If you pay attention to long-range weather forecasts, you'll often hear words like "El Niño" or "La Niña." While it's common language to us, it might not be to you.

Days ago, the National Oceanic and Atmospheric Administration (NOAA) put a 71% chance of La Niña conditions from October to December and a 54% chance of it in December to February.

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Odds of La Niña developing October through February (NOAA)
Odds of La Niña developing October through February (NOAA) (© WRAL)

What is La Niña?

This is all part of the El Niño Southern Oscillation - ENSO. (We love acronyms in meteorology.) The ENSO refers to different trends in ocean temperatures (generally) off the coast of Peru.

A La Niña refers to cooler-than-average waters in the eastern equatorial Pacific Ocean.

La Niña refers to cooler-than-average ocean waters in the eastern equatorial Pacific Ocean
La Niña refers to cooler-than-average ocean waters in the eastern equatorial Pacific Ocean (© WRAL)

So you might be asking...

Why do we care about La Niña if it's in the Pacific?

Oceanography and meteorology have some connections. The ENSO is one of them.

A cooler-than-average region of the Pacific can alter the upper level winds that drive our weather.

For instance, a La Niña will usually lead to a more active jet stream in the western and central U.S.

What goes down must come up, meaning that the jet stream usually stays locked north of the Eastern U.S.

How La Niña typically effects the jet stream over the U.S.
How La Niña typically effects the jet stream over the U.S. (© WRAL)

What does this mean in the fall and winter months?

It's not to say that you'd never see dips in the jet stream (ie. cold fronts, precipitation, etc.). However, they'd become less frequent in an idealized La Niña situation.

You could infer three things.

Theoretical impacts of La Niña in North Carolina
Theoretical impacts of La Niña in North Carolina (© WRAL)
  1. Weaker upper level winds could favor late season tropical development in the Gulf and in the Caribbean. Remember that hurricane season runs through November 30.
    1. The lack of upper level disturbances could mean drought in parts of the Eastern U.S. This would imply the potential for wildfires. NOAA's Climate Prediction Center shows this being possible along Virginia's Blue Ridge and the Shenandoah Valley.
      1. In the winter, this tends to lead to less activity in the Eastern U.S. In Raleigh, 64% of La Niña winters yield below-average snowfall.

        These are trends we'll watch for in the coming weeks. When it comes to a winter forecast, there are several other factors to take into account. And long-range forecasting lacks the skill of a day-to-day forecast.

        Have questions about the weather and how it works?

        Send me an email with the subject line 'Ask the Meteorologist:' to cmichaels@pugongyingbo.com.