Hurricane storm surge simulations comparing three-dimensional with two-dimensional formulations based on an Ivan-like storm over the Tampa Bay, Florida region

We provide a dynamics-based comparison on the results from three-dimensional and two-dimensional simulations of hurricane storm surge. We begin with the question, Whatmay have occurred in the Tampa Bay, Florida vicinity had Hurricane Ivan made landfall there instead of at the border between Alabama and Florida? This question is explored using a three-dimensional, primitive equation, finite volume coastal ocean model. The results show that storm surges are potentially disastrous for the Tampa Bay area, especially for landfalls located to the north of the bay mouth. The worst case among the simulations considered is for landfall at Tarpon Springs, such that the maximum wind is positioned at the bay mouth. Along with such regional aspects of storm surge, we then consider the dynamical balances to assess the importance of using a three-dimensional model instead of the usual, vertically integrated, two-dimensional approach to hurricane storm surge simulation. With hurricane storm surge deriving from the vertically integrated pressure gradient force tending to balance the difference between the surface and bottom stresses, we show that three-dimensional structure is intrinsically important. Two-dimensional models may overestimate ( or underestimate) bottom stress, necessitating physically unrealistic parameterizations of surface stress or other techniques for model calibration. Our examination of the dynamical balances inherent to storm surges over complex coastal topography suggests that three-dimensional models are preferable over two-dimensional models for simulating storm surges.