A tropical storm is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between 34 knots ( 39 mph ) and 64 knots ( 74 mph ) .
A tropical storm is an organized system of strong thunderstorms with a very clear surface circulation and maximum sustained winds between 17 and 32 m\/s ( 34-63 kt , 39-73 mph , or 62-117 km\/h ) .