Search

Hurricane Michael (2018) made landfall near Mexico Beach, FL, as a Category 5 hurricane, with gauge‐measured water levels over 4 m. Wind and pressure fields were created by blending a parametric near‐field model with a gridded far‐field model. Winds and modeled water levels were well validated across Michael's large impact a‐ea. A detailed analysis of the coastal surge caused by Michael demonstrates that advection contributed significantly to Michael's highest water levels and the timing of the water level across a large portion of the Michael impact area. A momentum balance in a streamwise‐normal coordinate system demonstrates that the advection contributions due to spatial gradients in the flow are identified with streamwise convergence/expansion of the flow field (Bernoulli acceleration) and curvature in the flow field (centrifugal acceleration). These effects are created by the regional geometry and the storm's wind field and are most likely to affect back barrier water levels and along curved coastlines. These findings provide an improved understanding of the role of advection in determining storm surge and, thus, the importance of including it in storm surge models. In 2018, Hurricane Michael hit Mexico Beach, FL, as a Category 5 hurricane, with peak water levels over 4 m. Michael’s flooding was studied using computational models that simulated the storm’s water levels and currents. These models revealed the influence of the storm’s wind patterns and regional geography on water levels and their distribution across the impacted region, particularly emphasizing the flow velocity field surrounding Mexico Beach and the inlet to St. Joseph Bay. Such insights clarify the role of specific flow dynamics and highlight the importance of capturing them accurately in numerical simulations of storm‐induced water surge. Advection substantially enhanced Michael’s storm surge across a large portion of the Michael impact areaCentrifugal acceleration from flow curvature was the main advection process affecting water levels along the coast during Hurricane MichaelBernoulli acceleration plays an important role back‐barrier in water levels where flow contractions/expansions are present Advection substantially enhanced Michael’s storm surge across a large portion of the Michael impact area Centrifugal acceleration from flow curvature was the main advection process affecting water levels along the coast during Hurricane Michael Bernoulli acceleration plays an important role back‐barrier in water levels where flow contractions/expansions are present

A finite element FE model is used to study tides and hurricane storm surge in the Gulf of Mexico in the region ranging from the Mississippi Sound to the northwest coast of Florida. Issues that are emphasized include the use of large domains, the importance of a high degree of grid resolution in coastal regions of interest, the use of meshes with highly varying nodal densities to minimize the size of the discrete problem, and the use of the generalized wavecontinuity equation GWCE for FEbased solutions to the shallowwater equations. The computations presented are unprecedented in their scope, level of localized detail, and degree of gridsize variability. The GWCEbased FE model leads to very accurate and efficient flow solutions.

A Gulf of Mexico performance evaluation and comparison of coastal circulation and wave models was executed through harmonic analyses of tidal simulations, hindcasts of Hurricane Ike (2008) and Rita (2005), and a benchmarking study. Three unstructured coastal circulation models (ADCIRC, FVCOM, and SELFE) validated with similar skill on a new common Gulf scale mesh (ULLR) with identical frictional parameterization and forcing for the tidal validation and hurricane hindcasts. Coupled circulation and wave models, SWAN+ADCIRC and WWMII+SELFE, along with FVCOM loosely coupled with SWAN, also validated with similar skill. NOAA's official operational forecast storm surge model (SLOSH) was implemented on local and Gulf scale meshes with the same wind stress and pressure forcing used by the unstructured models for hindcasts of Ike and Rita. SLOSH's local meshes failed to capture regional processes such as Ike's forerunner and the results from the Gulf scale mesh further suggest shortcomings may be due to a combination of poor mesh resolution, missing internal physics such as tides and nonlinear advection, and SLOSH's internal frictional parameterization. In addition, these models were benchmarked to assess and compare execution speed and scalability for a prototypical operational simulation. It was apparent that a higher number of computational cores are needed for the unstructured models to meet similar operational implementation requirements to SLOSH, and that some of them could benefit from improved parallelization and faster execution speed. ADCIRC, FVCOM, and SELFE perform similarly for tides and storm surgeSLOSH did not simulate storm surge as accurately as unstructured modelsSLOSH is computationally less costly than the unstructured models.

