For anyone interested in El Nino impacts on CA weather, this is a great place to start: NWS CA Briefing.  Our knowledge of El Nino impacts on CA is limited by 1) a lack of understanding of direct links between individual storms and El Nino and 2) a lack of exposure to extreme El Nino events like the one forecast for this winter.  From a planning perspective, it clearly makes sense to consider that a strong El Nino might bring strong, rainy storms to CA.  But, given that El Nino will not fundamentally alter the fact that in CA we are affected each winter by a relatively small number of cyclones, it is way too early to imagine the worst.