Winter is coming.

No really, the weather phenomenon known as La Niña — the opposite of its more well-known sibling, El Niño — has arrived, the National Weather Service reported Thursday.

Typically, this means cold and snowy conditions in the Pacific Northwest and drier weather in southern parts of the U.S., like Southern California and the Carolinas, between late fall and early spring.

But what exactly is La Niña and why should we be paying attention to it? Here are a few things to know about this weather phenomenon and what Californians should expect in the coming months:

What is La Niña?

The National Oceanic and Atmospheric Administration defines La Niña (Spanish for “little girl”) as a natural ocean-atmospheric phenomenon distinguished by its cooler-than-average sea surface temperatures along the equator in the Pacific Ocean, just off the coast of South America.

Here is a really useful graphic that helps illustrate the weather pattern.

How is it different from El Niño?

La Nina is the opposite of El Niño (Spanish for “little boy”) — they’re both part of a seesawing weather pattern known as El Niño-Southern Oscillation (ENSO), which is a term that scientists use to describe fluctuations in temperature that swing back and forth along the equator in the Pacific Ocean.

El Niño can be thought of as the warm phase of the ENSO pattern, and La Niña is the colder phase of the pattern, according to NOAA.

What kind of weather should California expect?

Meteorologists in California have begun to ring the bells for what’s to be expected during the winter, some saying that it will be a weaker-than-usual La Niña. Forecasters say to expect a weak weather event in the early months of 2018, meaning Northern California can expect cooler, wetter conditions while Southern California will experience warmer, drier weather patterns.

Here’s what that will look like Southern California per a poem from the National Weather Service.

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Email: luis.gomez@sduniontribune.com

Twitter: @RunGomez

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