A disclosed vibration monitoring method includes: processing sensor information downhole to detect one or more vibration modes; responsively updating a vibration mode state machine; communicating a current machine state to an uphole module; deriving from said current machine state at least a primary vibration mode and associated severity; and modifying at least one drilling parameter if the severity exceeds a threshold. A disclosed drilling system implementation includes: a drill string; a rig or other deployment device that conveys the drill string into a borehole using at least one controllable drilling parameter; one or more downhole sensors providing vibration-related signals; a downhole processor that operates on the vibration-related signals to detect one or more vibration modes and responsively updates a vibration mode state machine; and an uphole module that receives the current state from the downhole processor and derives from the current state at least a primary vibration mode and severity.