Abstract
Abstract. In view of the high vulnerability of the small islands of the Lesser Antilles to cyclonic hazards, realistic very fine scale numerical simulation of hurricane-induced winds is essential to prevent and manage risks. The present innovative modeling aims at combining the most realistically simulated strongest gusts driven by tornado-scale vortices within the eyewall and the most realistic complex terrain effects. The Weather Research and Forecasting (WRF) model with the nonlinear backscatter and anisotropy (NBA) large eddy simulation (LES) configuration was used to reconstruct the devastating landfall of category 5 Hurricane Irma (2017) on Saint Barthélemy and Saint Martin. The results pointed out that the 30 m scale seems necessary to simulate structures of multiple subtornadic-scale vortices leading to extreme peak gusts of 132 m s−1 over the sea. Based on the literature, such extreme gust values have already been observed and are expected for category 5 hurricanes like Irma. Risk areas associated with terrain gust speed-up factors greater than 1 have been identified for the two islands. The comparison between the simulated gusts and the remote sensing building damage highlighted the major role of structure strength linked with the socio-economic development of the territory. The present modeling method could be easily extended to other small mountainous islands to improve the understanding of observed past damage and to develop safer urban management and appropriate building standards.
Highlights
As described by Cécé et al (2016), the Lesser Antilles Arc includes small tropical islands where a total of 1.8 million people live, from Tobago (11.23◦ N, 60.67◦ W) to the Virgin Islands (18.34◦ N, 64.93◦ W)
The innovative originality of this new modeling approach aims at combining the most realistic simulated strongest gusts driven by tornado-scale vortices within the eyewall and the most realistic effects of the small mountainous island complex terrain
The intensity and the track of the Hurricane Irma vortex are successfully simulated in the 830 m scale domain (Fig. 3)
Summary
As described by Cécé et al (2016), the Lesser Antilles Arc includes small tropical islands (width lower than 50 km) where a total of 1.8 million people live, from Tobago (11.23◦ N, 60.67◦ W) to the Virgin Islands (18.34◦ N, 64.93◦ W). The Lesser Antilles are on the path of hurricanes formed over the warm waters off the coasts of West Africa and the Cape Verde islands (at 10–15◦ N latitudes), between the months of July and November. On rare occasions, they can be exposed to cyclonic storms generated in the Caribbean Sea and taking unusual west-to-east tracks as with Hurricane Omar (2008). The number of cat 4–5 hurricanes crossing closer than 50 km from the islands has doubled in the 1980–2019 period This finding is consistent with the observations of Bhatia et al (2019) for the Atlantic Ocean
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