Eyewall Replacement Cycle of Hurricane Matthew (2016) Observed by Doppler radar

An eyewall replacement cycle (ERC) can cause significant changes to a tropical cyclone intensity and structure, but the physical mechanisms involved in the ERC process are not fully understood due to a lack of detailed observations. Hurricane Matthew was observed by the NEXRAD KAMX, KMLB, and KJAX WSR-88D S-band polarimetric radars and NOAA P-3 airborne radar when it approached southeastern United States during an ERC event, providing a new dataset with which to better understand the ERC process. The radar observations indicate that Matthew’s primary eyewall was replaced with a weaker outer eyewall, but unlike a classic ERC, Matthew did not reintensify after the inner eyewall disappeared.

The evolution of Matthew’s ERC was analyzed by examining the observations from the airborne and ground-based radars near the Florida coast. Triple Doppler analysis was performed by combining the NOAA P-3 airborne fore and aft scanning with KAMX radar data during the period of secondary eyewall intensification and inner eyewall weakening from 19 UTC 6 October to 00 UTC 7 October. Four passes of the P-3 aircraft show the evolution of the reflectivity, tangential winds and secondary circulation as the outer eyewall became well-established. Further evolution of the ERC is analyzed through tangential and radial winds derived from the single ground-based Doppler radar observations for 35 hours from 19 UTC 6 October to 00 UTC 8 October. The Ground-Based Velocity Track Display (GBVTD) technique was utilized to diagnose the vortex axisymmetric and asymmetric kinematic structure with high temporal resolution every 6 minutes. The single-Doppler analyses indicate that the inner eyewall decayed a few hours after the P-3 flight, while the outer eyewall contracted but did not reintensify and became more asymmetric over time. The results suggest that increasing vertical wind shear played an important role in the ERC process and weakening of Matthew, leading to a different evolution than a classic ERC. Analysis of these new radar datasets will be presented to help to provide new insights into the detail of ERC process and hurricane intensity change.