A recurrent Pacific weather pattern known as El Nino is back in spades this year and is expected to bring some much-needed relief to drought-stricken California, research released on Tuesday shows.
California receives about 40 percent of its rainfall every year from about 10 concentrated bands, according to a newly released historical study of atmospheric rivers, which spawn the storms.
El Nino - a naturally recurring weather phenomenon that is a triggered by warming sea surface temperatures in the equatorial Pacific Ocean - doesn't impact the number of storms, but can increase their intensity, said Duane Waliser, chief scientist of the Earth Science and Technology directorate at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
See How Drought Is Changing California
Two of California's wettest years in 1982-1983 and 1997-98, occurred during El Nino events, but so did the state's two driest years, said research meteorologist Martin Hoerling, with the National Oceanic and Atmospheric Administration's Earth Systems Research Laboratory in Boulder, Colo.
The question is whether this year's El Nino, which is shaping up to be the strongest in 18 years, will be a drought-buster, Hoerling said said at the American Geophysical Union conference in San Francisco.
California has been in a drought since 2011, the driest four consecutive years on record since 1895, Hoerling said. That has left the state with a one-year water deficit.
California Drought by the Numbers
Computer simulations show that strong El Ninos do raise the prospect of more rain for California, but even an especially wet winter and spring will probably not be enough to end the state's drought, Hoerling said.
Typically, California's rainy period is from mid-December to March.
Adding to the problem is that the rains can be heavy, sparking landslides, flooding and erosion.
Near-Record El Nino Will Shake Up Winter Weather
"With the drought, the ground situation is going to be not very conducive for infiltration," Hoerling said.
"It's simplistic to talk about drought-busters as being just about rain. There's a water-resource challenge in the state that goes beyond just having a very wet, dousing rain this year," he told Discovery News.
For the eastern part of the United States, El Ninos can bring warmer-than-normal temperatures, some 4- to 5 degrees Fahrenheit higher than usual, said James Randerson, an Earth system scientist at the University of California at Irvine.
"The lack of cold air is a symptom of El Nino," he said.