NOAA forecasts a "very strong" El Niño developing in the equatorial Pacific, possibly among the strongest in the modern record, yet the scientists tracking it concede the climate pattern's interaction with the polar vortex remains an open question with no reliable answer.
The federal agency's characterization lands at a moment when Americans from the mid-Atlantic to the Pacific Northwest are trying to plan for a winter season that could swing between unusual mildness and punishing cold, depending on atmospheric forces that even top researchers describe in terms of probability, not certainty. Four scientists from NOAA, MIT, Johns Hopkins, and the University of Miami each offered USA TODAY variations on the same theme: we know a strong El Niño changes things, but we cannot tell you exactly how.
That gap between confident headlines and honest uncertainty matters. Families budget for heating bills. Municipalities plan salt and plow contracts. Farmers hedge crop insurance. When the nation's premier weather agency says a major climate driver is building toward historic strength, the practical question is not whether El Niño is real. It is whether anyone can tell you what it will do to your winter, and right now, the answer is a qualified no.
El Niño forms along the equatorial Pacific and reshapes pressure patterns across the troposphere, the lowest layer of the atmosphere. Those pressure shifts alter the jet stream, which in turn can strengthen or weaken the polar vortex, a mass of cold air spinning above the Arctic that forms each fall as temperatures drop.
Amy Butler, a physicist at NOAA's Chemical Sciences Laboratory, told USA TODAY by email that El Niño tends to weaken the polar vortex in mid-to-late winter. A weakened vortex raises the odds of sudden stratospheric warming events, episodes that can last several weeks and push their effects downward, reinforcing cold surface temperatures and weather patterns across the United States and Europe.
The El Niño now building toward potentially record territory adds a layer of difficulty. Stronger El Niño events exert greater force on these planetary systems, but greater force does not mean greater predictability.
Darryn Waugh, a professor of Earth and Planetary Sciences at Johns Hopkins University, framed the science in careful terms. Both the polar vortex above the Arctic and the jet stream can be affected by El Niño, he said, but the chain of cause and effect is not guaranteed.
"It's when this happens, there's an increased probability that something will happen."
Waugh's point is worth sitting with. Scientists cannot say that when El Niño does X, the polar vortex always does Y. They can say the odds shift. For a homeowner in Philadelphia or a rancher in eastern Oregon, "increased probability" is not the same as a forecast you can act on.
Judah Cohen, a polar vortex expert at MIT, laid out two broad scenarios. If the polar vortex stays strong through the coming winter, the season will be mild overall regardless of El Niño, with the possible exception of the West Coast. But if El Niño weakens the vortex and triggers sudden stratospheric warming, the result could mirror the severe winter weather that hammered the mid-Atlantic during the 2019, 2020 season.
Cohen was also direct about the limits of current knowledge. Scientists do not yet fully understand the relationship between El Niño and the polar vortex, he said. The patterns interact, but the relationships are not particularly strong, a candid admission from one of the country's leading researchers on the subject.
That candor stands in contrast to the way climate forecasts often land in public debate, where probability gets flattened into certainty and caveats disappear by the second news cycle. NOAA itself has already adjusted its outlook on related weather patterns this year, cutting its Atlantic hurricane forecast as the El Niño signal strengthened and suppressed tropical storm activity.
Ben Kirtman, dean of the Rosenstiel School of Marine, Atmospheric and Earth Science at the University of Miami, introduced a complication that deserves more attention than it usually gets. If this El Niño proves historically strong, its effects on the larger atmosphere remain a genuine unknown, because it is arriving on top of a warming climate that may alter how these systems talk to each other.
"This is an El Niño superimposed on top of a pretty big climate change signal."
Kirtman went further, noting that scientists lack a clear understanding of how the warming backdrop changes what meteorologists call teleconnections, the long-distance links between weather patterns in different parts of the globe.
"We don't have a clear understanding how that changes the teleconnections, those relationships. That's an open science question."
An "open science question" is an honest phrase. It is also the kind of phrase that rarely survives contact with policy advocacy or media shorthand. When NOAA forecasts historic El Niño strength, the temptation, in government, in media, in advocacy, is to project certainty that the underlying science does not support.
The broad regional tendencies during an El Niño winter are well established. The southern United States tends to see wetter-than-average conditions. The Great Lakes region, interior New England, and the Pacific Northwest tend to see less snow. The eastern United States faces the risk of Arctic air funneling south when the polar vortex weakens.
But "tends to" is doing heavy lifting. Each of those regional patterns is a statistical average drawn from past El Niño events. A "very strong" El Niño, one that NOAA says could rank among the strongest in the modern record, may not follow the average playbook. Kirtman's point about the climate change overlay makes that uncertainty sharper, not softer.
For American households already facing elevated energy costs, the practical stakes are real. A winter shaped by a weakened polar vortex could drive heating demand well above normal across the eastern half of the country, while a strong-vortex scenario would keep things mild. The difference between those two outcomes is not academic, it shows up in utility bills, in road budgets, and in household energy costs that families cannot easily absorb.
The scientists quoted in this reporting deserve credit for something increasingly rare in public discourse: acknowledging the boundaries of their own expertise. Waugh talked about probability, not certainty. Cohen called the relationships "not particularly strong." Kirtman called the central question "open." Butler described tendencies, not guarantees.
That restraint is worth more than a dozen confident predictions. The El Niño now building in the Pacific is already reshaping weather systems, Pacific storm activity has intensified as the pattern strengthens. Its effects on the coming winter will be significant. But the honest answer, from the people who study this for a living, is that the specifics remain uncertain.
Americans can handle uncertainty. What they cannot handle, and should not have to, is uncertainty dressed up as settled science to serve someone else's agenda.
