Well, its a factor...like everything else. As a starting point, its common sense to first consider La Nina seasons if expecting a La Nina......but obviously these outlooks are getting more difficult becasuse there are an increasing number of forces at play as a result of CC. Its funny because on the one hand, its easier since 9/10 seasons are biased warm...but the catch is that its getting more difficult to get the rationale for the warmth right within the context of a given season, aside from the background CC trend. For instance, most of predicted warmth simply because of a canonical strong El Nino were not right.