A Modeling Study of the Principal Rainband in Hurricane Matthew (2016) and the Influence of Remote Terrain on Hurricane Structure During its Intensification in the Southern Caribbean

Hurricane Matthew (2016) was a category 5 hurricane that interacted with remote terrain over northern South America in the early stages of its life cycle. Because tropical cyclone (TC) precipitation and convection are known to be crucial factors in the understanding and forecasting of TC intensity, this study investigates how this terrain impacted Hurricane Matthew’s rainband structure. Remote terrain is hypothesized to play a role in the strength of TC rainband convection by modifying the thermodynamic environment such that subsiding dry air advects over an extremely moist ocean surface layer leading to increased moist static instability. To investigate this hypothesis, this study utilizes the Advanced Research Weather and Research Forecasting Model (WRF-ARW) version 4 to create a high-resolution (2-km horizontal grid spacing) control simulation (CTL) of Hurricane Matthew and three experimental simulations with 125% (T125), 75% (T75), and 50% (T50) changes to terrain height over the topography of northern South America. Additionally, we utilize two boundary layer parameterization schemes. This study focuses on a particular convective rainband positioned downstream of the terrain that displayed prolonged robust convection during the initial stages of Hurricane Matthew’s life cycle. Results indicate that characteristics of this robust rainband are consistent with prior research on the principal rainband. In the experimental simulations, this rainband displays minor differences in intensity and position and is more persistent in the simulations with higher terrain. In the region downstream of the topography, significantly (p < 0.05) drier conditions exist in the CTRL and T125 simulations, which is consistent with the hypothesis that downslope motion would lead to a drier air mass. TC structural changes are also apparent, with a weaker TC in the reduced topography simulations. This research emphasizes the potentially important role of distant terrain on TC structure. In particular, this study identifies downstream influences on TC rainband convection and warm core structure. Conclusions of this research are limited due to the small sample size of a single case study. An ensemble modeling study and additional cases are needed for a more thorough conclusion on the impact of remote terrain on TC structure.