A 30-m scale modeling of extreme gusts during Hurricane Irma (2017) landfall on very small mountainous islands in the Lesser Antilles

Abstract

Abstract. In view of the high vulnerability of the Lesser Antilles small islands 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 realistic 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 islands. The results pointed out that the 30-m scale seems necessary to simulate intense 400-m scale vortices leading to extreme peak gusts like 132 m s−1 over sea. Risk areas associated with terrain gust speed-up factors greater than one have been identified for the two islands. The comparison between the simulated gusts and the remote sensing building damages 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 damages and to develop safer urban management and appropriate building standards.

Storm‐Scale and Fine‐Scale Boundary Layer Structures of Tropical Cyclones Simulated With the WRF‐LES Framework

“…In the experiments, the PBL parameterization scheme is turned off in the sub‐kilometer domains and the LES technique is used. For the LES experiments, the nonlinear backscatter with anisotropy SGS parameterization scheme are used, which are consistent with model configurations in previous LES experiments (Cécé et al., 2021; Green & Zhang, 2015; Mirocha et al., 2010; Wu et al., 2018, 2019). The scheme was implemented into the WRF version 3.0 for improved LES performance at coarser resolutions and improvements in computational efficiency (Mirocha et al., 2010).…”

Responses of populations for coping with an extreme event: Saint-Martin and Saint-Barthélemy in the wake of hurricane Irma

“…The North Islands are situated in the cyclogenic basin of the North Atlantic. Before Irma, which caused 11 deaths on Saint-Martin, the last deadly hurricanes were in 1819 and 1898 (Leone et al, 2020 Very low atmospheric pressure reached up to 916hPa, with maximum sustained winds recorded at around 290 km/h (Cangialosi et al, 2018) and modelled at over 350 km/h (Cécé et al, 2020). Cyclonic surges reached 2 and 3 metres accompanied by waves of 3 to 10 metres, with maximum heights mainly affecting rocky and urbanised coasts already eroding, accentuated by the anthropisation of the coastline (Pillet et al, 2019;Rey et al, 2019).…”