La Niña is expected this winter; here’s what that means for us

MONTGOMERY, Ala. (WSFA) - It’s back again! La Niña conditions have officially developed and are expected to remain in place through the entirety of winter 2021-2022. So what exactly does that mean?

La Niña means we’re in the negative phase of the El Niño Southern Oscillation, or ENSO for short. Per NOAA, La Niña is defined as cooler than normal sea-surface temperatures in the central and eastern tropical Pacific Ocean that impact global weather patterns.

These cooler sea-surface temperatures occur because the negative phase of ENSO results in faster trade winds over the central Pacific Ocean. Those faster winds cool the water, which can lead to La Niña conditions.

When these cooler sea-surface temperatures set up and persist, the weather patterns across the United States can be affected -- at least to an extent. To get a better idea of how a La Niña may impact our weather, we can look at just how “strong” the La Niña is forecast to be.

A La Niña can be weak, moderate or strong. This winter, at its peak intensity, La Niña is projected to be moderate in strength.

That results in a pattern supportive of warmer-than-normal and drier-than-normal conditions here in Alabama during the winter months. When talking winter, we use meteorological winter, which is December, January and February.

There is an 87% chance that La Niña persists during the the December 2021 to February 2022 stretch. That is about as high as it gets when looking at future probabilities of a La Niña.

Thus, it’s fair to say we have a pretty good chance of seeing a warmer and drier winter than what we would typically see. That will be especially true if we see the strength of La Niña reach the moderate category.

Of course, this is the opposite of what an El Niño winter brings to Alabama and the rest of the Southeast. El Niño winters are usually wetter-than-average and cooler-than-average.

It’s important to remember that the ENSO phase we’re in -- El Niño, La Niña or neutral -- doesn’t provide an exact forecast for winter. It gives us a more general idea of what to expect. Just because December, January and February are more likely to be warmer and drier than a normal winter doesn’t mean we won’t have bouts of cooler or wetter weather.

For example, last winter we were in the La Niña phase of ENSO, but we had some very chilly days and very cold nights mixed in. Montgomery had a low of 19 degrees in February and had plenty of additional nights down in the 20s. Those temperatures are certainly below normal for Central Alabama.

So yes, I’d look for a winter that is relatively mild, dry and quiet overall. However, I’d use caution in assuming that we won’t have any cold or even snowy days. The chances are we’ll likely have at least a few days that are rather cold. We also can’t rule out an instance or two of snow -- similar to last year’s flurries.

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