Forecast says El Niño will be strong this winter. Here’s what it means for Idaho weather
A new forecast shows warmer and dryer weather than usual is on target for Idaho this winter as El Niño gains strength.
Strong El Niño conditions are favored for this winter, which could impact weather conditions in Idaho and across much of the U.S., according to the latest National Oceanic and Atmospheric Administration forecast.
Officials declared that El Niño had begun in June, and the weather phenomenon has gained strength ever since. NOAA forecasters predict a 75-85% chance of a strong El Niño from November through January. There is an 80% chance El Niño will last through spring.
NOAA adds there is also a 3-in-10 chance that this El Niño could become “historically strong” and rival 2015-16 and 1997-98 events.
Can El Niño and La Niña impact the Northwest?
El Niños and their opposites, La Niñas, are naturally occurring weather phenomena that usually alternate every couple of years as a function of how the Pacific Ocean interacts with the air above it.
A La Niña occurs when the temperature of the sea is cooler than average in the eastern Pacific Ocean, resulting in less evaporation, weaker storms and less moisture in the atmosphere, according to NOAA.
We underwent a historic three-straight years of La Niñas, from 2020 to 2023, a rarity that’s only happened on two other occasions in recorded history, according to National Weather Service meteorologist Dave Groenert. The other two recorded times are 1973 to 1976 and 1998 to 2001.
“It typically ping pongs back and forth, in general, from one to neutral to the other and back,” Groenert told the Idaho Statesman. “Sometimes you do get return years, but to get a third return year, I don’t know if anyone really knows as to why that’s the case.”
El Niño occurs when trade winds — the permanent east-to-west winds that blow near the equator — weaken, allowing the Pacific Ocean’s warmer waters to push back east toward the United States West Coast.
This weakening allows the Pacific jet stream to dip farther south, amplifying the storm track across the southern U.S. and Central America but keeping stronger tropical moisture away from the north.
“El Niño — the warm phase of the El Niño-La Niña climate pattern — changes global atmospheric circulation in known ways, giving us an idea of potential upcoming weather and climate patterns,” NOAA stated in a June news release. “A stronger El Niño means global temperature, rain and other patterns are more likely to reflect the expected El Niño impacts.”
How could a strong El Niño impact Idaho?
According to the U.S. Department of Agriculture, a stronger El Niño could cause less rainfall and warmer temperatures than average during winter in Idaho, and the rest of the Pacific Northwest.
According to the Climate Prediction Center, most of Idaho has a 40-60% chance of above-average temperatures and a 33-50% chance of below-average rainfall from November through January.
From November through January, Boise typically sees an average of 4.13 inches of precipitation and 12.9 inches of snow, meaning totals will likely be lower than those two figures for the upcoming winter.
This story was originally published October 25, 2023 at 12:57 PM.
