GOES-16 ABI Brightness Temperature Observations Capturing Vortex Rossby Wave Signals during Rapid Intensification of Hurricane Irma (2017)

Abstract

Geostationary Operational Environmental Satellite-16 (GOES-16) Advanced Baseline Imager (ABI) observations of brightness temperature (TB) are used to examine the temporal evolutions of convection-affected structures of Hurricane Irma (2017) during its rapid intensification (RI) period from 0600 to 1800 UTC 4 September 2017. The ABI observations reveal that both an elliptical eye and a spiral rainband that originated from Irma’s eyewall obviously exhibit wavenumber-2 TB asymmetries. The elliptical eye underwent a counterclockwise rotation at a mean speed of a wavenumber-2 vortex Rossby edge wave from 0815 to 1005 UTC 4 September. In the following about 2 hours (1025–1255 UTC 4 September), an inner spiral rainband originated from the eyewall and propagated at a phase speed that approximates the vortex Rossby wave (VRW) phase speed calculated from the aircraft reconnaissance data. During the RI period of Irma, ABI TB observations show an on–off occurrence of low TB intrusions into the eye, accompanying a phase lock of eyewall TB asymmetries of wavenumbers 1 and 2 and an outward propagation of VRW-like inner spiral rainbands from the eyewall. The phase lock leads to an energy growth of Irma’s eyewall asymmetries. Although the eye remained clear from 1415 to 1725 UTC 4 September, an inner spiral rainband that originated from a large convective area also had a VRW-like outward propagation, which is probably due to a vertical tilt of Irma. This study suggests a potential link between convection sensitive GOES imager observations and hurricane dynamics.