Satellite images provided by the National Oceanic and Atmospheric Administration show that on August 30, 2023, Hurricane “Idalia” (center) crossed Florida and entered Georgia, and Hurricane “Franklin” (right) moved along the eastern United States. The coast moves.
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Such was the case with last season’s El Niño phenomenon.
Federal forecasters say a weather pattern that has caused warmer than normal ocean temperatures in the eastern Pacific and pushed global temperatures to new highs since June 2023 has officially ended.
The National Weather Service’s Climate Prediction Center announced Thursday that neutral weather has returned to normal over the past month, as expected.
But they’re unlikely to last long: El Niño’s cooler counterpart, La Niña, is expected to emerge this summer and last throughout the winter in the Northern Hemisphere.
“The climate pendulum in the tropical Pacific appears to be swinging toward the other extreme,” reads a post posted Thursday on the National Oceanic and Atmospheric Administration’s (NOAA) ENSO blog, which focuses on this particular phenomenon.
La Niña brings unusually cool ocean temperatures to the Pacific Ocean, affecting weather around the world. The NWS says there’s a 65% chance it will arrive between July and September and an 85% chance it will last until January 2025.
Forecasters initially predicted that La Niña could begin as early as June, but they changed the timeline as cooling rates slowed in recent weeks.
That means she could plausibly make her grand entrance just as peak Atlantic hurricane season begins, and potentially intensify it.
Anti-Niño phenomenon particularly beneficial for Atlantic hurricanes
NOAA has forecast that there is an 85% chance of above-normal conditions during hurricane season, which runs from June to November. Last month, it predicted 17 to 25 named storms, the highest number the agency has forecast at this point in the season. (There were 20 such storms in 2023, the fourth most since 1950.)
Forecasters pointed to a number of factors, including near-record ocean temperatures in the Atlantic and the development of La Niña in the Pacific.
Historically, La Niña conditions have enhanced Atlantic hurricane activity by suppressing vertical wind shear in the tropics. When wind conditions change rapidly, strong wind shear can occur, disrupting a developing storm.
Think of it this way: La Niña typically means stronger hurricane activity in the Atlantic basin, while suppressed hurricane activity in the central and eastern Pacific basins. El Niño does just the opposite.
According to a 2014 ENSO blog post, “The hurricane effects of El Niño and its counterpart La Niña act like a see-saw between the Pacific and Atlantic Oceans, intensifying hurricane activity in one region while weakening it in the other.”
Interestingly, the National Weather Service notes that some of the most destructive hurricanes to hit the United States in recent decades, such as Hurricane Katrina in 2005 and Hurricane Andrew in 1992, did not occur during La Niña; The neutral phase of the cycle.
What La Niña means for U.S. winter temperatures
During La Niña, the Pacific jet stream often meanders into the North Pacific, as shown in this graphic from the National Oceanic and Atmospheric Administration (NOAA).
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After hurricane season ends, La Niña conditions may affect winter weather across the United States, causing above-average temperatures in the South and below-average temperatures in the North.
As the National Oceanic and Atmospheric Administration explains, its arrival in the Pacific triggers changes in tropical rainfall and wind patterns that have knock-on effects for the rest of the world. In the United States, this typically involves changes in the path of the midlatitude jet stream, affecting temperature and precipitation.
“During La Niña, the Pacific jet stream often meanders 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 are likely to be cooler and wetter than normal, while southern parts of the country (from California to the Carolinas) tend to be exceptionally warm and dry. The Ohio and upper Mississippi River valleys may also be wetter than normal.
La Niña also makes Pacific coastal waters cooler and more nutrient-rich than normal, attracting more cold-water species such as squid and salmon to the California coast and other areas, NOAA said.
La Niña is also associated with a higher frequency of spring tornadoes in the central United States
The National Weather Service says La Niña and El Niño conditions tend to be strongest between December and April “because equatorial Pacific sea surface temperatures are typically warmest during this time of year.”
More detailed predictions about La Niña may be on the horizon as NOAA plans to release its next forecast in mid-July.
Global temperatures are rising even in cooler climate patterns
It’s important to remember that naturally fluctuating climate patterns like La Niña and El Niño occur within the broader context of human-induced climate change, which is making weather around the world more extreme.
The World Meteorological Organization noted earlier this month that the past nine years have been the warmest on record, despite “the cooling effects of the multi-year La Niña phenomenon from 2020 to early 2023.” In fact, 2023 is the hottest year on record.
Co Barrett, deputy secretary-general of the World Meteorological Organization, said in a statement that extreme weather will continue to exist due to excess heat and moisture in the atmosphere.
“The end of El Niño does not mean a pause in long-term climate change, as our planet will continue to warm due to heat-trapping greenhouse gases,” she said. “Unusually high sea surface temperatures will continue to play an important role in the coming months.”
Scientists predict that 2024 will be one of the hottest five years on record, bringing another scorching summer and the potential for more climate-driven disasters.
The name and explanation of the phenomenon
Scientists emphasize that La Niña is not a storm that hits a specific area at a specific time. Instead, changes in global atmospheric circulation affect weather around the world.
A web page from the National Oceanic and Atmospheric Administration (NOAA) states: “Think about how a large construction project across town changes the flow of traffic in your neighborhood, with people being rerouted and side roads taking up more traffic than normal. Exit and entrance ramp closures. “Different neighborhoods are most affected at different times of the day. You will feel the impact of construction projects through changes in normal patterns, but you don’t expect construction projects to ‘hit’ your house. ”
It is part of the El Niño-Southern Oscillation (ENSO) cycle, a natural climate pattern determined by the opposing phases of warm and cool seasons in the Pacific Ocean and atmospheric conditions. During ENSO cycles, La Niña and El Niño alternately cool and warm large areas of the tropical ocean about every two to seven years on average.
Forecasters can formally declare a La Niña event when sea surface temperatures fall below a certain level, modeled to remain below that threshold and trigger significant atmospheric responses, such as changes in winds.
As for the name: South American fishermen have long observed warmer-than-normal waters off the Pacific coast, with catches plummeting around Christmas.
They nicknamed the phenomenon “El Niño” after baby Jesus – which means “little boy” in Spanish. So when scientists discovered the opposite phase of El Niño in the 1980s, they called it “Little Girl,” or La Niña.
