A weather-altering El Niño is increasingly likely to develop in the Pacific Ocean later this year, according to a U.S. government forecast issued Thursday.
National Oceanic and Atmospheric Administration meteorologists now believe an El Niño has a 66% chance of forming by this winter.
If the prediction materializes and the influential climate pattern sets in, it could bring wetter weather to California and the southern U.S., suppress the Atlantic hurricane season and compound global warming by boosting temperatures in 2015.
Government forecasters say observations and computer models in recent weeks indicate that water below the surface in the eastern tropical Pacific Ocean is warming and showing increasing signs that an El Niño is afoot.
“The odds are increasing but still not one hundred percent,” said Mike Halpert, acting director of NOAA's Climate Prediction Center.
After inching slowly upward, the chances of an El Niño surpassed 50% last month, prompting NOAA activate its alert system and issue an official El Niño watch.
A forecast by Australia's Bureau of Meteorology on Tuesday predicted a 70% chance of an El Niño in the coming months.
The naturally occurring climate cycle occurs every two to seven years when weak trade winds allow warmer surface water to pile up along the west coast of South America, shifting storm activity and altering precipitation patterns around the globe.
Though El Niño is associated with above-average rainfall in the southern U.S. and Southern California, its return would not be a guaranteed drought-buster.
A potent El Niño in the winter of 1997-98 doubled rainfall in Southern California, but other episodes, including strong El Niños in 1965-66 and 1991-92, resulted in below-normal rainfall.
The pattern has been in a lull for the last two years, with the eastern Pacific never warming enough to form a El Niño or cooling to generate a La Niña. The last El Niño, in 2009-10, was moderate and followed by the cool-water phase, La Niña.
NOAA's latest forecast gives a 30% likelihood of conditions remaining neutral by year's end and a 4% probability of a La Niña.