A periodic warming of the tropical Pacific Ocean, known as El Niño, has reached a "very strong" or "super" category, according to UC Irvine atmosphere and climate expert Jin-Yi Yu. While this phenomenon often causes above-average rainfall in the U.S. Southwest during winter and spring, its specific impact on Southern California's upcoming rainy season remains uncertain.
The National Oceanic and Atmospheric Administration (NOAA) reported on September 21 that the sea surface temperature in a central Pacific Ocean region was 3.11 degrees Celsius above average, surpassing a previous record of 3.08 degrees. A NOAA computer model predicts this water temperature could peak near 4 degrees Celsius above average in November. Professor Yu, from UC Irvine’s Earth system science department, notes that the El Niño Southern Oscillation research community generally anticipates this to become one of the strongest, "and possibly the strongest," El Niños in the modern observational record.
Despite the intensity, a stronger El Niño does not guarantee a wet winter for Southern California. Yu points to the 2015-16 super El Niño, which was also widely expected to bring heavy rainfall but ultimately did not materialize. He advises caution against assuming an exceptionally wet winter, even if this El Niño becomes the strongest on record.
Scientists are finding it challenging to use El Niño as a direct predictor for heavy winter rain in California due to additional global warming factors. Yu's team is tracking a warm water mass along the equator in the central Pacific Ocean and a "blob" of abnormally high-temperature seawater in the Gulf of Alaska. These additional masses of heated water complicate the traditional El Niño pattern. Yu's research identifies four factors contributing to the central Pacific El Niño: global warming, deforestation in Southeast Asia, a 60-to-80-year warming and cooling trend in the Atlantic Ocean affecting Pacific air circulation, and an active 11-year solar cycle influencing El Niño frequency and severity. The critical question remains whether the jet stream will be pushed south as in past events, which would bring significant winter rain to Southern California.
While the rainfall outlook is complex, coastal areas may see more immediate effects. Brett Sanders, Chancellor’s Professor of civil and environmental engineering at UC Irvine, predicts that El Niño will bring "another round of high wave energy in winter, most likely between December and February, along with the highest tides we’ve had in years." He suggests a high probability of record-setting tides that could lead to significant flooding in low-lying coastal areas. Seasonal forecast models also indicate an increased chance of a wet winter with heavy rainfall. Flood control districts across California are preparing by cleaning reservoirs, debris basins, and flood channels, though Sanders cautions that protection is not absolute and system overtopping is always a possibility during extreme weather.
Beyond preparing for property damage, UC Irvine experts emphasize public health readiness. Bernadette Boden-Albala, founding dean of the Joe C. Wen School of Population & Public Health, states that "Disaster preparedness is public health preparedness." She advises residents to consider health needs that may become urgent when routines are disrupted, beyond just water, flashlights, and batteries.
Karen Lincoln, director of UC Irvine’s Center for Environmental Health Disparities Research, highlights the unique challenges faced by people living with dementia and their caregivers during emergencies. She notes a lack of specific preparedness guidelines or training for this group. Lincoln suggests preparing by considering how to reduce confusion, anxiety, and distress when familiar routines are disrupted. This includes having familiar comfort items, a simple activity, a written reminder of daily routines, and information about what helps calm an individual, making an emergency less overwhelming for them.
