(WGHP) – Last week the Climate Prediction Center issued an El Niño advisory stating, “El Niño conditions are present and are expected to gradually strengthen into the Northern Hemisphere winter 2023-24.”
Since that announcement, FOX8 has received phone calls asking what effects El Niño could have on the Triad during the winter months.
According to the Climate Prediction Center, El Niño’s influence on the United States is generally weak during the summer months but becomes more pronounced during the fall and winter. A moderate to strong El Niño is forecast to be in place by this winter.
So, let’s dive into what that means for the United States as a whole and what the Triad can generally expect.
What is El Niño?
To understand El Niño, it’s important to know what “normal” conditions are in the Pacific Ocean.
According to NOAA, normally the trade winds blow from west to east along the equator. As the winds blow west to east, it takes the warm water off the west coast of South America towards Asia. The warm water off the coast is then replaced with cold water that rises from the depths of the ocean in a process known as upwelling.
El Niño is a climate pattern where the trade winds, blowing from west to east, weaken over the Pacific Ocean. When the trade winds weaken, the warm water that normally shifts west towards Asia, is pushed back east toward the west coast of the Americas.
The image below shows how we know El Niño is now in place. The blue and white colors show the cooler or near-normal sea surface temperatures progressively getting warmer and shifting to a red or orange color.
The red and orange colors represent warmer-than-average sea surface temperatures along the west coast of the Americas. This indicates El Niño conditions are in place.
Since the water temperatures are now warmer than normal in the eastern Pacific, this can affect the weather in the United States significantly.
How does El Niño change the weather pattern across the U.S.?
Since El Niño causes a shift in warm waters over the Pacific Ocean, it then creates a chain reaction that impacts our weather in the United States. The warmer waters cause a shift in the Pacific jet stream, causing it to move further south than its normal position over the Pacific Northwest.
According to NOAA, this shift leads to areas in the northern U.S. and Canada seeing drier and warmer than normal conditions.
Since El Niño impacts the position of the Pacific jet stream, this means that the path storms typically take also changes. NOAA states that during El Niño, a dip in the jet stream is present in the Eastern Pacific.
The dip in the jet stream is also known as a trough which is known for causing wetter conditions in the area it occurs over. In a strong El Niño, like what’s forecast for the fall and winter of 2023, the dip in the jet stream occurs further east in the Eastern Pacific.
This eastward shift means it’d likely be positioned to bring large amounts of tropical moisture into California instead of the normal position of the Pacific Northwest.
In a strong El Niño, rainfall in California can be significantly above normal which may lead to flash flooding or even landslide or mudslides.
According to the National Weather Service, California isn’t the only state that may be wetter than normal. In fact, most of the southern United States including the Gulf Coast and the Southeast see above-normal precipitation through the winter months.
During a strong El Niño event, drier-than-normal conditions are more likely in the Ohio and Tennessee Valleys as well as the Pacific Northwest.
The position of the Pacific jet stream can also lead to warmer-than-normal temperatures in the northern half of the United States and cooler-than-normal temperatures across the southern half of the country.
How could the Triad’s weather be impacted in winter 2023-2024?
Since a strong El Niño is forecast for fall 2023 and winter 2023-2024, the Triad and North Carolina are forecast to see wetter-than-normal conditions and cooler-than-normal temperatures.
The images below show the temperature and precipitation difference during past strong El Niño events compared to the long-term average.
The temperature anomalies during strong El Niño years compared to the long-term average show the warmer-than-normal temperatures that typically occur in the northern half of the United States. The warmer-than-normal temperatures are depicted with orange and red colors.
The cooler-than-normal southern United States is depicted with green and blue colors. The Triad and North Carolina show temperatures averaging around one to two degrees cooler than normal from November through March.
The precipitation anomalies during a strong El Niño year show wetter-than-normal conditions across the southern United States and along the majority of the East Coast. The green and blue colors represent the wetter-than-normal conditions.
The yellow, orange and red colors depict the drier-than-normal conditions in the Pacific Northwest and the Ohio and Tennessee Valleys.
From this image, we learn that the Triad has a history of one to two inches above normal precipitation from November to March during a strong El Niño year.
While we won’t know actual numbers until we get closer to the fall and winter months, looking back at strong El Niño years helps us infer that this upcoming winter particularly, the Triad can expect an overall cooler and wetter pattern.