-induced maximum coastal sea level rise (positive surge) and fall (negative surge) is studied using a three-dimensional storm surge model. It is found that the negative surge induced by seaward blowing winds is more sensitive to wind speed and direction changes than the positive surge induced by onshore winds. As a result, negative surge is inherently more difficult to forecast than positive surge since there is uncertainty in hurricane wind forecasts. The asymmetry between negative and positive surge is more apparent in shallow water regions, and under stronger winds. For a tropical cyclone with a fixed central pressure, the surge asymmetry increases with decreasing storm translation speed. On the other hand, for a constant translation speed, the surge asymmetry increases as a tropical cyclone's RMW increases. Tropical cyclone's wind inflow angle can also affect surge asymmetry. A set of idealized cases as well as two historic tropical cyclone cases, Hurricanes Charley (2004) and Isabel (2003), are used to illustrate the surge asymmetry induced by landfalling hurricanes.