12B.6 Eyewall Replacement Cycle of Hurricane Matthew(2016) Observed by Single-Doppler Radar

Tuesday, 29 August 2017: 11:45 AM
Vevey (Swissotel Chicago)
Ting-Yu Cha, Colorado State Univ., Fort Collins, CO; and M. M. Bell

Hurricane Matthew was observed by the NEXRAD KAMX WSR-88D S-band polarimetric radar when it approached southeastern United States during an eyewall replacement cycle (ERC) event. 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. The Generalized Velocity Track Display (GVTD) algorithm deduces the three-dimensional primary circulation of tropical cyclones from single ground-based Doppler radar. The GVTD technique performs a Fourier decomposition of the Doppler velocity to estimate the tangential and radial winds, which can be used to compute the vortex kinematic features. The evolution of Matthew’s ERC is documented by examining the axisymmetric primary and secondary circulations derived from the single Doppler radar observations, performing GVTD technique to diagnose the vortex kinematic structure. A NOAA P-3 flight with airborne radar simultaneously observed the internal structure of Matthew during the period of secondary eyewall intensification (17Z October 6th to 01Z October 7th). These new datasets help provide new insights into the ERC process and hurricane intensity change.
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