It was the big tease of 2014.
Scientists reported that El Niño conditions were shaping up in the Pacific Ocean, potentially bringing winter rains that could end California’s historic drought. But then it all fizzled. Now, scientists say, El Niño is back — and perhaps more promising.
On Thursday, the National Oceanic and Atmospheric Administration announced that the probability of El Niño conditions being present through the end of 2015 is now 80 percent — up from 60 percent last month and 50 percent the month before.
Ocean temperatures at the equator near South America are even warmer now than at this time last year, researchers say, and they appear to be triggering the kinds of early changes in the atmosphere that can lead to strong El Niño conditions that historically have been linked with a higher likelihood of wet winters for California.
Does this mean the drought is going to end by next Christmas? Time to break out the galoshes?
It’s too early to tell, experts say.
“We’re seeing this evolve in a way that could increase the odds that next winter would be wet,” said Mike Halpert, deputy director for NOAA’s climate prediction center in College Park, Maryland.
“Things are trending the right direction,” he said. “But no promises. Winter is still a long way off. What we’re seeing so far is good news. But don’t stop conserving water yet.”
Last year, despite all the encouraging signs, warmer-than-normal ocean temperatures did not connect properly with the atmosphere to generate big storms, and the drought worsened.
Generally speaking, El Niños begin when trade winds that normally blow westward, toward Asia, weaken, and then blow the other way. That allows warm Pacific Ocean water near the equator to spread east, toward South America. Rainfall follows the warm water, which can mean wet winters for California, Peru and other areas, and droughts for Australia.
The opposite, or a cooling of the ocean water, is called “La Niña.”
The term El Niño — or “little boy” in Spanish — was originally used by fishermen along the coasts of Ecuador and Peru to refer to “the Christ child” because the phenomenon appeared every three to eight years around Christmas.
In March, NOAA scientists using satellites, buoys and other devices to measure ocean temperatures declared that El Niño conditions were present. Since then, ocean surface temperatures have continued to warm and are now about 1.8 degrees Fahrenheit warmer than the 1981-2010 average along the equator near South America. That’s twice as much above the average as last year.
Meanwhile, trade winds blowing east toward North America are present, a key component for sustaining El Niño conditions, NOAA says. They weren’t present last year, which is why the whole trend fizzled.
Supercomputers at NOAA, NASA and other world-leading scientific institutions that are modeling the changing conditions project that there is a 2-in-3 chance that the average ocean surface temperature on the equator off South America will be about 4 degrees warmer than the historic average by the end of 2015.
If those projections prove accurate, that would mean a strong El Niño is present. During the biggest El Niño winters, in 1997-98 and 1982-1983, Pacific waters reached nearly 5 degrees warmer.
But all El Niños are not created equal.
Generally speaking, the warmer the ocean water during El Niño years, the greater the likelihood of heavy winter rainfall, and even flooding, in California. During mild El Niño years, when the ocean water is only slightly warmer than historic averages, there are just as many drier-than-average winters in California as soaking ones.
Since 1951, there have been six winters with strong El Niño conditions. In four of them, rainfall from the Bay Area to Bakersfield was at least 140 percent of the historic average, according to studies by Saratoga meteorologist Jan Null.
But in the 16 winters since 1951 when there was a weak or moderate El Niño, California experienced below-normal rainfall in six of them. There was average rainfall in five and above-normal precipitation in the other five.
Although the Pacific is in a growing El Niño pattern now, it could peak and dissipate, experts say. And after last year’s bust, they are urging caution, particularly as Californians in a fourth year of drought are increasingly desperate for some good news.
“This is promising. But don’t cash in your 401(k) and invest in umbrellas yet,” said Bill Patzert, a research scientist and oceanographer at NASA’s Jet Propulsion Laboratory in Pasadena.
“The winter is still six months off. We have a while to see what develops. If anybody tells you it is a sure thing, they are pulling your leg.”
Bay Area water officials also are trying to tamp down enthusiasm, largely because they need to preserve water supplies in case the drought drags on into 2016 or 2017.
“The drought isn’t over until our reservoirs are full,” said Abby Figueroa, a spokeswoman for the East Bay Municipal Utility District. “That might take more than one wet winter.”
Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN
