You’ll hear a lot about El Nino this year.
The term refers to warmer-than-average waters in the equatorial Pacific that can affect weather around the world, increasing the likelihood of severe drought in some areas and torrential rains in others. Indicators are increasingly suggesting that such an event will develop late this summer, and it is possible that it could be the strongest event in a century to affect Southern California.
This possibility is lighting up meteorological forums and bursting into mainstream consciousness with the European Center for Medium-Range Weather Forecasts issuing an outlook this week indicating that sea surface temperatures could reach 2 degrees Celsius above seasonal averages. The chance of that happening by late autumn stands at 1 in 4, according to a forecast released Thursday by the National Oceanic and Atmospheric Administration.
Some people call El Niños Super El Niños that exceed this threshold of warming – relatively rare events that are more likely to produce widespread impacts. “This is essentially the upper echelon of El Niño events,” said U.S. Forest Service meteorologist Jonathan O’Brien.
El Niño is a phase of a recurring global cycle known as the El Niño–Southern Oscillation, whose counterpart is La Niña. This cycle occurs when changes in tropical wind patterns – or trade winds – allow vast stores of sun-baked seawater to move eastward across the Pacific and toward the Americas.
This unusually warm water typically releases heat into the air, adding to global temperatures already rising due to climate change from burning fossil fuels. Experts say it could also alter polar and tropical jet streams, sending storms on the way to Southern California and the southern United States.
The amount of warm water available for this year’s event exceeds that of 1997-98, which was one of the strongest El Niño events of the century, said Paul Roundy, a professor of atmospheric sciences at the University at Albany.
That winter, a series of storms caused flooding and debris flows across California, destroying homes, washing out roads, and killing 17 people. Around the world, a typhoon in Acapulco killed hundreds and Indonesia recorded one of the worst droughts on record.
“If the signals continue to develop as they are currently, it’s possible we could have an even stronger event than 1997,” Roundy said. They estimate that this year’s El Nino is stronger than any other since the 1870s, when drought killed an estimated 30 million to 40 million people in India, China and Israel.
The latest NOAA Outlook released Thursday projects a more than 90% chance that El Niño will develop by the fall and a 50% chance that it will be at least a strong event, said Nathaniel Johnson, a meteorologist with NOAA’s Geophysical Fluid Dynamics Lab and a member of its El Niño-Southern Oscillation seasonal forecast team.
The change could be rapid, he said, adding that some research suggests climate change is contributing to more frequent, extreme shifts from La Niña to El Niño.
But even when strong El Niños develop, they don’t always translate to the weather conditions people expect.
In 2015-16, a Super El Niño was predicted — dubbed a Godzilla El Niño by some forecasters — but California’s annual precipitation totals remained around average, said state climatologist Michael Anderson.
Traffic on flooded Interstate 5 is limited to one lane in each direction as Caltrans workers attempt to clear drains and restart pumps in Sun Valley on January 6, 2016.
(Brian van der Brug/Los Angeles Times)
But in 1982–83, when another Super El Niño occurred, the hurricane destroyed several ferries and destroyed a 400-foot section of the Santa Monica Pier. He said the state’s rainfall later in the year will be determined more by factors, such as the frequency and strength of atmospheric rivers, rather than whether it is technically an El Nino year.
In Southern California, a strong El Niño increases the likelihood of a wet winter that replenishes water supplies and reduces wildfire risk but could also increase flooding, debris flows, and coastal erosion. Still, it is impossible to predict the exact effects.
O’Brien, a meteorologist with the U.S. Forest Service, said El Nino typically strengthens the subtropical jet stream, meaning much of California’s weather in the fall and winter months comes from the south, as opposed to the north, which brings warm air with more moisture.
This could help limit Southern California’s wildfire potential in the fall and winter, which is typically shaped by the presence of Santa Ana winds. O’Brien said El Nino increases the likelihood of early winter rains, which could reduce the risk of winds that fuel fires.
“We are completely optimistic that we will have rain in the fall, which will keep the Santa Ana winds at bay and limit our potential chances for next year’s fall and winter months,” he said.
Still, much uncertainty remains.
Tim Stockdale, lead scientist at the European Center for Medium-Range Weather Forecasts, wrote in an email that the climate system in the tropical Pacific in March and April is inherently less predictable, and even the most advanced models may struggle to understand how conditions will evolve. The picture generally becomes more clear between late May and June, he said.
But it’s not just land-dwelling creatures that have to keep an eye on El Nino.
The pattern, which can reduce the nutritional quality of plankton, is believed to have intensified the effects of an unusually warm blob of seawater along the California coast that continued from 2013 to 2016, resulting in the mass die-off of sea lion pups whose starving mothers were not able to produce enough milk to sustain them.
According to Giancarlo Rulli, associate director of public relations for the Marine Mammal Center, sea lion breeding and pup season is fast approaching in key reefs like the Channel Islands. “Experts are monitoring current oceanographic reports with a healthy level of concern,” he wrote in an email.
Times deputy managing editor Monte Morin contributed to this report.
