Eye and Eyewall Radii and Track of Typhoon Trami (2018) Derived From Advanced Himawari Imager (AHI) Brightness Temperature Observations.

The center positions and sizes of tropical cyclones (TCs) are very important for monitoring and forecasting their track and intensity changes. Brightness temperature (TB) observations of geostationary satellite imagers have high temporal and spatial resolutions and can thus reflect cloud and rain structures within and around TCs. In this article, an objective method is developed to determine the center positions and eye and eyewall radii based on Advanced Himawari Imager (AHI) TB observations at channel 13 (10.45 mu m) from the Japanese geostationary satellite Himawari-8. Results show that the positioning deviation of AHI-determined centers of Typhoon (TY) Trami from the best track from the Joint Typhoon Warning Center (JTWC) is smaller when TC intensity is stronger. The average deviation of the center positions is 28.18 km. The accuracy of the proposed method is validated by the results of ten other TYs in the Northwest Pacific during August and September 2018. The AHI-determined radii of both eye and eyewall match well with the characteristic distributions of clouds and rainbands near the center of Trami. During the rapid intensification (RI) of Trami, Trami centers are characterized by low-values TBs that have an elliptical shape rotating counterclockwise with time. This may reveal a possible existence of vortex Rossby waves with azimuthal wavenumber 2. The TC center position and eye and eyewall radius parameters obtained from the TB observations of the geostationary satellite imager could be applied to an advanced vortex initialization to improve TC track and intensity forecasts.