Disclosed embodiments include systems and methods for estimating real-time bit forces experienced on a drill bit and decoupling bit force disturbances. Real-time bit forces can be estimated based on bit force observers using measurements from downhole sensor subs. Model-based observers that adopted to estimate the bit force from downhole sensor sub measurements. Strain and torque measurements as measured by the sensor subs are used to estimate bit force and bit torque. These measurements can be observed using an effective observer design with the estimated bit force and bit torque based on sensor sub measurements to track the real bit force and bit torque. Observations of estimated bit forces and identified bit force disturbances can be used perform drilling dynamics modeling and identify the occurrence of negative drilling events.