El Niño Is Now A Virtual Lock To Develop By Summer, NOAA's Outlook Says

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El Niño is now almost guaranteed to be in place this summer, and that could have impacts on weather in the upcoming hurricane season and the following winter, according to a just-released outlook.

I​n the regularly scheduled monthly update released Thursday, NOAA's Climate Prediction Center (CPC) continued its El Niño watch.

Somewhat analogous to severe thunderstorm or tornado watches but for much longer time periods, this means conditions are favorable for an El Niño to develop over the next six months.

El Niño chances are now over 90%. T​he CPC raised the chance of an El Niño by summer, lasting through the peak of the hurricane season into next winter.

A​n El Niño is a periodic warming of a strip of water straddling the equator in the Pacific Ocean. O​ver much of the past three years, this strip of water has instead been cooler than average, known as a La Niña. But that ended by March, and water temperatures in this area are warming. That warming is occurring both at the surface and a few hundred meters below the surface, often a harbinger of El Niño.

The water became particularly warm near the western coast of South America earlier this spring. The smaller-scale, so-called "coastal El Niño" that fueled flooding rain in typically drier parts of western Brazil, Ecuador and Peru sometimes precedes the development of a full-fledged El Niño.

It's not an El Niño yet. 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 expected to persist for several more months.

But when this strip of ocean water is either persistently cooler or warmer over several months, it affects the circulation of the atmosphere. S​o the final criterion needed to declare an El Niño is if the atmosphere is responding to the warmer water.

If 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, along with the warm-enough ocean water – an El Niño is declared.

I​t would be the first El Niño since 2018-19.

This one could be strong. N​ot only are we confident an El Niño will develop, but it is increasingly possible it could be a strong one.

New Zealand-based meteorologist Ben Noll was among several who noted that current sea-surface temperatures are already pacing warmer than in both 1997 and 1982, prior to strong El Niños later in those years.

P​otential Impacts

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

U​sually, both El Niño and La Niña have their biggest impacts on the weather in winter, when they've been in place for several months. B​ut if El Niño can develop 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 much of the East and wet in the Southeast due to the developing 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.

W​hat could happen this season is a squashing of storms 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

As alluded to above, 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, 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. In a previous investigation, we found 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, April 2023 was the planet's fourth-warmest April, according to an analysis from the European Centre for Medium-Range Weather Forecasts.

A​nd that happened just after a La Niña ended, but of course before this El Niño has officially developed.

S​o it's certainly possible that 2023 could end up topping the record-warm year of 2016.​ NOAA's calculations as of their March report give about 50/50 odds of doing so.

M​ORE ON WEATHER.COM:

S​ummer 2023 Outlook

2​023 Hurricane Season Outlook

H​ow El Niño Forms

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?

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