Even though Atlantic Niñas are much weaker than their Pacific counterparts, they can partially neutralize La Niñas by weakening the summer winds that contribute to upwelling and cooling of the eastern Pacific.
Why are both phenomena happening now?
In July and August 2024, meteorologists cooling was noted which appeared to be the development of the Atlantic Niña along the equator. Ocean surface winds were faint throughout most of the summer, and sea surface temperatures were quite warm until the beginning of Juneso the signs of the appearance of the Atlantic Niña were a surprise.
At the same time, waters along the equator in the eastern Pacific also cooled, Expected La Niña phenomenon there in October or November.
Getting the Pacific and Atlantic Niña combination is rare but not impossible. It’s like finding two different pendulums that are weakly coupled so that they swing in opposite directions while moving together over time. Combinations of La Niña and Atlantic Niño or El Niño and Atlantic Niña are more common.
Good news or bad news for hurricane season?
The Atlantic Niña could initially spell good news for residents of hurricane-prone areas.
Cooler than average waters off the coast of Africa may suppress the formation of African easterly wavesThese are clusters of storm activity which can develop into tropical disturbances and ultimately into tropical storms or hurricanes.
Tropical storms draw energy from the process of water evaporation associated with sultry sea surface temperatures. So cooling of the tropical Atlantic could dampen this process. That would leave less energy for storms, which would reduce the likelihood of tropical cyclone formation.
However, NOAA takes all factors into account, updates Atlantic hurricane season forecastreleased in early August, and yet an extremely lively 2024 season is still predicted. The tropical storm season usually peaks in early or mid-September.
There are two reasons behind the hard-working forecasts: close to record warm sea surface temperatures across much of the North Atlantic could strengthen hurricanes. And the expected development of a La Niña pattern in the Pacific tends to weaken wind shear—a change in wind speed with height that can rip apart hurricanes. The much stronger effects of La Niña could outweigh any effects associated with the Atlantic Niña.
Deepening the problem: global warming
Over the past two years we have seen exceptionally high ocean temperatures in the Atlantic and around most of the world’s oceans. The two Niñas will likely bring some cooling relief to some regions, but it may not last long.
In addition to these cycles, the global warming trend caused by increasing greenhouse gas emissions is causing baseline temperatures to rise and may fuel for major hurricanes.