Transition of El Niño and La Niña with intermediate neutral phase likely in June-August 2024 US National Weather Service ABPP
The transition from El Niño to La Niña is likely to occur from June to August this year, with a neutral El Niño-Southern Oscillation (ENSO) event occurring from April to June. There is a 79 percent chance of a transition from El Niño to a neutral state of El Niño variability anytime between April and June, and a 55 percent chance of a La Niña event in June and August, the US National Weather Service’s Climate Prediction Center said on February 8. , 2024.
El Niño is the warm phase of the El Niño-La Niña climate pattern, also known as ENSO, and is one of the most important climate phenomena on Earth due to its ability to alter the global atmospheric circulation. This in turn affects temperature and precipitation around the world.
El Niño consists of three phases: El Niño, “neutral,” and La Niña. El Niño and La Niña are two opposite phases, and they occur as a result of changes in both the ocean and the atmosphere because El Niño is a dual phenomenon.
ENSO includes the central Pacific region.
When conditions in the Pacific are normal, trade winds blow from east to west along the equator, carrying warm waters from South America toward Asia. Cold water rises from the depths to replace this warm water. This process is called volatility. El Niño and La Niña conflict with climate patterns that break these natural conditions, and have global impacts on weather, ecosystems, wildfires, and economies.
El Niño and La Niña occur every two to seven years, on average, and typically last nine to 12 months, but can sometimes last for years.
In 2023, El Niño conditions develop by early June.
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What is the El Niño phenomenon?
El Niño refers to ocean surface warming, or above-average sea surface temperatures in the central and eastern Pacific Ocean, a phenomenon that changes the global atmospheric circulation in known ways. As a result, climate scientists can predict likely upcoming weather and climate patterns.
Trade winds weaken during El Niño, pushing warm water eastward toward the west coast of the Americas.
According to the Naval Postgraduate School, normal conditions are such that a warm pool of ocean water accumulates in the western tropical Pacific because the trade winds blow from east to west. There is a pressure gradient between the western Pacific and the eastern Pacific, with the former having lower pressure and the latter having higher pressure. Because of this pressure gradient, the trade winds move from east to west. They are called the eastern trade winds.
When El Niño conditions develop, surface pressure weakens, and the trade winds reverse. As a result, warm water propagates eastward via Kelvin waves, a special type of gravitational wave affected by Earth’s rotation that occurs at the equator and along lateral vertical boundaries such as coastlines or mountain ranges.
As warm water pushes eastward toward the west coast of the Americas, the thermocline descends. The transition layer between the warmer mixed water at the surface and the cooler deep water below is called the thermocline.
A sinking thermocline causes upwelling, or the rise of cold water from the depths, deeper in the ocean.
According to the Marine Postgraduate School, this is critical on the western coasts of the Americas, because without rising nutrient-rich bottom waters, fish populations would decline dramatically.
El Niño has been observed and recorded at least since the 17th century, off the coast of Peru. Due to the occasional appearance of abnormally warm water around Christmas, Peruvian fishermen named the phenomenon “El Nino de Navidad,” which means “Christ Child” in Spanish.
What is the La Niña phenomenon?
La Niña refers to ocean surface cooling, or below-average sea surface temperatures in the central and eastern tropical Pacific Ocean.
La Niña tends to increase rainfall over Indonesia, and decrease it over the central tropical Pacific.
La Niña is the opposite of El Niño. A La Niña phenomenon is one in which the trade winds are stronger than usual, and as a result more warm water is pushed westward, toward Asia. As easterly winds along the equator become stronger and warm water pushes westward toward Asia, bottom water is rising to the surface off the west coast of the Americas, and cold, nutrient-rich water is rising to the surface. A strong pressure gradient drives the movement of trade winds.
Cold water moves toward the west coast of the Americas via Rossby waves, which occur naturally in rotating fluids. Also known as planetary waves, Rossby waves are formed within the Earth’s atmosphere and oceans as a result of the planet’s rotation.
Since the trade winds are stronger than usual, the pool of warm water formed in the western Pacific Ocean is shifted further west.
“La Niña” means “the little girl” in Spanish, and is sometimes called “El Viejo,” which means “the cold one.”
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