El Nino watch issued: Here’s how it could affect weather in the US
Big changes are unfolding in the Pacific Ocean, and the result could have significant implications for the Atlantic hurricane season and the upcoming winter in North America.
Sea surface temperature anomalies for April 12, 2023. Yellow, orange and red indicate where water is warmer than historical averages, and green, blue and purple show where water is cooler than historical averages. (NASA Worldview)
The Pacific Ocean is getting warmer, and the rising water temperatures have spurred forecasters to issue the first El Niño watch in years. AccuWeather meteorologists say that the emerging phenomenon will play a pivotal role in dictating the weather patterns for North America and beyond through the upcoming winter.
El Niño is part of a regular climate cycle known as the El Niño-Southern Oscillation (ENSO). It occurs when sea surface temperatures in the equatorial eastern Pacific rise to above-average levels for an extended period of time. Its cooler counterpart, La Niña, is declared when water temperatures in this zone of the Pacific Ocean are below historical averages for months at a time. When the water temperatures are right around the long-term averages, forecasters say the ENSO is neutral.
NOAA's Climate Prediction Center (CPC) issued a report on Thursday stating there is a 62% chance of El Niño developing between May and July 2023.
The last time an El Niño occurred was during the winter of 2018-2019.
AccuWeather Lead Long-Range Meteorologist Paul Pastelok said that El Niño will likely develop by late June, but it is still uncertain how strong it will become this year due to the influence of other climate phenomena.
The water temperatures near the equator in the Pacific Ocean can alter the jet stream on a global scale. The more the water in this zone warms up, the stronger El Niño becomes, resulting in a bigger influence on the jet stream.
The anticipated arrival of El Niño will align with the Atlantic hurricane season, which begins in June and ramps up in August and September. Although El Niño occurs in the Pacific Ocean, it can have a significant impact on tropical systems over the Atlantic hurricane basin.
During the Atlantic hurricane season, El Niño “creates stronger vertical wind shear across the Gulf of Mexico, the Caribbean and the tropical Atlantic,” AccuWeather Hurricane Expert Dan Kottlowski said. Wind shear is defined as changing wind speed and direction with altitude and can inhibit tropical development.
Wind shear makes it difficult for tropical cyclones to have a vertically aligned center, which prevents them from strengthening. Kottlowski explained that this is similar to a spinning top. When completely upright, a top can spin continuously without issue. However, if it is angled or tilted — such as when wind shear is present — it can unravel and come to a halt.
Outside of tropical cyclones, an El Niño can also lead to wetter conditions than usual across the southern U.S. and warmer, drier conditions in the northern U.S. Stronger El Niños can amplify those effects, leading to destructive flooding in some areas and severe drought in others.
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Even though the ENSO is trending towards El Niño conditions, the exact impacts remain to be seen. Strong El Niños have recently been observed from 1997 into 1998 and from 2015 into 2016.
The increased chance for El Niño comes after La Niña conditions were present for nearly three straight years. The unusually long-lasting nature of the phenomenon led to the unofficial nickname of a “triple-dip La Niña.” It was only the third time since the 1950s that La Niña persisted for three winters in a row.
La Niña conditions were first observed in the central Pacific in the three-month stretch from July through September 2020. The triple-dip La Niña was officially declared over in March 2023.
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