Spiral rainbands are such a basic part of a tropical cyclone that in most tropical cyclone basins , use of the satellite-based Dvorak technique is the main method used to determine a tropical cyclone 's maximum sustained winds . Spiral rainbands are such a basic structure to a tropical cyclone that in most tropical cyclone basins , use of the satellite-based Dvorak technique is the primary method used to determine a tropical cyclone 's maximum sustained winds .