The focus of this paper is a systematic determination of the relationship between grid resolution and errors associated with computations of hurricane storm surge. A grid structure is sought that provides the spatial resolution necessary to capture pertinent storm surge physics and does not overdiscretize. A set of numerical experiments simulating storm surge generation over 14 grid discretizations of idealized domains examines the influence of grid spacing, shoreline detail, coastline resolution and characteristics of the meteorological forcing on storm surge computations. Errors associated with a given grid are estimated using a Richardson‐based error estimator. Analysis of the magnitude and location of estimated errors indicates that underresolution on the continental shelf leads to significant overprediction of the primary storm surge. In deeper waters, underresolution causes smearing or damping of the inverted barometer forcing function, which in turn results in underprediction of the surge elevation. In order to maintain a specified error level throughout the duration of the storm, the highest grid resolution is required on the continental shelf and particularly in nearshore areas. The disparity of discretization requirements between deep waters and coastal regions is best met using a graded grid. Application of the graded gridding strategy to the hindcast of Hurricane Camille reinforces the necessity of using a grid that has high levels of resolution in nearshore regions and areas of complex coastal geometry. © 1998 John Wiley & Sons, Ltd.

A finite element (FE) model is used to study tides and hurricane storm surge in the Gulf of Mexico in the region ranging from the Mississippi Sound to the northwest coast of Florida. Issues that are emphasized include the use of large domains, the importance of a high degree of grid resolution in coastal regions of interest, the use of meshes with highly varying nodal densities to minimize the size of the discrete problem, and the use of the generalized wave‐continuity equation (GWCE) for FE‐based solutions to the shallow‐water equations. The computations presented are unprecedented in their scope, level of localized detail, and degree of grid‐size variability. The GWCE‐based FE model leads to very accurate and efficient flow solutions.

Abstract: PSWIMS (ProfilingShallowWaterInstrumentMountingSystem) is a relatively simple instrumentation system that has been developed to remotely collect vertical profiles of physical and chemical parameters in shallow water that is subject to significant changes in depth. The system is designed for observations that can not practically be made with moored sensors (due to the high cost of multiple sensors, the physical size of sensors, or the inability of moored instruments to accommodate changes in water depth) or with hand held sensors (due to the need for frequent observations over extended periods of time). Results are presented from two field deployments that demonstrate the utility of PSWIMS for measuring horizontal flux and for monitoring water quality parameters in shallow water.

One class of surface water models is the shallow water models obtained by depth-averaging the microscale mass and momentum balances. Application of shallow water models to large scale problems (on the order of 1000's of km) requires the use of spherical coordinates. Traditionally, balance laws in spherical coordinates are derived by simply expanding the spatial operators in the standard depth-averaged equations. However, the equations themselves are based on an assumed planar surface so that an inconsistency exists between the derivation and the interpretation. In this article, a method is presented that properly accounts for the curvature of the Earth during the depth-averaging procedure. The derivation gives rise to new terms in both the continuity and momentum balances, terms that we refer to as curvature terms. A scaling analysis evaluates the magnitude of the terms. It is shown that the curvature term in the continuity balance is insignificant when the vertical velocity is small, i.e., at least four orders of magnitude less than lateral components. Similarly, when the vertical velocity is small, the curvature term in the momentum balance that comes from the convective terms is insignificant. The second curvature term in the momentum balance is associated with the macroscopic stress tensor; it is on the same order of magnitude as other stress terms and should be retained when momentum dissipation is modeled. Finite element discretization of the resulting balance laws utilizes the generalized wave continuity equation which, because of its monotonie dispersion relation, eliminates noise in the solution without resorting to artificial damping. A cartographic mapping simplifies finite element implementation in spherical coordinates so that Cartesian master elements can be used. Finally, an application to the Western North Atlantic and Gulf of Mexico illustrates the importance of using equations in spherical coordinates for large scale applications.