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

The eyewall replacement cycle (ERC), which typically has three distinctive phases including intensification, weakening, and reintensification, often occurs in intense TCs. In addition to the intensity change, an ERC is usually accompanied by a broadening of the wind field. The expansion of the tangential wind field due to the inward advection of absolute angular momentum results in increasing radial inflow outside of the primary eyewall and developing supergradient winds near the top of the inflow boundary layer. The imbalance of pressure gradient and centrifugal force associated with supergradient winds can strengthen and manifest the deep convection in this region leading to secondary eyewall formation. After the development of a concentric eyewall, the tropical cyclone often undergoes a replacement cycle where the inner eyewall is replaced by the outer eyewall.

Hurricane Matthew was observed by the NEXRAD KAMX WSR-88D S-band polarimetric radar when it approached southeastern United States during an ERC event. It is one of the most destructive and long-lived hurricanes in recent years. In this study we use single Doppler radar with high temporal resolution to retrieve the kinematic structure of Matthew derived from the ground-based velocity track display (GBVTD) technique. The evolution of Matthew’s ERC is documented by examining the axisymmetric primary and secondary circulations deduced from the radar observations. A NOAA P-3 flight with airborne radar simultaneously observed the internal structure of Matthew during the period of secondary eyewall intensification (17Z October 6^th to 01Z October 7^th). These new datasets help provide new insights into the ERC process and hurricane intensity change.