Photographer Bryan Snider captured video of a remarkably beautiful microburst near Tucson on Saturday as scattered thunderstorms drifted across the desert terrain.
Around 11 seconds into the video, you can see the rain shaft grow larger and right in the middle of the frame, the microburst — slightly brighter than its surroundings — punches out of the storm toward the ground, and its wind spreads out in all directions.
In the second half of the video, Snider zooms in on the microburst and slows the video down. Here you can see the ball of rain and hail fall from the storm and crash into the ground.
Rarely do we get to see such a textbook visualization of a microburst — more often than not the microbursts we see in photos and video are obscured by rain shafts or occurring in densely populated areas. But the beautiful Tucson-area landscape was a phenomenal backdrop for this picturesque thunderstorm.
A microburst is a small downrush of rapidly sinking air occurring under the thunderstorm’s main downdraft. It’s usually located in the same region that the hail and heavy rain is falling from. In fact, it’s the load of the hail and heavy rain that drops from the storm, dragging the air with it and punching toward the ground.
“The fast descent of air is initiated by several processes – including the drag created by a large, sinking mass of rain water and hail,” says the Capital Weather Gang’s severe storm expert Jeff Halverson. “Additionally, evaporation of rain drops and melting of hail cool the air, increasing its density thus accelerating its descent. It is very common to observe wet microbursts embedded in pockets of heavy rain and hail.”
Once the microburst reaches the ground, the winds fan out in all directions, taking out trees, power lines and other structures as they blow quickly across the landscape.
Microbursts cause straightline winds that rival the intensity of a weak to moderate tornado, and have been documented with wind speeds up to 150 mph. However, their small size makes it inherently difficult to pick them out on radar, and thus they are nearly impossible to predict and warn for.
July and August are Tucson’s wettest months due to the North American Monsoon, a regional circulation that develops low pressure over the desert Southwest from July to September.