We all got burned last year after weather people got us all psyched up for a wet El Niño winter to alleviate some of the drought, and then it never came. (Well, it actually did come, but basically not until March, and it was weak enough as to be basically useless.) But it's happening again: The Pacific is warming, and federal forecasters are making predictions for a strong El Niño again, saying, "No really, it's almost definitely happening this time."
As SFGate reports, "the National Oceanic and Atmospheric Administration pegged the chances of an El Niño at 60 to 70 percent through 2015." The prediction comes from this report, and they're saying the 60-percent figure is the chance that the warming trend will continue through the fall, and therefore influence precipitation in our West Coast winter.
Just to explain, for California newbies: An El Niño winter happens as a result of particularly high warming in the Pacific Ocean and lasts from December to April and during severe El Niño years, it can mean an endless stream of rain for several months. There are also what's called La Niña years, when cooler waters also influence our weather, and you can read this partial explanation we gave during the last La Niña winter in 2010-11.
This past winter, along with the winter of 2009-10, were weak to moderate El Niños. The last real El Niño year with truly significant rainfall was in 1997-98, and since then we've had also had five weak, cooler La Niña years. But as we saw last year, it's hard to predict this far out what we're truly in for.
Also, as Stanford PhD candidate in climatology Daniel Swain explains, "It’s not a slam-dunk drought-buster by any means," it's just that historically speaking, when robust El Niño trends happen, we tend to have wetter winters.
That is all. Don't get excited yet.