Well, if you think about it....the argument is that global warming is is having a muting effect on warm ENSO events....my train of thought is why would that not serve to augment cool ENSO events.
I get that shorter term stochastic fluctuations are more relevent with regard to storm potential, but that doesn't negate the value of monthly aggregate calculations ...especially at longer, seasonal lead times. And while volatility of the polar fields is paramount with respect to optimizing winter storm potential, I would rather have a static negative node and positive.