Impacts of Mesovortices on the Evolution of Hurricane Harvey (2017)

During the landfall of Hurricane Harvey (2017) near Rockport, TX a C-band Shared Mobile Atmospheric Research and Teaching (SMART) radar coordinated with the NWS WSR-88D in Corpus Christi, TX (KCRP) to provide dual-Doppler wind retrievals of the hurricane structure during landfall. Data were collected every 5 minutes for nearly 19 hours. A portion of the wind retrieval domain extended over the Gulf of Mexico, providing an opportunity to compare processes observed over water and over land.

The analyses reveal several key aspects of tropical cyclone (TC) evolution, which are often difficult to observe in high temporal resolution. First, the evolution of the inner core from approximately 22 UTC on 25 August 2018 to 00 UTC on 26 August indicates that outward propagating vortex Rossby waves (VRWs) resulted in partial symmetrization of Harvey’s primary (symmetric) circulation prior to landfall. However, due to to the eyewall’s interaction with land, Harvey again became asymmetric, displaying multiple mesovortex structures propagating along the inner edge of the eyewall. The mesovorticies locally enhanced the 500 m wind field near the radius of maximum wind by 5-10 m s^-1. Surface observations collected by in situ platforms throughout the dual-Doppler domain suggest that these mesovortices also enhanced near surface winds. In addition, previous literature has suggested that mesovortices and VRWs may result in the redistribution of momentum in the inner core. Observational evidence for the excitation of outward propagating VRWs and resultant inner core momentum redistribution by these mesovortex/eyewall VRW structures will be shown. The significance of these results will be presented in context of both impacts to the coast at landfall and TC evolution.