The intrinsic error growth in a large-domain Eta Model is investigated over the North Pacific and the North Atlantic using fixed boundary conditions. It is first shown that the dependence of the intrinsic instability properties of the flow on the particular boundary conditions (provided by global atmospheric analysis) is weak in summer and in winter (although it is more pronounced in winter). The analysis does not reveal substantial differences for the short-term error growth between the two regions investigated, suggesting that both regions display similar dominant instability properties. Finally, the spatial distribution and amplification rate of the error are very close to the ones found in global atmospheric models. These findings indicate that, as far as the dominant instability properties are concerned, the dynamics of this model version display strong similarities with the synoptic-scale dynamics of global models and are weakly sensitive to the choice of (fixed) boundary conditions.