It all begins far out over the Pacific, where giant bubbles of moist air rise off the warmest parts of the ocean and become entrained in writhing atmospheric streams moving west to east across the Northern Hemisphere.
Meeting with colder air, the entire mass is nudged into a counter-clockwise swirl, recognizable as a near-spiral cloud band, or a comma-shaped plug, moving toward the west coast of North America in cyclical undulations. Along with oft-mentioned phenomena like El Niño, other things are in play — decadal variations in the larger Pacific Basin, and long-distance connections with pressure changes in the Atlantic Basin.
It’s not for lack of trying that we don’t see the big picture yet. Atmospheric scientists have been studying those rhythms for centuries, for the last few decades with the help of sophisticated instruments, mounted on buoys, weather balloons, in planes and, of course, on satellites. With the help of powerful computer models and a growing database, they’re starting to unravel the mysteries, including some that directly affect our everyday lives.
That would include the El Niño-La Niña cycle, part of a rhythmic change in the pattern of Pacific Ocean sea surface temperatures that can drive changes in weather patterns around the globe, bringing drought to Australia and deluge to western South America, all in the same year.
The past few months, the weather world has been eyeing the Pacific, as giant, slow-moving masses of warm water called Kelvin waves moved eastward, tipping the equatorial region toward the formal El Niño threshold.
Those waves were among the strongest ever recorded, leading some experts to tout a possible Super El Niño that could drive average global temperatures to a new all-time high record. But according to other scientists, that scenario is far from a done deal.
Ultimately, every El Niño is different, even if there is an overall pattern.
For Colorado, the information is critical. Even slight variations in annual snowfall of 20 percent make a difference when it comes to planning water diversions and storage, and if a lengthy dry spell is on the horizon, farmers, water managers and ski area bosses want to know.
They often call on National Oceanic and Atmospheric Administration meteorologist Klaus Wolter, who has been studying those cycles for years, developing sophisticated computer models to improve long-range forecasting. From his Boulder office and his mountain home west of Boulder, he’s seen it all, from record snows to epic droughts and last September’s floods, which affected Wolter’s entire community profoundly, including spurring fears of yet more floods.
It gets to the essence of why people like Wolter dedicate their professional lives to trying to figure it all out, because with accurate information, we can prepare.
And if this year’s prediction of an early and moderately strong El Niño comes to pass, it could indeed mean more trouble for some hard-hit areas, Wolter said.
“I think I’m on board that this is going to be El Niño, and the stronger it is, the wetter this summer will be,” he says, adding that there are indications for summer moisture even without the El Niño factor. “This recent spate of wet weather on the Front Range is hinting that we’re on track for that. But we don’t really know how long this thing is going to stick around.”
Essentially, a burgeoning El Niño shifts the summer monsoonal flow, weakening it in Mexico and sending more moisture toward New Mexico, Colorado and even into southern Wyoming.
“Right now, I’m thinking a moderate El Niño, when you look at the next five months or so,” Wolter says. “Considering the floods last year, this is the one time we don’t need it,” he said, referring to the historical trend of above average summer rains when El Niños start to form in the spring and strengthen into summer.
Already, Wolter recorded the second-wettest May on record at his station near Jamestown, and extra moisture is one thing the area desperately doesn’t need this summer. Canyons scarred by last September’s torrents are exponentially more susceptible to further damage, even from less than record flows.
The state’s weather history is pretty clear on the link, with the 1976 Big Thompson flood, the 1997 Fort Collins flood and other big events all coming during El Niño onset years.
On the brigher side, it could also mean fewer intense and damaging wind storms, Wolter adds.
But a summer El Niño also increases the odds of big autumn snowstorms that can close roads and schools along the Front Range. Nearly all the big his toric fall blizzards have been during El Niño years, he says.
Looking back at the 24 years of watching weather from his mountain home, Wolter says he remains awed by the chaotic nature of the atmosphere.
“I’ve been more humbled over the years at how much natural variability is in the system — it just keeps it interesting,” he says.
Respond: letters@boulderweekly.com
