California may be on track for a ‘good’ El Niño. It can bring rain, floods, coastal erosion

You will hear a lot about El Niño this year.

The term refers to warmer-than-average waters near the equatorial Pacific that can influence global climate, increasing the likelihood of tropical droughts in some regions and heavy rain in others. Indications are increasingly suggesting that such an event will develop later this summer, and may be the strongest this century to affect Southern California.

This hope has been lighting up the climate forums and was seen by many people this week with the release of the opinion of the European Center for Medium-Range Weather Forecasts which shows that the sea temperatures may exceed the seasonal average by 2 degrees Celsius. The latest forecast released Thursday by the National Oceanic and Atmospheric Administration puts the odds of that late fall at 1 in 4.

Some call El Niños that exceed this threshold warming El Niños — relatively rare events that can produce varying effects. “It’s basically an El Niño event,” said Jonathan O’Brien, a meteorologist with the US Forest Service.

El Niño is one phase of a recurring global cycle known as the El Niño-Southern Oscillation, and its counterpart is La Niña. This cycle occurs when changes in tropical air patterns – or trade winds – allow large amounts of sun-baked ocean water to move eastward across the Pacific and up against the Americas.

These unusually warm waters tend to release heat into the atmosphere, rising global temperatures that are already rising due to climate change due to the burning of fossil fuels. It could also alter the tropical and subtropical jet streams, sending storms on a path across Southern California and the southern United States, experts said.

The amount of warm water available for this year’s event exceeds that of 1997-98, which was among the strongest El Niño events of the century, said Paul Roundy, a professor of atmospheric science at the University of Albany.

That winter, a relentless series of storms caused flooding and debris in California, destroying homes, flooding roads and killing 17 people. Around the world, the storm killed hundreds in Acapulco and Indonesia recorded its worst drought in history.

“If the signal continues to develop as it is now, we may have reached a stronger event than 1997,” said Roundy, who predicts about a 20 percent chance that this year’s El Niño will be stronger than any other since the late 1870s, when an estimated 30 to 40 million people died of drought in India, Israel and Israel.

NOAA’s latest outlook, released Thursday, predicts a more than 90% chance that El Niño will strengthen by fall and a 50% chance that it will be at least a strong event, said Nathaniel Johnson, a meteorologist at NOAA’s Geophysical Fluid Dynamics Lab and a member of its seasonal El Niño-Southern Oscillation team.

The transition could happen quickly, he said, adding that some studies suggest that climate change is contributing to more frequent, extreme fluctuations from La Niña to El Niño.

But even when a strong El Niño develops, it doesn’t always translate into the weather that people expect.

In 2015-16, a strong El Niño was predicted — some forecasters are calling it a Godzilla El Niño — but California’s annual rainfall totals ended up being about average, said state meteorologist Michael Anderson.

But in 1982-83, when another excellent El Niño occurred, hurricanes destroyed many piers and removed a 400-foot section of the Santa Monica Pier. The state’s rainfall at the end of the year will be determined by many factors, such as the frequency and strength of atmospheric currents, rather than what will technically be an El Niño year, he said.

In Southern California, strong El Niños increase the likelihood of a wet winter that fills the water table and reduces the risk of wildfires but can also cause flooding, debris flows and coastal erosion. However, the exact results cannot be predicted.

El Niños typically strengthen the subtropical jet stream, meaning much of California’s fall and winter weather tends to come in from the south, as opposed to the north, bringing warm air that carries more moisture, said O’Brien, a US Forest Service meteorologist.

This can help reduce the intensity of Southern California’s wildfires in the fall and winter, which are often shaped by the presence of Santa Ana winds. El Niño is skewing the chances of early winter rain that could ease the danger of those winds fanning the flames, O’Brien said.

“We’re very hopeful that we’ll get rain in the fall that prevents the Santa Ana winds and reduces our chances of going into fall and winter next year,” he said.

However, there is still a lot of uncertainty.

The climate system in the tropical Pacific is naturally less predictable in March and April, and even the most advanced models cannot predict how conditions will evolve, Tim Stockdale, chief scientist at the European Center for Medium-Range Weather Forecasts, wrote in an email. The picture is usually clearest between late May and June, he said.

But it’s not just Earth’s creatures that should be watching for El Niño.

The pattern, which may reduce the nutritional value of plankton, is believed to have exacerbated the effects of unusually warm ocean waters off the California coast that lasted from 2013 to 2016, leading to the deaths of sea lions whose starving mothers could not produce enough milk to sustain them.

The breeding season for sea lions and breeding season is fast approaching in large areas such as the Channel Islands, according to Giancarlo Rulli, associate director of public relations for the Marine Mammal Center. “Experts are looking at current oceanography reports with a healthy level of concern,” he wrote in an email.

Times Deputy Editor Monte Morin contributed to this report.