NOAA Says El Niño Could Reach Historic Strength—What That Means for Fall and Winter
An already strong El Niño continues to intensify across the tropical Pacific, and forecasters say it could become the most powerful event on record since 1950.
You may also hear it called a “super El Niño.” That, however, is not an official scientific category. The World Meteorological Organization (WMO) classifies events as weak, moderate, strong, or very strong and does not use “super El Niño” in its official system.
The National Oceanic and Atmospheric Administration’s (NOAA) Climate Prediction Center (CPC) says there is now more than a 90% chance of a very strong El Niño this fall and winter. The World Meteorological Organization (WMO) likewise describes the event as strong and continuing to intensify, with forecasts showing it could reach the “very strong” category before peaking near the end of the year.
So what is actually happening in the Pacific, and how can warm ocean water thousands of miles away end up influencing the weather outside your window?
How El Niño Works
Typically, winds along the tropical Pacific push warm surface water west toward Asia. As that happens, colder water rises from deeper in the ocean near South America to replace it, a process called upwelling.
During El Niño, however, those trade winds weaken. Warm surface water shifts eastward across the Pacific. Meanwhile, the usual supply of colder water rising up from around South America is reduced, as NOAA’s National Ocean Service explains.
While that change heats the ocean, the domino effect extends far beyond the seas. Warm water helps determine exactly where air rises, how clouds develop, and where rain falls. Since that enormous area of warm water has moved east, tropical thunderstorms shift, and we see changes in atmospheric circulation at a grand scale.
The ripple effect isn’t done just yet.
Eventually, those changes can alter the jet streams that guide storms across North America. NOAA describes it as a chain reaction beginning in the tropical Pacific that ultimately changes the paths taken by weather systems thousands of miles away.
Why This El Niño is Getting So Much Attention
NOAA is now tracking El Niño with a measurement called the Relative Oceanic Niño Index, or RONI. Unlike the older index, RONI compares temperatures in the key El Niño region with temperatures across the wider tropics, as outlined by NWS’s CPC. This methodology helps scientists account for the broader warming of tropical oceans.
Using its current method for measuring El Niño strength, NOAA says there is a 75% chance this event will reach a level not seen in records dating back to 1950 during October through December.
A powerful El Niño does not mean every part of the country will experience its typical effects. Rather, it makes those broader weather patterns more likely as the season proceeds.
So, What Can This Mean For This Fall And Winter
For October through December, NOAA’s latest seasonal outlook anticipates wetter-than-normal conditions across much of the southern and central U.S., including parts of the Southeast, the Mississippi and Tennessee valleys, the Great Plains, the Four Corners, and Southern California.
As winter progresses, NOAA anticipates much of the southern and central United States will continue seeing higher odds of above-normal precipitation. Those chances extend farther north along the Atlantic Coast. Coastal California could also be more likely than usual to have a wetter winter.
At the same time, NOAA expects the northern United States and parts of the West to experience warmer-than-normal temperatures.
El Niño can also influence hurricane season in the Atlantic. According to NOAA’s Atlantic Oceanographic and Meteorological Laboratory, it typically brings stronger wind shear—a sudden change in wind speed or direction—across the Atlantic, Caribbean Sea, and Gulf of Mexico. Those shifting winds, in turn, can disrupt developing storms and, as a result, make it more difficult for hurricanes to form and intensify.
These predictions do not definitively say whether a particular town anywhere will see unprecedented snowfall, endure flooding, or make it through winter without any precipitation. However, El Niño does impact the odds and the pathways available to storms, which is a power in its own right worth knowing about as winter approaches.
With the Pacific continuing to warm and the event expected to strengthen through the end of the year, those odds are shifting more dramatically than they do during an ordinary winter without El Niño—especially in “super” weather systems like these.
