Monsoon’s a Brewing: Beauty and the Beast

Thursday, July 2nd, 2015

cloud1By Aimee Snyder, MPH

The humidity builds. Clouds roll, thicken and darken. A cool breeze brings the smell of creosote, a telltale sign that rain is near.

The Sonoran Desert is particularly alluring during monsoon season. The extreme summer heat and sunshine are tempered by sporadic overcast skies and rains – allowing the outdoor – loving desert dwellers a brief chance to catch a rare moist and fragrant mid-morning or afternoon run, bike ride or hike. It is a beautiful and important time of year for replenishing the deserts water stores, but the cocktail can be a deadly beast of her own.

Monsoons in southern Arizona are caused by the rising hot air over the desert and the cooler Pacific Ocean air rushing in to fill the vacuum, according to The University of Arizona Climate Assessment for the Southwest called CLIMAS. Monsoons, from an Arabic word meaning season, happen similarly in other parts of the globe with geographical features like Tucson’s, according to the National Weather Service. The cool air warms from the heat of the desert land, causing thunderstorms and rains. Cooler air atop the warming air sinks, warms and further aids the thunderstorm production, and creates another vacuum higher in the atmosphere to draw more cool Pacific air. It is a tango between cool oceanic air and hot desert air, dancing within the high mountains that surround the Tucson basin.

A Harrowing Tale of Monsoon

It was a couple weeks into monsoon when four day hikers set out to find Seven Falls, part of Sabino Canyon Recreational Area in Tucson. The hike was on the heels of a particularly stormy day the previous week. The falls were sure to be running.

Seven Falls is on the Bear Canyon Trail, 2.5 miles from the trail head, 4.5 total miles from the parking area. Its name portrays its structure: seven cascading waterfalls streaming down from the Catalina Mountains, having chiseled the granite rock over time.

Two of us had attempted the hike months prior, but the waterfalls were dry with a few stagnant pools of water. The sun and heat had chased us out of the chasm, dehydrated and sunburnt.

When the rains and cooler temperatures came, we thought this was a better time to revisit Seven Falls. As transplants to the desert and beginning hikers, we were not aware of the dangers of hiking in a canyon during monsoon.

We had checked the weather before we left the house at 6 a.m. (30 percent chance of rain). We set out with a plan to turn around or climb to higher ground should the sky turn ominous or the water rise. Neither happened. The sky was overcast and there were no warning signs of the torrential downpour we never knew happened and the subsequent flash flood that changed many lives.

That morning (Aug. 4, 2007) the desert was alive and active after the cooling mid-week rains. We saw a Gila Monster, a desert tortoise and a plethora of lizards before even reaching the trailhead. A rattlesnake coiled just off the path, sounding his alarm. A rich red cardinal kept watch from the reach of a mesquite tree. The river flowed, but not so much that upwards of 50 hikers could make the many river crossings safely by jumping from rock to rock.

We were amongst many others at Seven Falls when the dark, violent water thundered over the 3rd waterfall. We had not felt a drop of rain, saw no black clouds, nor heard a clap of thunder in Bear Canyon; however, we learned later that a sudden super storm had formed miles upstream on Mt. Lemmon. It had raged on for an hour causing a 10-foot surge in the river, carrying the debris flow that contributed to the thunderous sound. This thunderous sound of the water raging down the narrow canyon and waterfalls was the only warning for those along the canyon – a warning that came too late for our two hiking companions.

Sitting on the slide rock at the base of the tall waterfall, the first edge of the 10-foot wall of water squeezed through the narrow canyon and came down with a splash and noticeable drop in temperature. That first splash swept my friend Angela Knoche, 19, off the slide rock where she had been dangling her feet into the water. In seconds, Knoche was downriver, reaching her hands out to Tim Hahn, 25. Hahn had lunged to grab her hands in time, but the swift water proved too powerful pulling Knoche out of Hahn’s grasp, yanking Hahn into the flood. Neither survived. Many hearts were broken: ours, wrenched in guilt.

Monsoon Safety: “Turn Around, Don’t Drown”

Though the stormy season provides a relief from the obvious dangers of extreme heat and sun, monsoon brings a few risks of its own: microbursts of air causing intense wind gusts and blowing dust clouds called haboobs, lightning and wildfires, and, as illustrated above, deadly flash floods. Flash floods are the number one weather-related cause of death in the country, according to a Monsoon Safety brochure published by Pima County Regional Flood Control District. It is important to note that flash floods can appear miles from a monsoon storm with no warning signs.

The monsoon period for Arizona is June 15 through September 30th, according to CLIMAS. We are in the heart of it right now.

Tips for Monsoon Safety:

1. Sign up for severe weather notifications, such as text message alerts from Tucson News Now. Make a personal policy to stay safely indoors when warnings are issued. Check for watches prior to outdoor activities in a flood-prone area such as hiking, biking, or running in canyons or low-level run-off areas like Agua Caliente Wash.

2. Visit the National Weather Service’s Tucson Monsoon Information to learn more about the unpredictable forces of the season. Also available are interactive weather and hazard maps for the local area, including the mountains and canyons.

3. View a floodplain map for the areas you live, drive through, and recreate. Pima County Regional Flood Control District’s website houses an interactive map function for finding the flood plains near any address within an incorporated Pima County as well as provides a Monsoon Safety brochure with a list of flooding crossroads.

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