El Niño Has Developed And Will Intensify Through Winter

El Niño conditions have developed, and that could influence hurricane season and the upcoming winter, according to a just-released outlook.

NOAA's Climate Prediction Center (CPC) issued an El Niño advisory in the regularly scheduled monthly update released Thursday.

This means El Niño conditions have been observed and are expected to persist. The advisory is kind of like any other advisory or warning, but for a much longer time period.

What is El Niño? A​n El Niño is a periodic warming of a strip of water straddling the equator in the Pacific Ocean. NOAA declares an El Niño has developed when sea-surface temperatures in a certain region of the equatorial Pacific Ocean have reached at least 0.5 degrees Celsius (0.9 degrees Fahrenheit) above average for at least a month and are accompanied by changes in the atmosphere. That warming is occurring both at the surface and a few hundred meters below the surface, supporting the developing El Niño.

When was the last El Niño? This is the first El Niño in four years. This strip of water has actually been cooler than average over much of the past three years which is known as a La Niña. But that ended by March, and water temperatures in this area have now warmed above the El Niño criteria.

How long will it last? It's expected to last through winter. T​he CPC expects this El Niño will last not just through the peak of the hurricane season but also into at least the first three months of 2024. This is typical for both El Niños and La Niñas. They usually peak in late fall or winter before diminishing the following spring.

This El Niño could be a strong one. Weekly sea-surface temperature anomalies at the end of May were roughly on par with those at the end of May prior to strong El Niños in both 1997 and 1982.

A​ number of computer models continued to forecast either a moderate (at least 1 degree Celsius anomaly) or strong (at least 1.5 degree Celsius anomaly).

P​otential Impacts

The circulation of the atmosphere is affected when this strip of ocean water is either persistently cooler or warmer over several months.

And that was the final criterion needed to declare El Niño conditions.

In an El Niño, the typical trade winds near the equator weaken, leading to less rain near Indonesia and more rain over the central or eastern equatorial Pacific Ocean.

While not the only influence, an El Niño can eventually steer weather patterns in parts of the world, including the tropics and the U.S. The stronger it is, the more influence it could have. Here are some possible impacts.

Summer

Both El Niño and La Niña usually have the most impact on winter weather when they've been in place for several months. B​ut if El Niño intensifies fast enough, it could at least subtly affect both temperatures and rainfall in the U.S. this summer.

A​ccording to an outlook from The Weather Company, an IBM Business, and Atmospheric G2, this summer could be less hot in parts of the East and wet in the Southeast due to the developing El Niño. However, much of the northern tier of states could trend hotter due in part to El Niño.

Hurricane Season

El Niño can also be one of the strongest influences on hurricane season.

In El Niño hurricane seasons, stronger shearing winds often occur over at least the Caribbean Sea and some adjacent parts of the Atlantic Basin.

This tends to limit the number and intensity of storms and hurricanes, especially if the El Niño is stronger, as we investigated in a March article.

Storms this season could get squashed in the southern Gulf of Mexico and Caribbean Sea due to El Niño-enhanced wind shear and sinking air, while more typical activity roams the rest of the Atlantic from off western Africa to the Bermuda Triangle.

Winter 2023-24

Most El Niños hit their peak in late fall or winter and thus have their strongest influence on weather patterns in the colder months.

T​he classic El Niño winter is rather warm from Alaska into western and central Canada and then into the northern tier of states from the Pacific Northwest to the western Great Lakes.

I​t tends to be colder and wetter than average through much of the southern U.S., particularly from Texas to the Carolinas. We found that some cities in the Southwest, Southern Plains and mid-Atlantic have their snowiest winters during El Niño.

O​ther factors can and do influence winter weather patterns, including the polar vortex. But if this El Niño becomes strong, this may be the general picture to expect next winter.

Global Temperatures

NOAA's ENSO blog noted the warmest year of any decade tends to occur during an El Niño.

B​ut the planet's warming now means that even recent La Niña years have become warmer than El Niño years in past decades, as the graph below illustrates.

I​n fact, May 2023 was the planet's second-warmest May, according to an analysis from the European Centre for Medium-Range Weather Forecasts.

S​o it's certainly possible that 2023 could end up topping the record-warm year of 2016.​ NOAA's calculations as of their April report give about a 25 percent chance of doing so.

M​ORE ON WEATHER.COM:

S​ummer 2023 Outlook

2​023 Hurricane Season Outlook

H​ow El Niño Could Influence Hurricane Season

H​ow El Niño Could Influence Next Winter In California

W​hen Was The Last 'Quiet' Hurricane Season?

Jonathan Erdman is a senior meteorologist at weather.com and has been an incurable weather geek since a tornado narrowly missed his childhood home in Wisconsin at age 7. Follow him on Twitter and Facebook.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.