On Friday, October 6, the first big cold front of fall will push through a lot of the Southeast, bringing much cooler and drier conditions to the region. It will be a fairly dry front, though, so not much relief from the dry conditions we have been experiencing the past few weeks. Since we are currently in an El Niño, people have been asking me how the El Niño will affect our winter weather. Here are a few thoughts, but keep in mind that each El Niño is unique and so there will likely be a surprise or two in what the winter looks like compared to what we predict using analogs of previous events and statistics. A further complication is the presence of unusually warm ocean waters in the Atlantic and Gulf, due at least in part to the world’s trend towards warmer conditions over time from warming due to greenhouse gases. That means to some extent we are in uncharted territory, since the unusually warm water will heat the atmosphere above it, and that will affect the position of high- and low-pressure centers that help drive the winds across the globe. And there are sometimes wild cards like sudden stratospheric warmings that can alter patterns, too.

According to NOAA’s Climate Prediction Center, the chances that this El Niño will be a strong one (≥1.5°C for the November-January seasonal average in Niño-3.4) are 71%. The El Niño is expected to last at least through the January through March period (95% chance) before it swings back to neutral conditions. The set of maps below shows the precipitation patterns that occurred in each of the recent strong or very strong El Niños across the continental United States (maps courtesy of Jan Null). If you compare the patterns, you can see that in most of these years, the Southeast is quite wet compared to average, especially in the southern half of the region. But in 1987-88, in spite of the strong El Niño, there was only a small band of wetter than normal conditions, so while we generally expect wet conditions in an El Niño winter, they don’t always occur. At this point, the best we can say is that it is likely that the coming winter will be wetter than normal in most of the Southeast, but it’s not 100% sure. It does mean that the chances of a drought in spring and early summer are lower than normal because of plenty of soil moisture. In fact, if it’s a very strong El Niño and correspondingly wet, it will likely delay farmers from getting into their fields in spring and could also hold the soil temperature down as sunlight will go into evaporating the moisture rather than warming up the soil. Both of those effects mean a late start to the planting season will be more likely than usual next spring.

Temperatures are a little more difficult to predict because we are feeling a tug-of-war between the El Niño cloudy and cool conditions we expect based on past events and the upward trend in temperature due to global warming. The Climate Prediction Center has put most of the Southeast into “equal chances” of near-, above- and below-normal temperatures, with the highest chances of warm conditions in Florida and along the coasts closest to the warm ocean water (see map on the bottom of the page). The cooler temperatures will be more apparent in daytime high temperatures, which will be depressed due to the cloudy and rainy conditions, than in the overnight low temperatures, which could be warmer because the clouds trap surface heat from escaping from the atmosphere. Could it reduce the chance of frost? Possibly, but because freezes and frosts are weather events that depend on short-term atmospheric conditions rather than statistical relationships, we can’t say for sure. The same thing would be true of the likelihood of snow, since snow forms in the Southeast under very specific weather conditions that occur over just a few days, a much shorter time period than the seasonal climate record.

One thing we do expect, and that is an increase in severe weather over the winter and early spring in Florida and southern Alabama and Georgia, while severe weather in the traditional “Tornado Alley” in Oklahoma and surrounding states is less frequent than in neutral or La Niña winters. Of course, in the Southeast we can and do get severe weather in every month of the year, but this winter you can expect to see it more often than usual.

If you are interested in reading more about how El Niño is likely to affect this winter’s climate, you can check out these links below. A new NOAA update on El Niño should be out in a few days, and you will be able to view it at https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml. The official graphical outlooks for October through December 2023 are below the links.

Climate.gov: ENSO and tornadoes

Kirk Mellish: El Nino’s tale of winter

The Hill: NOAA releases 2023-2024 winter predictions

Weather.com: How An El Niño Could Impact Winter Snow

Accuweather: US winter forecast for the 2023-2024 season