Upgrade of Tropical Cyclone Surface Wind Field Model

Abstract : The U.S. Army Corps of Engineers (CE) tropical cyclone surface wind field model has been a very useful tool in ocean response modeling for more than a decade. Recently, its limitations were assessed in light of present knowledge and technology. Model limitations were identified and evaluated in terms of their perceived importance to ocean response modeling and the level of effort required to develop improved solutions. The limitations are summarized in this report. Two aspects of the CE model were targeted for improvement. This report describes the improvements developed for the upgraded model. First, the model was upgraded to include more computationally intensive options which give improved resolution and areal coverage. Up to seven nested grids are now available, compared to only five nests in the standard model. In a typical application, this upgrade can be used to achieve 2-km resolution around the eye (as compared to 5-km resolution often used in the standard model) and an expanded total coverage area. The second upgrade allows a more general specification of the axisymmetric pressure profile. This upgrade can be used to create wind fields with maxima at two different radii or with a broad maximum extending over a range of radii. It also provides more flexibility in fitting the shape of single peaked wind profiles. The upgraded model is demonstrated with historical hurricanes. The five-nest and seven-nest models are applied to Hurricane Camille. The fully upgraded model, with seven nests and general pressure specification, is applied to Hurricane Gilbert. This hurricane was chosen because it is well-documented by Black and Willoughby (1992) and it evolved into some nontraditional storm structures. The upgraded model was more effective than the standard CE model in simulating the storm.