El Niño Forecast: Probabilities Rise, Potential for "Very Strong" Event
The Climate Prediction Center (CPC) has increased the probability of El Niño emerging in the coming months to 82%, with a 96% chance it will be in force this winter.
Forecasts from the National Oceanic and Atmospheric Administration (NOAA) indicate a 63% probability that this El Niño could be "very strong" by the end of the year. While historical data shows that very strong El Niños have been associated with higher-than-average precipitation in Southern California, the relationship is not consistent, as demonstrated by the 2015-16 event which did not produce heavy rainfall.
El Niño Forecast and Strength Probabilities
- The CPC has raised the probability of El Niño emergence to 82%, up from 61% a month ago.
- The chance that El Niño will be in force this winter is 96%.
- Probabilities for El Niño strength by year-end are: 37% very strong, 30% strong, 22% moderate, and 9% weak.
- NOAA reports a 63% chance El Niño could be "very strong" toward the end of the year, and an 88% chance of being either "very strong" or "strong."
- Previous very strong El Niños occurred in 1982-83, 1997-98, and 2015-16. The 1991-92 El Niño has been recategorized as very strong.
Potential Impacts on Winter Precipitation
- El Niño is typically associated with higher-than-average precipitation in Southern California, according to the National Weather Service.
- A strong El Niño can shift the subtropical jet stream, directing storms toward California and the southern United States.
- Two of the last four "very strong" El Niños (1982-83, 1997-98) delivered over 30 inches of rain to downtown Los Angeles, more than double the annual average. The 1991-92 event brought 20.86 inches (150% of average).
- The 2023-24 moderate El Niño coincided with 155% of typical annual rainfall in downtown L.A., leading to record precipitation and hundreds of mudslides in February.
- According to NOAA, stormier weather is generally more likely in the southern U.S. during El Niño, while the Pacific Northwest tends to be drier.
- UC climate scientist Daniel Swain noted that a very strong El Niño could increase odds of unusually wet conditions and heavy precipitation events, possibly raising flood risk.
- The relationship between El Niño and Southern California winter wetness has been less reliable since 2000. The 2015-16 very strong event resulted in only 6.88 inches of rain (about half the annual average) but caused record coastal erosion.
- El Niño does not guarantee extreme rainfall in Southern California; other factors, such as atmospheric rivers, also influence precipitation.
- A wet winter could provide relief to the Colorado River basin, which is currently in an "exceptionally severe multi-decadal drought."
Coastal and Ecosystem Effects
- NOAA states that elevated sea levels along the West Coast can cause high tides and surf to ride higher and push further inland.
- Swain noted that major El Niños can raise local sea level by 6–10 inches in California during winter, increasing coastal flooding risk.
- The 2015-16 El Niño brought "record coastal erosion along many California beaches," per the California Coastal Commission.
- The current marine heat wave off the West Coast may be prolonged by El Niño, potentially disrupting marine ecosystems.
- Warmer ocean temperatures may increase sightings of tropical or subtropical species, including sharks and Portuguese man o' war.
- Nate Jaros (Aquarium of the Pacific) said warmer waters may attract tropical species, including increased shark sightings and, rarely, whale sharks (as seen in 2015-16).
- Andrew Leising (NOAA Southwest Fisheries Science Center) noted marine mammals and migratory species may move closer to shore following food sources.
- Past marine heat waves have caused a 90% decline of bull kelp habitats in Northern California since 2014, affecting species like white abalone and sunflower sea star.
- Strong El Niños have been associated with decreased plankton, increased harmful algal blooms, lower abundance and northward shift of market squid, reduced productivity of California sea lions, and smaller pups.
- The combination of the 2014-16 marine heat wave ("The Blob") and strong El Niño led to closures of crab and shellfish fisheries, increased whale entanglements, loss of groundfish habitat, and die-offs of seals, sea lions, and marine birds.
Current Storm Conditions and Preparedness
As of early January 2025, California is experiencing a significantly wet winter. A powerful storm system is forecast to move into the state, bringing heavy rain, snow, and strong winds.
Recorded Rainfall- The Los Angeles region has recorded above-average precipitation since the current rainy season commenced on October 1.
- Multiple daily rainfall records were surpassed during a recent storm affecting the Rose Parade:
- Oxnard: 1.09 inches
- Sanberg: 1.25 inches
- Hollywood Burbank Airport: 1.32 inches
- Long Beach Airport: 1.11 inches
- Lancaster: 0.87 inches
- Downtown Los Angeles has received 11.64 inches of rain, approximately 82% of its normal rainfall for the entire water year.
- Sanberg has recorded its wettest start to the water year since 1934, with over 16 inches of rain through Wednesday, exceeding its typical annual average of 13.14 inches.
A storm system is forecast to arrive on Sunday, with the most intense period projected from late Sunday through Monday.
- Coastal and valley areas in Southern California are expected to receive 1 to 3 inches of rain, with foothills and mountains receiving 3 to 6 inches.
- Rainfall rates are estimated between 0.25 to 0.5 inch per hour, with localized rates potentially reaching 1 inch per hour.
- Snow levels are expected to remain above 6,000 feet for most of the storm's duration, with 2 to 6 inches of snow above 7,500 feet.
- A high-surf advisory is likely for Southern California beaches from Monday to Thursday, with wave sets exceeding 10 feet possible.
- California's Office of Emergency Services has positioned fire and rescue personnel and resources in areas prone to flooding, mud, and debris flows.
- Evacuation warnings have been issued for burn scar areas of the Palisades and Eaton fires in Los Angeles County.
- The Los Angeles County Department of Public Health has advised the public to avoid ocean water at beaches due to elevated bacteria levels.
- Wind advisories have been issued for higher-elevation areas of Ventura and Santa Barbara county mountains.
- Winter storm warnings are active from southwest Oregon to the Southern California border.
- PG&E stated it was utilizing artificial intelligence and machine-learning weather models to direct crews and equipment.
Broader Climate and Weather Whiplash Context
UC climate scientist Daniel Swain stated that recent extreme weather events in Southern California, including heat, dryness, wetness, and severe wildfires, are clearly linked to climate change.
He noted that a warmer atmosphere extracts more moisture from soils and plants, worsening droughts, while also holding more water vapor, resulting in fewer but more extreme rainstorms. The rapid shift from intense rain to extreme heat is consistent with scientific expectations for Southern California as climate change intensifies.
Heavy rainfall promotes the growth of grass and brush, which then becomes abundant fuel during dry periods. This sequence was observed before the Palisades and Eaton fires, following very wet winters in 2022 and 2023 and a dry period in late 2024.
Long-term Outlook
Following the current storm cycle, a period of dry weather, potentially lasting up to two weeks, is projected. El Niño could bring tropical storm remnants to Southern California in late summer, potentially preventing a severe fire season, or alternatively, lead to dry-thunderstorm outbreaks and lightning-induced wildfires.
California's water infrastructure currently has significant water levels in state reservoirs from the recent wet winter. Swain remarked that a multi-year drought of significant severity would be required to threaten water supply, though prolonged dryness can still affect California's agricultural sector and increase wildfire risk.