After three years of drought in California, weather gurus are talking about the appearance of El Niño in the Pacific Ocean, raising hopeful memories of drenching winters.
Unfortunately, it might not be that kind of El Niño.
Scientists say it is too early to predict what the phenomenon, a huge blob of warm water at the equator, might mean for California. But many climate researchers suggest it won't be strong enough to influence predictions of a wet winter.
"It is likely that this winter will feature moderate El Niño conditions," said climate researcher Dan Cayan of the Scripps Institution of Oceanography in La Jolla.
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A moderate or weak El Niño means the water blob warms only a degree or two. But the water must rise 3 to 5 degrees to become a strong factor in wet- weather predictions. Such a strong El Niño hasn't happened since 1998.
If only moderate or weak ocean warming takes place, many scenarios could fit the forecast, including another drought year.
"That's one reason I'm not jumping up and down," said meteorologist Jan Null, who runs a weather-consulting business in Northern California.
Still, it's the first hint of good weather news in years for California, where a $36 billion farm industry is idling thousands of acres because of drought and water cutbacks for threatened fish species.
Water rationing is becoming a regular topic in Los Angeles and San Francisco.
Temperatures near the surface of the Pacific are rising noticeably for the first time since 2006. It is the classic profile of El Niño, which is Spanish for "the boy," referring to the Christ child because of its usual onset in winter. The phenomenon occurs when westward-blowing trade winds weaken, allowing warm water in the western Pacific to spread thousands of miles eastward toward the coast of South America. It happens every three to seven years.
The warm water and shifting wind can influence Pacific storms to move toward the southwestern United States. Southern California often can receive above-average rainfall while the Pacific Northwest dries out.
Scientists track El Niño using buoys with sensors all over the equatorial Pacific, recording water temperature, humidity, wind speed, precipitation and other data. The information is analyzed with computer models designed to describe and predict weather.
Droughts to hurricanes
El Niño has been blamed for droughts in Indonesia and credited for suppression of hurricanes in the Atlantic Ocean.
In California, a very strong version of the phenomenon was lurking in the Pacific in 1982-83 when the state had its biggest storm totals on record.
Modesto's biggest seasonal rainfall total, more than 26 inches, occurred that year. Such strong El Niño events do not happen often.
Is there a chance El Niño will be strong this winter? Yes, but it is small, if forecast models are correct.
Of the climate research groups forecasting El Niño, only a few predict it will be very warm by January. Most scientists suggest moderate warming.
The 2006-07 El Niño was considered weak, and Modesto had 8.36 inches of rain. The last moderate El Niño was in 2002-03 when Modesto had 9.4 inches of rain, shy of the city's 12.21-inch average.
The last time Modesto had above-average rainfall during El Niño was in 1997-98. The city had more than 24.6 inches.
"We'll have to wait until November to get a better idea," said meteorologist Elissa Lynn of the California Department of Water Resources in Sacramento. "But if it's moderate or weak, it may not help our forecasting."