Since El Nino is not the factor that affects the climate, none of the relationships discussed here occur every time.  What El Nino does enable us to do is to issue outlooks that favor either wetter or drier, warmer or cooler weather, than average over certain regions of the country during certain seasons.  These outlooks also say nothing about the specific variabiltiy of the weather during the season, so you're correct in that we're not able to say anything about a particular storm.  That would be a weather forecast and at this time, meteorologists are able to skillfully (not perfectly) forecast the weather out to to about 7 days.