Hi Erik, thanks for the comment! A lot went into why southern California did not receive as much rain as expected and it is probably too soon to point to any one cause. There likely will be plenty of research into exactly what happened. What makes attribution difficult is that we do not have a long list of El Ninos like the most recent to compare impacts to. What was just seen could simply be a potential natural outcome during a strong El Nino or highlight the randomness of weather. This is one reason why forecasts for winter rainfall for southern California peaked at around 65% chance for above-average rains.