The El Niño-Southern Oscillation, also known as ENSO, is a phenomenon that occurs in the tropical Pacific Ocean. When average water temperatures are above average, it dictates that an El Niño is present; when temperatures are below average, La Niña is present. These phenomena not only bring cooler or warmer-than-average temperatures but also create shifts in the wind shear around the globe and changes in the position of the jet stream, which bring significant changes in weather patterns while they are present. La Niña events typically occur every 3 to 5 years, but the interval between events can vary from 2 to 7 years.
El Niño or La Niña may be present at any time of the year, but depending on the season, some regions may be more severely affected by even worse extreme weather conditions. This fall, La Niña appears to be slowly developing. Scientists said that there is a 71 percent chance of La Niña developing and persisting through December. However, between December and February, during the winter months, there is a 54 percent chance of this happening, and long-term models continue to indicate a decrease through the spring of 2026. This shift in the pattern is expected to last at least through February 2025.
How does La Niña affect the fall andwinter?
When La Niña is present in the cooler months, it typically displaces the jet stream, causing it to shift more northward; this tends to bring drier and warmer-than-normal conditions during its duration. The jet stream´s northward displacement keeps storms moving across northern latitudes and less frequent, more south. Fewer storms moving across the South means the weather pattern will stay drier, and with fewer storms that bring clouds, temperatures tend to stay warmer. Water temperatures also tend to stay warmer than average across the Gulf and eastern Atlantic.
La Niña: What Does It Mean for South Carolina?
When a La Niña is present in winter, the season tends to stay warmer and drier than usual. This pattern was present during the winter of 2016-2017. These months, temperatures have remained warmer than average. Winters across South Carolina, on average, are mild, with temperatures ranging from the mid-30s in the mountains to the low 50s in the Midlands.
Having a La Niña event does not mean we will not experience cold snaps. There will be storms and some cold fronts, but they will be less frequent and perhaps less intense. Once the season is over, we will look back and notice that the overall trend was warmer than average.