El Niño strengthens, raising new questions for Minnesota’s winter
Increased confidence that a very strong El Niño could shape the upcoming winter.
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The latest update from the National Oceanic Atmospheric Administration (NOAA) is raising the stakes for the upcoming winter.
El Niño has officially arrived in the tropical Pacific, and the event is strengthening quickly. In its latest El Niño Southern Oscillation (ENSO) diagnostic discussion issued Aug 13, NOAA’s Climate Prediction Center says there is now greater than a 90 percent chance that a very strong El Niño will persist through the Northern Hemisphere fall and winter.
More strikingly, NOAA is giving a 69 percent chance that the October through December period could reach a historically strong El Niño threshold.
That would make this much more than an ordinary El Niño event.
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The Pacific is warming quickly
The ocean temperatures across the equatorial Pacific have continued to climb throughout the summer. In July, the Niño 3.4 region, the area most commonly used to classify El Niño and La Niña, averaged about 1.4 degrees Celsius above normal.
The strongest warmth is currently located farther east. Sea-surface temperatures (SST) in the eastern tropical Pacific have been more than 2 degrees Celsius above normal, while the region immediately off the coast of South America has been even warmer.
Our atmosphere is responding
One of the biggest developments in recent weeks is that the atmosphere is now showing signs of El Niño. Thunderstorms have increased across the central and eastern Pacific, while storm activity has decreased near the western Pacific.
This is important because El Niño isn't just about warmer ocean temperatures. The ocean and atmosphere need to work together for El Niño to become a major climate pattern.
Right now, that appears to be happening. The ocean and atmosphere are feeding off each other, which helps explain why NOAA's confidence in a very strong El Niño has risen so much.
What could this mean for Minnesota?
For Minnesotans, the obvious question is what all of this means for the upcoming winter.
Historically, El Niño has tilted the odds toward a milder and less snowy Minnesota winter. According to an updated analysis from the Minnesota Department of Natural Resources (DNR), the 27 El Niño winters since 1950 have averaged 2.4 degrees Fahrenheit warmer statewide than non-El Niño winters. In the Twin Cities, seasonal snowfall has averaged about 24 percent less during El Niño winters.
But that doesn't mean winter weather disappears. Far from it. The DNR notes that even during some of the strongest El Niño events on record, Minnesota experienced major snowstorms and blizzards. The Halloween Blizzard of 1991 occurred during a very strong El Niño, while the record-strength 1982–83 event produced two significant blizzards.
The takeaway is that El Niño changes the odds, but it doesn't write the forecast for every storm. Minnesota can still see Arctic outbreaks, major snowstorms and stretches of classic winter weather, even during a potentially historic El Niño.
The bigger question is what happens next
At this point, forecasters aren't asking whether El Niño will develop. It already has.
The big question is how strong El Niño becomes and how it affects the atmosphere across the Northern Hemisphere. Other factors, such as the jet stream and other weather patterns, will also play a role in Minnesota’s winter weather.
Those features can either reinforce or counteract the typical El Niño pattern.
That is why an ENSO forecast is best viewed as a change in probabilities rather than a guarantee of a particular winter.
Still, the latest NOAA update is significant.
The Pacific has warmed rapidly, the atmosphere is now responding, and NOAA has very high confidence that this will become a very strong El Niño event.
For Minnesota, that raises the odds of a warmer-than-average winter and potentially less overall snowfall, but it certainly doesn't take snowstorms or Arctic air off the table.
And with the strongest part of the event still developing, the evolution of El Niño over the next few months will be something meteorologists will be watching very closely.
