El Nino is officially underway. Here's what that means for the weather

A map of the Pacific Ocean showing sea surface temperature anomalies. The areas of yellow, orange and red to the west of South America show where El Niño has developed. (NASA Worldview)

After months of anticipation, El Niño has officially developed and will have a heavy hand in shaping the weather patterns around the world into 2024.

On Thursday morning, NOAA's Climate Prediction Center announced that "El Niño conditions are present and are expected to gradually strengthen into the Northern Hemisphere for the winter of 2023-24."

El Niño is a regular climate phenomenon in the eastern Pacific Ocean when water temperatures near the equator are at least 0.9 of a degree F (0.5 of a degree C) above the historical average for a three-month period. The extended period of warmth in this region of the ocean alters the jet stream and the overall weather patterns across North America.

The last time El Niño was observed was from late 2018 through the first half of 2019.

AccuWeather forecasters have been predicting the development of El Niño for months, with Senior Meteorologist and Long-Range Specialist Paul Pastelok talking about the potential for it to develop as far back as February during the release of AccuWeather's annual spring forecast for the United States.

This is a sharp turnaround from the past three years when El Niño's cooler counterpart La Niña reigned supreme over the Pacific Ocean.

In the summer and autumn, El Niño can help to suppress tropical activity in the Atlantic Ocean. This is one factor that AccuWeather long-range forecasters considered when they released the 2023 Atlantic hurricane season forecast.

In general, an El Niño pattern favors a more active storm track farther south across the U.S. and drier weather across northern areas.

During the winter, El Niño can promote wet weather across California and the Gulf Coast while much of the central and midwestern U.S. tends to experience milder weather with less frequent snow.

The large area of warm water in the Pacific Ocean can also help the global average sea surface temperatures to reach unprecedented levels.

The onset of El Niño is just the beginning.

NOAA says there is an 84% chance that it will become at least moderately strong by the end of 2023 or the start of 2024, meaning that it will have a bigger influence on global weather patterns. It will likely become stronger than the most recent El Niño four years ago.

The strongest El Niño on record occurred during the winter of 2015-16, barely edging out the one that unfolded during the winter of 1997-98.

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