by Julia Pierrepont III
LOS ANGELES, April 9 (Xinhua) -- New reports on seasonal outlooks from the U.S. National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center and the European Centre for Medium-Range Weather Forecasts have spotted an important warming signal that, if it strengthens, could have powerful repercussions on Southern California and worldwide.
Forecasters say ocean heat building along the equator today could set the stage for an unusually strong El Nino later this year, a climate pattern that U.S. agency says could tilt the odds toward wetter, stormier weather in Southern California and other parts of the West, and send ripple effects that could impact the Atlantic Ocean hurricane season and weather systems as far-flung as Southeast Asia.
The agency defines El Nino and La Nina as opposite phases of the El Nino-Southern Oscillation, or ENSO, and El Nino tends to shift the winter storm track south, raising the chances of wetter-than-normal conditions in Southern California, while La Nina often nudges storms north, increasing the odds of drier stretches.
For Southern Californians, the biggest concern is not one rainy day but repeated high-intensity storms that El Nino can bring, which can overwhelm drainage systems and oversaturate arid slopes. The California Coastal Commission warns that wildfire burn scars and dry, steep terrain can collapse quickly, sending mud, rocks and vegetation tumbling downhill onto unsuspecting communities below, while deep offshore storms can drive dangerous surf and cause beach and cliff erosion.
In past El Nino events, rain has alternated between soaking storms and long dry breaks, a swing that can also complicate wildfire planning depending on timing.
When El Nino pushes into the strongest category, "it's essentially the upper echelon of El Nino events," Jonathan O'Brien, a meteorologist with the U.S. Forest Service, told the Los Angeles Times.
What that means for Southern California, according to the National Aeronautics and Space Administration (NASA), is that strong El Nino events raise sea levels and increase extreme precipitation, leading to coastal flooding and inland flood risks along California's coast.
The California Geological Survey also warns that El Nino winters can result in above normal precipitation in Southern California, leading to increased mudslides, road-blocking landslides and catastrophic debris flow activity, following heavy El Nino rainfall.
Even the chance of a powerful event is drawing concern from residents, emergency managers and water agencies.
"I used to have a house on the beach in Malibu," filmmaker "Skippy" Bakel told Xinhua. "I'm glad I'm not living there now."
For California water managers, a strong El Nino is both an opportunity and a risk. The National Weather Service explains how heavy precipitation can boost reservoirs and snowpack, but warmer storms can lift snow levels and turn what might have been stored water into wasted runoff, raising flood concerns while reducing the natural "snowpack reservoir" that slowly releases water in spring and summer.
UCLA climate scientist Daniel Swain has warned against assuming every El Nino looks the same, even when ocean temperatures are unusually warm.
A strong event "does have the potential for strong impacts on California," Swain said, while emphasizing that outcomes still depend on how storms line up over months.
Beyond California, the World Meteorological Organization (WMO) says El Nino significantly impacts weather systems around the globe when warmer Pacific waters release heat into the atmosphere, shifting jet streams and storm tracks, altering atmospheric circulation over the western Pacific, weakening the Walker Circulation and shifting patterns of convection in ways that can influence East and Southeast Asian monsoon systems.
It further reports that strong El Nino events add heat to the atmosphere by releasing stored ocean heat on top of human-caused greenhouse gas warming, an assertion supported by a study published in Nature Climate Change, which projected that extreme El Nino events could become more frequent with greenhouse warming.
This would increase the risk of record global temperatures that drain global power grids and cause related public health issues, while the NOAA Coral Reef Watch explicitly links El Nino-driven ocean heat to marine heatwaves and mass coral bleaching, which disrupt marine ecosystems and fisheries.
With months to go before winter, for safety's sake, public officials are urging Southern California to brace for stormy weather by reviewing evacuation plans for areas below recent burn scars, keeping sandbags and emergency supplies ready, and clearing drains.
Forecasters will continue to track Pacific temperatures and winds for signs El Nino is strengthening, and whether it will reach the rare "super" territory that can seriously amplify extremes. ■
