El Niño is the last season.
Federal forecasts say the climate pattern, which brought warmer-than-normal ocean temperatures to the Eastern Pacific — and helped push global temperatures to new highs — starting in June 2023, has officially ended.
The National Weather Service’s Climate Prediction Center announced Thursday that neutral conditions returned over the past month, as expected.
But it won’t last long: El Niño’s cooler counterpart, La Niña, is forecast to develop this summer and linger throughout the Northern Hemisphere’s winter.
“The tropical Pacific climate pendulum appears to be swinging back to the other extreme,” read a Thursday post on the National Oceanic and Atmospheric Administration’s (NOAA) ENSO blog, which focuses on this particular phenomenon.
La Niña brings unusually cold ocean temperatures to the Pacific, with implications for weather around the world. The NWS says there is a 65% chance it will arrive between July and September and an 85% chance it will stick around until January 2025.
Forecasters initially predicted that La Niña could start as early as June, but changed the timeline as the rate of cooling continued.
That means they can come in well during the peak of the Atlantic hurricane season — and that could add to it.
La Niña conditions are particularly conducive to Atlantic storms
NOAA has predicted an 85% chance of an above-normal hurricane season, which runs from June to November. In the past month, between 17 and 25 storms have been named – the largest number of storms the agency has predicted this season. (There will be 20 hurricanes in 2023, the fourth highest year since 1950.)
Forecasters point to several factors, including warm ocean temperatures in the Atlantic and the development of La Niña conditions in the Pacific.
La Niña historically enhances Atlantic hurricane activity by reducing vertical wind shear in the tropics. Strong wind shear, which occurs when wind conditions change rapidly, causes developing storms.
Consider this: La Niña typically means stronger hurricane activity in the Atlantic basin and less hurricane activity in the central and eastern Pacific basin. El Niño achieves the opposite.
“The hurricane effects of El Niño and its La Niña counterpart look back and forth between the Pacific and Atlantic oceans, strengthening hurricane activity in one region while weakening another,” according to a 2014 ENSO blog post.
Interestingly, the NWS notes that some of the most destructive hurricanes to hit the US in recent decades – like Katrina in 2005 and Andrew in 1992 – did not occur during La Niña, but in the neutral phase of the cycle.
What La Niña means for winter in the US
After hurricane season wraps up, La Niña may play a role in winter weather across the US, bringing warmer-than-average temperatures to the South and cooler-than-average temperatures to the North.
As NOAA explains, its arrival in the Pacific Ocean causes changes in tropical rainfall and wind patterns that have ripple effects around the world. In the US, there are usually changes in the mid-latitude jet stream, which affects temperature and precipitation.
“During La Niña, the Pacific jet stream often flows into the North Pacific and is less reliable over the southern United States,” the agency said.
As a result, southern and interior Alaska and the Pacific Northwest can be colder and wetter than normal, and the southern part of the country – from California to the Carolinas – tends to be extra warm and dry. The Ohio and Upper Mississippi River Valleys were also wetter than usual.
La Niña also makes waters in the Pacific cooler and more nutritious than usual, which draws cold-water species — think squid and salmon — to the coast of California and other locations, the National Ocean Service said.
La Niña conditions are also associated with a higher frequency of spring tornadoes in the central US
The NWS said La Niña and El Niño tend to be strongest from December to April, “because equatorial Pacific sea surface temperatures are typically warmest around this time.”
A more detailed prediction of La Niña may be on the horizon, as NOAA plans to release its next forecast in mid-July.
Global temperatures are still rising, even in cooler climate patterns
It is important to remember that climate patterns like La Niña and El Niño, which naturally fluctuate, occur in the context of human-induced climate change – which makes weather more extreme around the world.
The World Meteorological Organization said earlier this month that the past nine years were the warmest on record, despite the “cooling effect of a multi-year La Niña from 2020 to early 2023.” In fact, 2023 is the hottest year on record.
WMO Deputy Secretary General Ko Barrett said in a statement that the weather will continue to be extreme because of the extra heat and moisture in the atmosphere.
“The end of El Niño does not mean a pause in long-term climate change because our planet will continue to warm due to heat-trapping greenhouse gases,” he said. “Extremely high sea surface temperatures will continue to play an important role over the coming months.”
Scientists predict that 2024 will be one of the five hottest years on record, bringing hot summers and the potential for climate-induced disasters.
Names – and phenomena – are explained
Scientists insist that La Niña is not a storm that hits a specific area at a specific time. However, it is the changes in the global atmospheric circulation that affect the weather around the world.
“Think about how a large construction project across the city could change the flow of traffic near your home, with people re-routed, side streets with more traffic, and normal exit and on-ramps closed,” NOAA’s website says. . “Different neighborhoods will be most affected at different times. You will feel the effects of a construction project through a change to normal patterns, but you would not expect a construction project to ‘hit’ your home.”
It is part of the El Niño-Southern Oscillation (ENSO) cycle, a natural climate pattern defined by opposing warm and cold phases of oceanic and atmospheric conditions in the Pacific. In the ENSO cycle, La Niña and El Niño repeatedly cool and warm tropical oceans on average every two to seven years.
Forecasters can officially declare a La Niña event when sea surface temperatures drop below a certain level, modeled to stay within that threshold and provide a visible atmospheric response, such as wind changes.
As for the name: South American fishermen have long observed warmer than normal Pacific Ocean coastal waters and a dramatic decrease in fish catches around Christmastime.
They dubbed the phenomenon El Niño – Spanish for “the little boy” – after the baby Jesus. So when scientists discovered the opposite phase of El Niño in the 1980s, they called it “the little girl,” or La Niña.