NASHVILLE, Tenn. (WKRN) — The Climate Prediction Center has issued a La Niña Watch! So, what is a La Niña Watch, and why does it matter?

News 2 spoke with climate expert meteorologist Nat Johnson, and he said a La Niña Watch is what the Climate Prediction Center issues when they expect a La Niña over the next few months.

Johnson said La Niña is the cold phase of the El Niño Southern Oscillation. He said a La Niña occurs when the sea surface temperatures are cooler than normal in the eastern equatorial Pacific Ocean.

La Niña is just the opposite of El Niño. El Niño is when the temperatures in the same location are warmer than normal.

Johnson said scientists focus on it because it is one of the best tools for making seasonal forecasts, especially forecasts for the winter.

"Among all the phenomena that can impact our weather over an entire season, ENSO is the most predictable," Johnson told News 2. "There are many other factors that can shape our weather during a season, but many of them are not predictable beyond a couple of weeks."

He said El Niño and La Niña have very different impacts on the winter weather in the United States.

According to Johnson, the forecast is for another weak La Niña. This is exactly what we experienced last winter.

Johnson told News 2 that we could have a similar winter to last year, but it is unlikely because there are other factors that impact the weather during our winters.

"Sometimes, the weather we experience looks nothing like the impacts of El Niño or La Niña, because other factors dominate. So I would not expect this winter to be a mirror or repeat of what we saw last year," Johnson explained.

Last year, Nashville saw a snowier-than-normal winter with over 9" of snowfall, temperatures near normal and slightly above average rainfall.

News Source : https://www.wkrn.com/weather-headlines/la-nina-watch-explainer/