New theoretical concepts and machinery derived from information theory are used to examine mid-latitude ensemble predictability of the atmosphere. In particular the focus will be on the the nature of variations in statistical predictability. In the second part of the talk we examine preliminary results on the effects of coherent tropical convective disturbances on mid-latitude predictability. Disturbances such as the Madden Julian Oscillation exhibit a broad spectral peak at a period of several weeks. This suggests that better depiction of such phenomena in NWP models may improve global atmospheric predictability on long times scales.