Investigating the interaction of tropical cyclone-heatwave compound hazards in urban environments

While tropical cyclone (TC) and heatwave (HW) compound hazard extremes are rare in the historical record, they have been recently emerging and are expected to become more frequent under future climate projections. Joint TC-HW hazards can exacerbate heat stress felt by residents, particularly in densely populated urban communities or areas suffering from storm-related power outages. The Princeton Urban Canopy Model (PUCM) has been used to evaluate heatwave conditions in urban environments, but has yet to be used to model joint TC-HW conditions. In this study, we model joint TC-HW hazards by adjusting the surface energy and water budgets of the PUCM to account for TC flood and extreme wind hazards. We investigate joint hazard interactions during Hurricane Laura (2020) using the Weather Research and Forecasting model (WRF) to simulate both Laura's wind field to drive subsequent hydrodynamic modeling of inundation and post-storm atmospheric conditions. The WRF and hydrodynamic modeling results are then used to drive the PUCM to assess the interaction of joint flooding, wind, and heat and their impacts on the city of Lake Charles in Louisiana. Results show that accounting for TC inundation up to a week after landfall can cause over 3°C reductions in daytime heat stress and 1.5°C increases in nighttime heat stress compared to simulations that ignore the presence of flooding. Accounting for defoliation from extreme TC winds can increase maximum nighttime heat stress by more than 4°C. • Novel framework models urban compound hurricane-heatwave interactions at the block scale. • Hurricane hazards can reduce daytime and exacerbate nighttime urban heat stress. • Calculations of compound pedestrian heat stress are highly sensitive to metric selection.