What would an El Niño mean for Utah this summer?
The emerging El Niño weather pattern probably isn’t going to bring big changes to Utah’s weather this summer. But the first change it might deliver wouldn’t be good news for a state still dealing with ongoing drought: a shorter, drier monsoon season.
The National Oceanic and Atmospheric Administration recently issued an El Niño watch, reporting a more than 60% chance of this pattern developing by early summer. And it’s almost certain — a nearly 90% chance — that it’ll arrive by the end of this year.
El Niño is the warm phase of a cyclical climate pattern known as the El Niño-Southern Oscillation, when temperatures in the Pacific reach more than 0.5 degrees Celsius above normal.
So how does El Niño — which originates in the tropical Pacific Ocean — impact Utah’s weather at all?
Jon Meyer, assistant state climatologist with the Utah Climate Center and Utah State University, said southern Utah piggybacks off El Niño’s strong connection to weather in the desert Southwest. Fewer rain clouds in the southern Utah atmosphere, he said, would likely mean less moisture makes its way up to northern Utah this summer too.
“Right now,” Meyer said, “we are hedging our bets toward a delayed onset and potentially a drier overall summer monsoon for all of Utah as a function of El Niño.”
He wouldn’t be surprised if El Niño pushed the beginning of monsoon season back a week or two behind its usual early July start date in southern Utah, likely leading to fewer weeks — and fewer inches — of summer precipitation.
That’s what happened the last time Utah experienced a strong El Niño in 2016. That year, the monsoon season’s delayed start and drier-than-average rain totals fueled dangerous wildfire conditions and extreme heat across the state.
As the year goes on, Emily Becker, a climate scientist at the University of Miami who writes about El Niño for NOAA, said the weather pattern generally leads to more winter precipitation for the southern U.S. as it extends the Pacific jet stream and holds it in place from southern California to the Gulf Coast.
“It tends to bring the storms more consistently across the southern tier of the U.S.,” Becker said, “instead of sort of letting them just hit anywhere they feel like.”
If southern Utah can catch some of that moisture traveling across the southern jet stream, that could mean a wetter-than-average winter — good news for the dry region.
While Becker said that does mean there’s an improved chance of drought relief under El Niño, it’s still a long way from solving the problem.
“I certainly wouldn't advise assuming that drought is done,” Becker said. “[Water scarcity is] an ongoing issue, regardless of what phase of El Niño or La Niña we have.”
She said there’s roughly a 40% chance of this year’s weather pattern elevating into a strong El Niño. That doesn’t necessarily lead to more severe weather effects, just a more consistent pattern of predictability.
Historical data from previous strong El Niño events might give us some clues about what that could mean for Utah. But Alex DeSmet, a meteorologist with the National Weather Service office in Salt Lake City, said predicting weather months in advance is a tough call.
“No two El Niño events are the same,” DeSmet said. “If you look back at the last five strong El Niños, there's a mixed bag."
During the last strong event in 2015-2016, he said, Utah saw average precipitation across the state. In the one before that, in 1997-1998, northern Utah had slightly above-average moisture.
But the historical El Niño that might be the best comparison for this year, DeSmet said, is 1982-1983. Back then, Utah came out of a La Niña winter with an above-average snowpack — similar to how the state is set up now. That year, Utah also saw above-average precipitation and flooding across the state.
But even if El Niño begins early this summer, it’s possible Utahns may not notice.
For one, it could take several weeks after ocean temperatures hit the El Niño threshold for the effects to ripple their way into Utah’s atmosphere. On top of that, Utah tends to feel El Niño’s effects more in the late fall and winter than it does in the summer.
And unlike most other western states, Utah’s weather doesn’t typically sway too far in one direction or another during El Niño. It’s caught in the middle geographically, between the typically drier, warmer weather this pattern brings to the northern U.S. and the wetter, cooler weather down south.
But for the people tasked with predicting the weather and helping Utahns stay prepared, like Meyer at the Utah Climate Center, that lack of certainty still leaves things vexingly up in the air.
“I wish that we did have a better relationship with El Niño,” Meyer said. “We have a very diverse and dynamic climate here in Utah, and having limited predictability makes it that much more challenging.”