A Modeling Study of the Principal Rainband in Hurricane Matthew (2016) during Its Intensification in the Caribbean

This study explores the topographic influences on tropical cyclone (TC) rainband structure in Hurricane Matthew (2016) to examine if and how remote topography can impact the strength of convection, with a specific focus on a robust convective feature east of the TC center during the storm’s rapid intensification in the southern Caribbean Sea. We utilize the Advanced Research Weather and Research Forecasting Model (WRF-ARW) to compare the TC structure in a control simulation (CTL) with that in an experimental simulation with topography reduced by 50% over South America (T50). We anticipate the long-lived convective feature is associated with the principal rainband within the stationary band complex. To evaluate this hypothesis, we calculate inertial stability and identify a threshold for delineating inner rainbands from outer rainbands. We also utilize WRF-STILT to create backtrajectories to ascertain the origin of airstreams and further evaluate the inner core structure. Next, we evaluate the T50 simulation to determine how reduced topography impacts the thermodynamic and dynamic profiles near and upstream of the long-lived convection. We also compare the horizontal wind and divergence fields associated with the TC rainbands in these two simulations. Downslope winds off of the South American terrain are expected to modify the thermodynamic profile and the kinematic structure in the vicinity of the stationary band complex. This, along with moderate westerly shear, is the anticipated reason for the robust convection in Hurricane Matthew. Outcomes of this study include an improved understanding of the principal rainband in Hurricane Matthew and, more broadly, the forcing mechanisms for robust TC rainbands, which will aid in improving precipitation forecasts in tropical cyclones.