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Mountain 101: A climatological rose by any other name
Does Colorado have a ‘monsoon season?’
John Fayhee

It’s not often that you will witness near fisticuffs over climatological terminology. But, there we were, sitting on the front deck of a watering hole in a small mountain town, watching a bank of clouds that would soon send us scurrying for cover make its way over the western ridgeline toward our Here & Now.

A man sitting a few tables over said to no one in particular, “It’s like clockwork. Every day this time, the thunderstorms move in. You can set your watch.”

“Well, they’re usually just squalls that blow in and blow out,” said another man.

“I’d like to get a job as a weather forecaster in Colorado,” chimed in yet another armchair meteorologist. “All you need to do during rainy season is predict clear skies in the morning, followed by cloudiness by lunchtime, followed by an intense thunderstorm, followed by clear skies. Classic monsoon weather pattern.”

It was the use of the word “monsoon” that ended up causing the argumentative ruckus. For a solid 15 minutes, these increasingly red-faced gents argued about whether the Colorado High Country actually has a “monsoon” season, or whether the term is used, inaccurately, as a meteorological euphemism for the more mundane-sounding “rainy season.”

Thankfully, the precipitation came in sheets before folks started breaking chairs over each other’s noggins, but, even though no blows were exchanged, the question remained. As we all know, starting generally the first week of July and ending about when the aspen leaves change, the Rockies do indeed experience regular and pretty much predictable precipitation patterns that do indeed make the job of weather forecasting seem like one of the easier gigs this side of sportscasting.

Though the weather patterns of the High Country are not as clockwork-ish as some would argue, pretty much, during summer months, sometime toward late morning/midday, clouds are going to start forming on the western horizon and, following the prevailing winds, they are going to move eastward. Then, sometime early-to-mid-afternoon, the rains will come, as will lightning, thunder and wind. Then, the weather front will pass by and the world left behind will be moist, fresh and wonderful.

Of course, sometimes the rains come later in the day, and every once in a good while, mountain dwellers will wake up to grayness and drizzle. But, by and large, Colorado’s mountain rains are as much like clockwork as dynamic weather systems can be. But are those systems accurately considered “monsoons,” as many folks assert?

The answer is a guarded “yes.”

The word “monsoon” entered the English vernacular, as one would expect, in the Sixteenth Century, during the Age of Exploration, and referred not only specifically to a certain seasonal weather pattern, but also to a specific part of the world. When your average person thinks in terms of “monsoon season,” a vision of inundated rice paddies and overflowing sewage systems in India and Bangladesh will surely emerge. That’s the part of the world where the word “monsoon” was first used — entering English by way of the Dutch bastardization of the Arabic mawsim (“season”) — and it’s the part of the world where what weather-nerds call “monsoons” are the most intense. But that’s pretty much where universal agreement on the concept of monsoons ends.

The most basic historic definition of monsoon does not even include rain as a fundamental component. The term, according to numerous dictionaries, means nothing more than a seasonal shifting of the wind. Thus, in India and Bangladesh, there is the “wet monsoon,” when the wind blows from the southwest between May and September, bringing with it quantities of tropical moisture that are inconceivable in the Rockies, and, to add a bit more confusion to the discussion, there is also the “dry monsoon,” when the wind shifts and blows in from the arid central Asian steppes.

According to experts, in its purest, historic context, the word “monsoon” likely ought never have left the Indian subcontinent and the other malaria-infested mudholes that make their way onto CNN every summer when entire villages are washed into snake-infested rivers as wide as lakes. But in the last couple centuries, it has indeed emigrated to points as far away as North America’s Mountain Time Zone, where it has found a nice summer home.

“There are a lot of terms that are used to describe the precipitation situation in the summer in the U.S., particularly in the Southwest and the southern Rockies,” Timothy Schott, a meteorologist with the National Weather Service Headquarters Office in Washington, D.C., once told me “People used to just call it the ‘rainy season.’ The term ‘monsoon’ gets thrown around quite loosely and, often, inaccurately. But we have started applying the monsoon concept to weather conditions in North America that mimic weather conditions in south and southwest Asia.”

Those conditions, according to Schott, consist of the seasonal shift of wind combined with a transference of moisture from tropical seas — in our case, the Gulf of Mexico and the Sea of Cortez — to otherwise relatively dry points inland.

“In the summer, global climatic circumstances result in low-pressure systems building up over Mexico’s Sierra Madre,” Schott said. “We see winds therefore rotating in from the south and southwest and picking up moisture in the Gulf of Mexico and the eastern Pacific. Because it’s summer, that air is warmer and, therefore, it can hold more moisture. It then carries that moisture as far north as the central Rockies.”

While there is still some barroom disputation among weather wonks regarding the correct application of monsoon terminology to the Rockies, that terminology has now reached official status as close as the Sonoran Desert of Arizona. Until the late-’70s, even weather experts were still debating what to call the summer precipitation systems that hit Arizona and New Mexico. As in Colorado, terms like “summer thunderstorm season” and “rainy season” were still being used in a very unscientific manner. It wasn’t until 2004 that scientists decided that the summer weather patterns that hit the Southwest, and, by extension, the Colorado mountains, were indeed “monsoons.”

And it wasn’t until 2008 that “monsoon season” was institutionalized by the National Weather Service the same way that “hurricane season” was institutionalized years ago. Now, “North American Monsoon Season” officially begins June 15 and runs through the end of September. The idea is that, by lending official nomenclature to the weather pattern, efforts to educate the public about monsoon-related dangers — flash floods, thunderstorms, lightning, rain-out company picnics — will be easier.

“People typically associate the term ‘monsoon’ with hot climates,” Jim Hall, a spokesperson with the National Weather Service’s Pueblo office, said. “Though the climate in the Colorado mountains is cold, the weather patterns that affect the area in the summer begin in the tropics. Colorado gets the lagging edge of those monsoonal weather patterns. So, it’s accurate to say that Colorado’s rainy season is a monsoon season.”

So there!

M. John Fayhee is the founding editor of the Roaring Fork Weekly Journal. He is the author of 10 books, including “The Colorado Mountain Companion,” from which this column is excerpted.