Hurricane track trends and environmental flow patterns under surface temperature changes and roughness length variations

Abstract

Given the significant damage that hurricanes can cause every year, accurate forecasts of these extreme weather events are crucial. Ocean warming can substantially impact the intensity and track of hurricanes in the future. Forecasting the track of hurricanes is typically more challenging than intensity predictions since tracks are influenced not only by hurricane vortex dynamics but also by global and synoptic weather systems (i.e., environmental flow). The dynamical mechanisms that modulate hurricane trajectories under changes in the surface temperature and friction are not comprehensively established yet. The primary objective of this paper is to address this knowledge gap by conducting six real hurricanes and some non-hurricane simulations using the Weather Research and Forecasting (WRF) model. In total, 90 WRF simulations are carried out to characterize the impacts of varying the surface temperature and drag on hurricane tracks and their relationship with environmental flow patterns. It is found that ocean warming tends to intensify hurricanes by ∼20 % and decrease their azimuthal translational velocity, and vice versa when the surface is cooled. Hurricanes move more towards the west over the Atlantic Ocean when the surface temperature is decreased and vice versa. This was shown to be due to the changes in the average azimuthal speed of environmental flows. Increasing the surface temperature, destabilizes the atmosphere, and increases the surface friction velocity. Hence, increased surface friction appears to slow down the environmental flow and consequently hurricane track azimuthal translational speed. This finding was confirmed by another suite of simulations in which only the surface roughness length of the low-wind environmental flow regime was altered. It was shown that surface drag changes have a similar impact on hurricane tracks as surface temperature variations. Decreasing the default surface drag for low-wind regimes tends to further move the hurricanes toward the west and vice versa. This paper provides notable insights into future hurricane track trends and the role of ocean temperature and momentum exchange coefficients in hurricane track and environmental flow patterns. Moreover, the results of this study can be useful for advancing surface layer parameterizations and their impacts on hurricane track forecasts in weather/climate models.