La Ni帽a is coming, raising the chances of a dangerous Atlantic hurricane season鈥揳n atmospheric scientist explains this climate听phenomenon
One of听听to the record-breaking global temperatures over the past year鈥�El Ni帽o鈥�, and its opposite, La Ni帽a, is on the way.
Whether that鈥檚 a relief or not depends in part on where you live. Above-normal temperatures are still听. And if you live along the U.S. Atlantic or Gulf coasts, La Ni帽a can contribute to the听.
Pedro DiNezio, a University of Colorado Boulder associate professor of atmospheric and ocean sciences听who studies El Ni帽o and La Ni帽a, explains why and what鈥檚 ahead.
Pedro DiNezio is听a University of Colorado Boulder associate professor of atmospheric and ocean sciences听who studies El Ni帽o and La Ni帽a.
What is La Ni帽a?
La Ni帽a and El Ni帽o are the two extremes of a听听that can affect weather around the world.
Forecasters know La Ni帽a has arrived when temperatures in the eastern Pacific Ocean along the equator west of South America cool by听听(0.9 Fahrenheit) below normal. During El Ni帽o, the same region warms instead.
Those temperature fluctuations might seem small, but they can affect the atmosphere in ways that ripple across the planet.
The tropics have an atmospheric circulation pattern called the听, named after Sir Gilbert Walker, an English physicist in the early 20th century. The Walker Circulation is basically giant loops of air rising and descending in different parts of the tropics.
Normally, air rises over the Amazon and Indonesia because moisture from the tropical forests听, and it comes down in East Africa and the eastern Pacific. During La Ni帽a, those loops intensify, generating stormier conditions where they rise and drier conditions where they descend. During El Ni帽o, ocean heat in the eastern Pacific instead shifts those loops, so the eastern Pacific gets stormier.
EL Ni帽o and La Ni帽a also affect听, a strong current of air that blows from west to east across the U.S. and other mid-latitude regions.
During El Ni帽o, the jet stream tends to push storms toward the听, making these typically dry areas wetter. Conversely, mid-latitude regions that normally would get the storms become drier because storms shift away.
This year, forecasters expect a听听鈥� likely by late summer. After a strong El Ni帽o, like the world saw in late 2023 and early 2024, conditions tend to swing fairly quickly to La Ni帽a. How long it will stick around is an open question. This cycle tends to swing from extreme to extreme every听, but while El Ni帽os tend to be short-lived, La Ni帽as can last two years or longer.
How does La Ni帽a affect hurricanes?
Temperatures in the tropical Pacific also control wind shear over large parts of the Atlantic Ocean.
Wind shear is a difference in wind speeds at different heights or direction. Hurricanes have a harder time holding their column structure during strong wind shear because stronger winds higher up push the column apart.
La Ni帽a produces less wind shear, removing a brake on hurricanes. That鈥檚 not good news for people living in hurricane-prone regions like Florida. In 2020, during the last La Ni帽a, the Atlantic saw a听听and 14 hurricanes, and 2021 had 21 tropical storms and seven hurricanes.
Forecasters are already warning that听听肠辞耻濒诲听, due in large part to La Ni帽a. The tropical Atlantic has also been exceptionally warm, with听听for over a year. That warmth affects the atmosphere, causing more atmospheric motion over the Atlantic, fueling hurricanes.
During La Ni帽a, the Walker Circulation intensifies, triggering stronger storms where the air rises. (Graphic: Fiona Martin/NOAA Climate.gov)
Does La Ni帽a mean drought returns to the US Southwest?
The U.S. Southwest鈥檚 water supplies will probably be OK for the first year of La Ni帽a because of all the rain over the past winter. But the second year tends to become problematic. A third year, as the region saw in 2022, can lead to听.
Drier conditions also fuel听听in the West,听, when the winds pick up.
What happens in the Southern Hemisphere during La Ni帽a?
The impacts of El Ni帽o and La Ni帽a are almost a mirror image in the Southern Hemisphere.
Chile and Argentina tend to get drought during La Ni帽a, while the same phase leads to more rain in the Amazon.听听during the last La Ni帽a. La Ni帽a also听, meaning above-average rainfall. The effects aren鈥檛 immediate, however. In South Asia, for example, the changes tend to show up a few months after La Ni帽a has officially appeared.
La Ni帽a is听, where vulnerable communities are already in a听.
Is climate change affecting La Ni帽a鈥檚 impact?
El Ni帽o and La Ni帽a are now happening on top of the effects of global warming. That can exacerbate temperatures, as the world saw in 2023, and precipitation can go off the charts.
Since summer 2023, the world has had听听of record-breaking global temperatures. A lot of that warmth is coming from the oceans, which are听.
La Ni帽a should cool things a bit, but听听that drive global warming are still rising in the background. So while fluctuations between El Ni帽o and La Ni帽a can cause听, the overall trend is toward a warming world.
Pedro DiNezio is an associate professor of atmospheric and oceanic sciences听at the听.
This article is republished from听听under a Creative Commons license. Read the听.
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