El Nino arrives in Pacific with high odds of historic winter strength

Scientists at the National Oceanic and Atmospheric Administration (NOAA) announced on Thursday a 63 percent chance that very strong El Nino conditions will form between November and January. This year’s event could rival the strongest occurrences since modern record-keeping began in 1950.

“We’re seeing a pretty clear atmospheric response in the pattern of pressure, winds, and rainfall over the tropical Pacific Ocean,” said Michelle L’Heureux, a meteorologist with NOAA’s forecast team. “Communities should see this as an option to assess risk and prepare.”

El Niño events occur when ocean waters along the South American equator become unusually warm, fundamentally altering global weather patterns. Currently, water temperatures in the region are around 1.3 degrees Fahrenheit above normal. NOAA indicates a high probability that these temperatures will spike to 3.6 degrees Fahrenheit above normal by winter.

While strong El Nino events historically tend to increase the likelihood of above-average winter rainfall in California, especially in southern and coastal areas, results can vary widely.

The powerful El Niño episodes of 1982-83 and 1997-98 caused frequent heavy rains and severe flooding across the state. In contrast, the much-anticipated 2015-16 event led to an average winter in the Bay Area and drier-than-usual conditions in Southern California.

“Strong El Niños mean that we have a high chance of above-normal precipitation but no guarantees,” emphasized Jan Null, a meteorologist with Golden Gate Weather Services.

Beyond California, a very strong El Niño starts to have major global impacts. The phenomenon generally causes wetter conditions across the southern half of the United States, a weaker Atlantic hurricane season, severe droughts in Australia and Indonesia, and extreme heatwaves in India.

Climate scientists fear that while climate change does not cause El Nino, rising global temperatures can worsen its effects, making storms wetter and heatwaves hotter.

NOAA will continue to issue monthly updates as researchers monitor ocean temperatures leading into the winter season.