Forecasts Indicate Possible Strong El Niño Event for California This Year

The National Oceanic and Atmospheric Administration (NOAA) released a forecast on Thursday indicating a more than 90% chance of an El Niño developing by fall and a 50% chance it will be at least a strong event. The European Center for Medium-Range Weather Forecasts reported that sea surface temperatures could exceed the seasonal average by 2 degrees Celsius.

NOAA estimates the odds of such warming by late fall at 1 in 4.

El Niño refers to warmer-than-average waters along the equatorial Pacific that influence global weather patterns. It forms part of the El Niño-Southern Oscillation cycle, where changes in tropical trade winds allow warm seawater to shift eastward across the Pacific toward the Americas.

This warm water releases heat into the atmosphere, which can alter jet streams and direct storms toward Southern California and the southern United States.

The amount of warm water available for this year's event exceeds that during the 1997-98 El Niño, which was among the strongest of the century, according to Paul Roundy, professor of atmospheric science at the University of Albany. That event brought a series of storms to California, causing flooding, debris flows, destruction of homes and roads, and 17 deaths.

Globally, it contributed to a deadly hurricane in Acapulco and severe drought in Indonesia.

predicts a roughly 20% chance that this year's El Niño could be stronger than any since the late 1870s, when droughts in India, China, and Israel resulted in an estimated 30 million to 40 million deaths.

Some experts classify El Niño events with sea surface temperatures exceeding the seasonal average by 2 degrees Celsius as "super" El Niño, which are rarer and associated with broader effects. U.S. Forest Service, described such events as the upper echelon of El Niño occurrences.

In Southern California, strong El Niño events increase the likelihood of wet winters that replenish water supplies and reduce wildfire risk. However, they can also cause flooding, debris flows, and coastal erosion. The 1982-83 super El Niño, for example, destroyed multiple piers and removed a 400-foot section of the Santa Monica Pier.

The 2015-16 El Niño was forecasted as a super event, but California's rainfall totals were about average, according to state climatologist Michael Anderson.

Rainfall outcomes depend on factors such as the frequency and strength of atmospheric rivers, beyond the El Niño designation alone. Nathaniel Johnson, a meteorologist at NOAA's Geophysical Fluid Dynamics Lab, noted that the transition to El Niño could occur rapidly, with some research suggesting climate change contributes to more frequent extreme swings between El Niño and La Niña phases.

Stakeholders in California, including water managers, emergency responders, and coastal communities, monitor these forecasts to prepare for potential impacts.

Water agencies may adjust reservoir operations to capture increased rainfall, while fire agencies could see reduced immediate risks but heightened flood concerns. Next steps include ongoing monitoring by NOAA and other agencies through the fall to refine predictions as the event develops.