Effects of Climate Variability and Change on Gulf of Mexico Tropical Cyclone Activity

Abstract

Abstract According to three recent assessments, hurricane activity will likely increase in the future. If true, this raises the possibility that new coastal and offshore facilities are being under-designed, and that older facilities may need hardening in order to maintain presently accepted risk levels. This study presents the latest results from ongoing research that aims to narrow the uncertainties in hurricane activity over the next 50 years using a powerful combination of the latest dynamical and statistical techniques, with particular focus on the Gulf of Mexico. The recent increase in computational capacity has enabled dynamical assessments in unprecedented detail. The benefits of enhanced model resolution are determined together with an assessment of sensitivity of tropical cyclone activity to critical details of the experimental approach. Storm frequency and storm intensity are shown to increase with increasing model resolution, yet preferred locations and timings of storm activity within the basin and across the hurricane season appear insensitive to both model resolution and details of the model setup; thereby enhancing confidence in previously published results on future increases in storm frequency and intensity. Statistical and dynamical assessments both show an increase in tropical cyclone frequency of 1 to 3 storms by the mid 21st century, further increasing the level of confidence in this prediction. These latest technologies and techniques are being developed directly into industry-relevant decision tools. One such tool, the Willis Hurricane Index, translates hurricane parameters into quantitative damage assessments and when combined with high resolution simulations can produce damage assessments over the next 50 years. Introduction Globally averaged intensity of tropical cyclones will shift towards stronger storms under predicted climate change scenarios, with intensity increases of 2-11% by 2100 according to an assessment by a World Meteorological Organization Expert Team on Climate Change Impacts on Tropical Cyclones (Knutson et al, 2010). They also state that existing modeling studies consistently predict decreases in the globally averaged frequency of tropical cyclones, by 6-34% yet substantial increases in the frequency of the most intense cyclones. The synthesis reports of IPCC (2007) and CCSP (2008) are in general agreement with these assessments. Predicted changes for individual basins; however, show large variations between different modeling studies and there is disagreement on whether numbers of storms in individual basins will increase or decrease (e.g. Knutson et al 2007, Bengtsson et al 2007).