You may have heard or said something to this effect during heavy rain: "It's a monsoon out there!"
What is the monsoon?
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It turns out, though, that a monsoon isn't just a heavy rainstorm. It's a shift in seasonal winds, and it's something that's observed in several parts of the world.
This includes in the Desert Southwest of the United States, but also in places like "India, Spain, northern Australia and Africa except the Mediterranean," according to the American Meteorological Society.
How does the monsoon develop?
Similar to summer storms along the coast, it all comes down to wind shifts and temperature differences between ocean and land.
In this part of the world, it starts with converging air along the Sierra Madre Mountains, a major mountain range in Mexico.
In the late summer months, the land becomes warmer than the ocean.
This drives large pressure differences that alter the flow of air, such that it's directed from the ocean toward the land.
If you broaden out the view, you can see how the role of either the Pacific or the Gulf could play a major role in enhancing rainfall in states like Arizona, New Mexico, Nevada, Utah and Colorado.
Once the land cools more than the ocean, like it does in the winter, this monsoon shuts off and enters its dry phase.
How much rain caused the deadly flooding in the Grand Canyon?
Two people are reported dead following flooding near Phantom Ranch in the Grand Canyon. It happened August 29. Additional flooding was observed at Zion National Park two days later.
When you look at the estimated rainfall totals in each of these locations, you see they received an inch of rain or more.
That doesn't seem like much to us in North Carolina, but it is to places that see that as their monthly average in the month of August.
Couple that with drastic changes in elevation, and you have a recipe for flash flooding. This flooding is common in the side canyons of the Grand Canyon during these monsoonal shifts.
So while what happened recently is not uncommon, it's incredibly unfortunate because it happened in one of the most popular spots of the Canyon.
Could El Niño enhance the monsoon?
El Niño could certainly enhance the monsoon.
We recently covered what El Niño could imply locally in the coming months.
El Niño refers to the warmer-than-average waters along the Equatorial Pacific. Warmer air carries more water vapor.
So as this monsoon shift occurs, more moisture is being directed toward the Desert Southwest. This means there's at least the potential for more heavy rain and flooding episodes in that part of the country.