Multi-Doppler Radar Analysis of Hurricane Matthew’s Eyewall Replacement Cycle

In a tropical cyclone eyewall replacement cycle (ERC) a secondary concentric eyewall forms from rainbands, and eventually replaces the original eyewall at a larger radius. The ERC process often occurs in a mature tropical cyclone, but the physical mechanisms by which this process occurs are still not well understood. Hurricane Matthew (2016) underwent an ERC near the Florida coastline, and observations from both the NOAA WP-3D’s Tail Doppler Radar (TDR) and Miami’s NEXRAD ground based radar simultaneously allowed for a triple Doppler analysis of the inner core. This level of coverage was maintained for four consecutive Hurricane Hunter passes as the secondary eyewall of Matthew was strengthening and the primary was decaying. Although this period of an ERC is typically followed by reintensification, Matthew began to weaken at this stage due to vertical wind shear. The Doppler Radar data available for Matthew during the study period was quality controlled and processed using LROSE (Lidar Radar Open Software Environment). Analysis was carried out by combining all available Doppler radar data using SAMURAI, a 3D variational technique. The resulting analysis provides insight into the evolution of Matthew’s secondary circulation. An expansion of Matthew’s primary circulation was evident when examining the tangential wind field. The radial winds showed blocking of inflow to the primary eyewall and the decay in the primary which likely stemmed from the lack of inflow. A filling of the moat region throughout the four passes was also observed. Continued evolution of the ERC as Matthew moved up the Florida coast was analyzed using the single-Doppler VORTRAC analysis software, providing additional insight into how vertical wind shear affects the secondary eyewall and overall evolution of an ERC.