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Morehead City, NC, United States

Suh S.W.,Kunsan National University | Lee H.Y.,Kunsan National University | Kim H.J.,Kunsan National University | Fleming J.G.,Seahorse Coastal Consulting
Ocean Dynamics | Year: 2015

In order to mitigate storm surge impacts, precise surge guidance computations for forecasters must be finished within a short period of time to allow them to provide early warning to the public. For this purpose, a coupled ADCIRC and SWAN model was applied based on multiple scenario-based, deterministic model runs for each time-varying meteorological forecast advisory on a relatively lightweight mesh with 57 k nodes covering the North Western Pacific (NWP) ocean. The mesh was designed to achieve an optimal combination of speed and accuracy on a cost-effective parallel computer with 64 cores. These models were applied for two events in 2012: typhoon Bolaven (on the west coast of Korea) and typhoon Sanba (on the south coast of Korea). The surge results for a 72-h forecast yielded relative surge height error of 34.1 to 46.4 % in ADCIRC + SWAN. The surge results from a meteorological forecast 24 h from landfall improved to 21.7 to 26.8 %. Furthermore, surge elevation results progressively approached measured values (i.e., improved) with each successive typhoon advisory owing to diminishing uncertainties in the meteorological input. In conclusion, this new efficient early warning forecast guidance workflow successfully achieved its goals of real-time storm surge simulations for forecasters, early warning, and understanding of ocean dynamics. © 2015, Springer-Verlag Berlin Heidelberg.

Reynolds-Fleming J.V.,Seahorse Coastal Consulting | Luettich R.A.,UNC Chapel Hill Institute of Marine science | Fleming J.G.,Seahorse Coastal Consulting
Estuaries and Coasts | Year: 2013

A fairly undeveloped barrier island along the mid-Atlantic coast, Onslow Beach, was exposed to two differing, yet sequential meteorological events in the fall of 2008. The response of the barrier island differed significantly enough to warrant investigation into the causes of aberrant overwash locations. Tropical Storm Hanna generated high significant wave heights for a short period of time and caused overwash events along the southern portion of Onslow Beach. The Nor'easter and subsequent wind shift after TS Hanna generated significant wave heights that were lower than during TS Hanna, yet more locations of overwash were recorded along the beach. Data from NOAA wave buoys and a nearshore deployed AWAC were analyzed to understand the underlying physics behind the recorded differences in barrier island response. These data were also used to validate a coupled hydrodynamic (ADCIRC) and waves (SWAN) model to investigate the alongshore variability. Low frequency variability, on the order of days, and tidal timing of shoreward high significant wave heights contributed to the recorded variability. © 2012 Coastal and Estuarine Research Federation.

Dresback K.M.,University of Oklahoma | Fleming J.G.,Seahorse Coastal Consulting | Blanton B.O.,RENCI Renaissance Computing Institute | Kaiser C.,Louisiana State University | And 12 more authors.
Continental Shelf Research | Year: 2013

Due to the devastating effects of recent hurricanes in the Gulf of Mexico (e.g., Katrina, Rita, Ike and Gustav), the development of a high-resolution, real-time, total water level prototype system has been accelerated. The fully coupled model system that includes hydrology is an extension of the ADCIRC Surge Guidance System (ASGS), and will henceforth be referred to as ASGS-STORM (Scalable, Terrestrial, Ocean, River, Meteorological) to emphasize the major processes that are represented by the system.The ASGS-STORM system incorporates tides, waves, winds, rivers and surge to produce a total water level, which provides a holistic representation of coastal flooding. ASGS-STORM was rigorously tested during Hurricane Irene, which made landfall in late August 2011 in North Carolina. All results from ASGS-STORM for the advisories were produced in real-time, forced by forecast wind and pressure fields computed using a parametric tropical cyclone model, and made available via the web. Herein, a skill assessment, analyzing wind speed and direction, significant wave heights, and total water levels, is used to evaluate ASGS-STORM's performance during Irene for three advisories and the best track from the National Hurricane Center (NHC). ASGS-STORM showed slight over-prediction for two advisories (Advisory 23 and 25) due to the over-estimation of the storm intensity. However, ASGS-STORM shows notable skill in capturing total water levels, wind speed and direction, and significant wave heights in North Carolina when utilizing Advisory 28, which had a slight shift in the track but provided a more accurate estimation of the storm intensity, along with the best track from the NHC. Results from ASGS-STORM have shown that as the forecast of the advisories improves, so does the accuracy of the models used in the study; therefore, accurate input from the weather forecast is a necessary, but not sufficient, condition to ensure the accuracy of the guidance provided by the system. While Irene provided a real-time test of the viability of a total water level system, the relatively insignificant freshwater discharges precludes definitive conclusions about the role of freshwater discharges on total water levels in estuarine zones. Now that the system has been developed, on-going work will examine storms (e.g., Floyd) for which the freshwater discharge played a more meaningful role. © 2013 Elsevier Ltd.

Dietrich J.C.,University of Texas at Austin | Trahan C.J.,University of Texas at Austin | Trahan C.J.,High Performance Technologies Inc. | Howard M.T.,University of Texas at Austin | And 17 more authors.
Continental Shelf Research | Year: 2012

After the destruction of the Deepwater Horizon drilling platform during the spring of 2010, the northern Gulf of Mexico was threatened by an oil spill from the Macondo well. Emergency responders were concerned about oil transport in the nearshore, where it threatened immediately the fishing waters and coastline from Louisiana to Florida. In this region, oil movement was influenced by a continental shelf with varying width, the protruding Mississippi River delta, the marshes and bayou of southern Louisiana, and the shallow sounds and barrier islands that protect the coastline. Transport forecasts require physics-based computational models and high-resolution meshes that represent the circulation in deep water, on the continental shelf, and within the complex nearshore environment.This work applies the coupled SWAN+ADCIRC model on a high-resolution computational mesh to simulate the current velocity field on the continental shelf, nearshore and marsh areas during the time that oil was visible on the surface of the Gulf. The SWAN+ADCIRC simulations account for the influence of tides, riverine discharge, winds and wind-driven waves. A highly efficient Lagrangian particle transport model is employed to simulate the surface trajectories of the oil. The transport model accounts for dispersion and advection by wind and currents. Transport is evaluated using 2-week long sequences of satellite images. During both periods, the SWAN+ADCIRC current fields alone appeared to be more successful moving the oil than when direct wind forcing was included. In addition, hypothetical oil transport is considered during two hurricane scenarios. Had a hurricane significantly impacted the northern Gulf while the spill was active, depending on the track of the storm relative to the spill location, oil would have moved farther into the marshes of southern Louisiana or farther along the shelf toward Texas than actually occurred during the spill. © 2012.

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