From a trickle of water running between rocks in a dry, arid mountainous landscape to a roaring river in a matter of minutes: monsoon flooding in the southwest is increasing rapidly. Every summer, extreme meteorologist Reed Timmer, who can be best known for chasing tornadoesit continues with “flash flood chases” in which he aims to capture the moment when rainwater transforms the parched landscape into a dangerous wall of water.
A dramatic video recently captured by Timmer perfectly illustrated the North American monsoon which was in full swing at the beginning of August in Wilhoit, Arizona, a city north of Phoenix. The rushing water quickly created a roaring river in the desert landscape of Arizona.
Watching Timmer perform these “flash flood interceptions,” as he describes them, is something to marvel at and many who watch these videos may end up wondering: How did he do that?
“I’ve always been interested in small-scale meteorology, including tornadoes, lake-effect snow and flash floods, but I love the hybrid atmospheric and geographic approach to chasing flash floods,” Timmer told AccuWeather in an interview. “It also requires all of your senses: you can often hear the flash flood approaching several minutes before it hits.”
In the Southwest, states like Arizona and New Mexico are typically arid for most of the year and rely heavily on the monsoon season for annual precipitation. AccuWeather explained meteorologist Alex DaSilva.
The dry, hard, cracked earth and sparse amount of vegetation in the Southwest make it almost impossible for the ground to absorb water, often resulting in runoff when it rains. And it only takes an inch or two of rain to create a life-threatening situation.
“Flash flooding can happen very quickly. Since the Southwest doesn’t typically get as much rain as eastern areas, it only takes a small amount of rain to cause a flash flood,” DaSilva said.
Timmer captured the moment that people rarely see last week. Arroyos, or dry creek beds, in the area quickly filled with a surge of water that seems to have no end in sight.
Water running down a creek in Wilhoit, Arizona. (Extreme Meteorologist Reed Timmer)
As water flows through the newly formed riverbed, which was created in a matter of seconds in front of Timmer’s camera, the front wall of a flash flood forms.
These creeks and slotted canyons carry this fast-moving water several miles from where the storm occurred, which can affect areas where it hasn’t rained and threaten hikers who don’t know the weather.
“I use radar-derived rainfall data and target storms that even have a little bit of shift evident in radar reflectivity,” Timmer explained. “This means they’re producing a lot of rain and they’re releasing the thermal energy stored in the water molecules, which causes the storms to have a little twist.”
Timmer explained to AccuWeather in 2018 when he started chasing floods in the Southwest, as water flowed through streams, debris came with it, which he describes as a “debris plug.”
According to Timmer, when streams haven’t flooded in a while, they usually have a huge plug of debris. Due to ground friction, the debris plug moves more slowly, allowing the flood to build up behind the plug.
“I also focus on old burn-scarred areas from previous wildfires, because they can flood much more easily and often have debris flows or debris plugs along the front wall of the flood,” Timmer said. . “The debris gives the flash flood even more destructive power.”
In a video he captured in 2018, the A plug of debris can be seen holding back a powerful stream of water.. The videos of him are just another reminder not to underestimate the power of fast-moving water. An afternoon outdoors or a hike in the canyons can quickly turn into a life-threatening situation.
“It’s about patience and waiting for the flood to come,” Timmer said. “The land surface here in the desert southwest doesn’t absorb water very quickly, especially through burn scars, so it only takes about 0.75″ of rain per hour to produce a flash flood that life threatening.”
According to the National Metereological Service (NWS), more people die annually as a result of floods than from hurricanes, tornadoes and lightning, and although flash floods are a specific type of flooding, they still cause a significant number of victims each year.
Earlier this month, heavy rains caused deadly overnight flash flooding in eastern kentuckyresulting in more than 38 victims.
AccuWeather forecasters say these elusive videos illustrate how dangerous flash flooding can be and highlight the importance of paying attention to everyone weather warnings and evacuation orders.
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