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

The principal rainband (PRB) is a primary band within a stationary band complex (SBC) extending outward from the eyewall, and its location and intensity have implications on the location of heavy precipitation within a hurricane. This is evident in Hurricane Matthew (2016) as the tropical cyclone strengthened in the southern Caribbean Sea. In particular, the convection within Hurricane Matthew’s PRB was robust and noted in real-time as potentially atypical. This study explores the topographic and wind shear influences on Hurricane Matthew’s PRB to examine if and how these variables impacted the strength of convection. Downslope winds off of the South American terrain are expected to have an influence on the moisture convergence in the region of the PRB in Hurricane Matthew. This, along with strong low-level easterly flow, is the anticipated reason for the robust convection in the PRB. To analyze this, we utilize the Advanced Research Weather and Research Forecasting Model (WRF-ARW) to first run a control simulation and then compare the control simulation to two model simulations: 1) with topography reduced by 50% over South America and 2) with low-level winds reduced in the strong easterly flow to the east of the tropical cyclone. Within the model environment, we evaluate modifications to the wind field and related confluence associated with the PRB. Outcomes of this study include an improved understanding of the PRB in Hurricane Matthew and, more broadly, the forcing mechanisms for robust convection in PRBs, which will aid in improving precipitation forecasts in tropical cyclones.