Simplify the following text for a Grade 13 native English-speaking person.
Original: 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 .
Simplified: 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 .