Let the hype begin. CPC has issued an El Nino Watch for the 50% possibility of a weak El Niño next fall from the IRI/CPC forecast ensemble. A similar Watch was issued in 2012 but El Niño never materialized.
Already there are headlines about El Niño being the answer to California's drought which only perpetuates the myth that El Niño definitely means lot of rain for California. To put aside this and some of the more prevalent misconceptions see The Myths and Realities of El Niño.
The bottom line is that climatology should NOT be used as a forecast tool. An "average" El Nino is made up of a very broad range of past events!