This paper is motivated by the need to account for the impact of intermittent power output deviations by the renewable resources on dynamics of the changing electric energy systems. When uncontrolled, these deviations have the same effect as negative load variations. They are are hard to account for in small signal analysis using conventional state space (CSS) models. In this paper we illustrate the new transformed state space (TSS) model which represents power dynamics as a state variable. We use the Kundur two area 4 generators test system to illustrate the new model, perform its eigenmode analysis and compare with the spectral properties of the CSS model. We illustrate how the explicit modeling of power dynamics sets the basis for fundamental understanding of eigenmode structures for disconnected areas and for the interconnected system. Given these properties, we suggest that interarea dynamics can be monitored by measuring power deviations, and does not require PMUs, a major simplification. It is also illustrated how these dynamics can be monitored using just these power deviations on a commonly used two area test system.