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How La Niña Affects US Winter Weather: NPR

This Climate.gov graphic shows how La Niña generally affects weather conditions in the United States. Forecasters say the La Niña condition is almost 90% likely to occur between December 2021 and February 2022.

National Oceanic and Atmospheric Administration


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National Oceanic and Atmospheric Administration

This Climate.gov graphic shows how La Niña generally affects weather conditions in the United States. Forecasters say the La Niña condition is almost 90% likely to occur between December 2021 and February 2022.

National Oceanic and Atmospheric Administration

According to federal forecasts, La Niña is likely to rejoin in the winter.

National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center Announced on Thursday The La Niña phenomenon has occurred and is expected to continue, with an 87% chance of occurring from December to February.

La Niña (translated from Spanish as “little girl”) is not a storm, but it is a climate pattern that occurs every few years in the Pacific Ocean and can affect the weather around the world.

The United States is expected to feel impacts on temperature and precipitation, which can affect hurricanes, tornadoes, droughts, and more.

Forecasters point out that this is actually the second La Niña winter and not a rare phenomenon they call. “Double dip”. The latest period lasted from August 2020 to April 2021. (We’ll talk more about what happened after that.)

“Our scientists have been tracking the potential development of the La Niña phenomenon since this summer, which is more than normal during the hurricane season,” said Mike Harpert, deputy director of the NOAA’s Center for Climate Prediction. Was a factor in the forecast. ” At release. “La Niña also affects the national weather during the winter, which affects our outlook for future temperatures and precipitation.”

NOAA will release it Official winter outlook In the meantime, there is an introductory book on how La Niña works and what it means for different parts of the country.

What exactly is La Niña?

Scientists emphasize that La Niña is not a storm that hits a particular area at a particular time. Instead, it is a change in the Earth’s atmospheric circulation that affects the weather around the world.

“Think about how large-scale construction projects throughout the town can change the flow of traffic near homes, such as rerouting people, increasing side road traffic, and closing regular exits and ramps. Please try. ” NOAA writes.. “Different areas are most affected by different times of the day. You will feel the effects of a construction project through changes to the normal pattern, but you don’t think the construction project will” hit “your home. Probably. ”

Let’s start with a technical explanation. It is part of the El Nino Southern Oscillation Cycle (ENSO), a natural climatic pattern defined by countering the warm and cold stages of the Pacific ocean and atmospheric conditions.

The La Niña and the corresponding El Nino phenomenon alternately cool and warm large areas of the tropical sea about every two to seven years on average. (There is also a “neutral” state, which is the state since the last La Niña was finished.)

As the agency explains (With useful flowchart), Forecasters can officially declare the La Niña phenomenon When sea surface temperature falls below a certain level, it remains below that threshold and is modeled to drive significant atmospheric responses such as wind changes.

This is how it works.

“Under normal conditions in the Pacific Ocean, trade winds blow west along the equator, carrying warm water from South America to Asia. To replace that warm water, cold water rises from the depths. Is a process called uplift. ” NOAA explains.. “El Nino and La Niña are two conflicting climate patterns that break these normal conditions.”

Under La Niña conditions, trade winds are stronger than normal, pushing warmer water into Asia. On the other hand, off the west coast of the Americas, increased upwelling sends cold water toward the surface. (Nutrition-rich water also attracts more cold-water species such as squid and salmon to places like the California coast.)

Cold water moves the jet stream north and then weakens in the eastern Pacific Ocean.

So how does it actually feel on the ground?

According to NOAA, La Niña’s greatest impact on North American rain, snow and temperature tends to be felt during the winter months.

Generally speaking, winters in La Niña tend to be drier and warmer than usual in the southern United States, and cooler and rainier in the northern United States and Canada.

The Pacific Northwest, parts of the Midwest, and valleys of Tennessee and Ohio have more rain and snow than normal winters.

La Niña can also lead to a tougher Atlantic hurricane season. We are already watching This year.

The main thing the forecasters emphasize is that the La Niña phenomenon is associated with specific climate patterns, namely deviations in temperature and rainfall in different parts of the country, but they are a problem. “Probability, not certainty.“”

So if you’re wondering if La Niña will affect your home this winter, NOAA scientist Provides this answer:

“Maybe. Maybe. Maybe not. The answer depends on many factors, including where you live, how strong the event is, and other climatic patterns that affect seasonal outcomes.”

What about meteorological events such as snow, floods and tornadoes?

Snow is hard to predict, However, experts say La Niña has the potential to increase snowfall in the northwestern, northern Rocky Mountains, and upper Midwestern Great Lakes regions. The southwestern, mid-southern plains, and parts of the Mid-Atlantic coast may appear less than normal.

La Niña generally contributes to the increase in Atlantic hurricane, but less in the East and Central Pacific (as opposed to El Nino). As NOAA explains, these Atlantic hurricanes form in the deep tropics from the waves of eastern Africa, making them more likely to be the major hurricanes that can hit the Caribbean and the United States.

The location of the jet stream also seems to affect the tornado, giving you an idea of ​​where in the country the tornado is likely to occur.Jet stream and stormy weather during the La Niña winter It may be further north.

La Niña can also exacerbate the ongoing drought in California, further threatening the wildfire season. NS Bloomberg explains, The state usually gets most of the water every year from rain and snow between November and April — at the same time that La Niña is predicted to shift the stormy road north. And away from the areas that need it.

Droughts can be prolonged in the southern United States, but heavy rains and floods can occur in the northern part of the country, especially in the Pacific Northwest.

How long does it last, and how often does it happen?

NS State Oceanic Administration El Nino and La Niña episodes usually last 9-12 months, but in some cases can last for years.

Both of them tend to develop in spring, reach peak intensity in late autumn or winter, and then weaken in spring or summer.

In other words, La Niña will have the strongest impact on the United States. Between January and MarchHowever, it may remain in early spring.

Why is it called it?

NS The inside story goesSouth American fishermen have long observed warmer than usual Pacific coastal waters and dramatic reductions in catches occurring around Christmas. They called the phenomenon “El Nino” (Spanish for “little boy”) and named it after the baby Jesus.

So when scientists discovered the opposite stage of El Nino in the 1980s, they decided to call it “La Niña”. (Of course, the language about Gender identity and expression There are more subtle nuances these days. )

How does this relate to climate change?

It’s too early for scientists to say exactly how a warmer world affects the ENSO cycle.

“But don’t forget that just because you’re not very confident about how ENSO will change in the future doesn’t mean it won’t change,” NOAA wrote. 2016 blog post.. “It just means that scientists have more to do.”

However, I am confident that ENSO itself will continue. And they say global warming is likely to affect the effects of La Niña, including extreme weather events.

How La Niña Affects US Winter Weather: NPR

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