If Narnia is not flat, it is certainly not spherical, as we know from VDT it has definite edges. And they are not typical edges, as they don't bend in a direction that makes sense. I think we can assume that weather systems move from West to East like they do in England (and the US). (I also seem to remember that the maps show the East to the left and West to the right, so maybe it is just the opposite, and weather comes off the sea and mobes inland East-West.) There is also a progression from south to north, with the weather (and terrain/flora/fauna) becoming more 'northerly' in the north, and more 'southerly' in the south. For the relatively compact size of the Narnian world, there is a rapid progression of climate South to North, but probably not so much East-West. There is also good evidence to support the Eastern sea area is much larger than the land area, maybe much, much larger. We know nothng about what is South of Tashbaan and even less of what is West of the Western mountains. I hope to explore some of the lands West of the Western mountains if I ever get around to finishing The Lion's Share.