Phoenix microbursts cause tornado-like damage

The Phoenix monsoon season is in full swing, which means tiny but violent weather phenomena called microbursts are wreaking havoc across the Valley.

Why it matters: Wind speeds can top 100 miles per hour during these events and produce damage similar to that of a weak tornado, National Weather Service meteorologist Tom Frieders told Axios.

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• A Phoenix man died when a microburst caused a warehouse roof to collapse in July, and they frequently down trees and power lines.

How it works: When thunderstorms form on hot, dry days , sometimes raindrops evaporate as they reach the lower level of the atmosphere, cooling the air around them, Frieders said.

• Because cool air is denser than the warm air, it accelerates toward the ground at a high speed, bringing sudden and sometimes violent wind with it.

The intrigue: It's not unusual for a microburst to hit somewhere in the Valley on any given day of the monsoon season, but they typically impact a very small area — a couple of square miles at most, per Frieders.

• The storms that accompany a microburst can pass in less than a half hour, he said.

The microburst uprooted this mesquite tree and broke a water pipe. Photo: Jessica Boehm/Axios

Zoom in: A microburst ripped dozens of mesquite and palo verde trees out of the earth last week in Ahwatukee.

Thought bubble: The storm came on quickly — and left even faster. There was no hint of rain when I went into the gym, and an hour later, the only sign it had passed through was 10 downed trees in the parking lot, including some that landed on parked cars.

The bottom line: Pay attention to the daily forecast and avoid outdoor activity if storms are expected, Frieders said.

• If you find yourself in the middle of a microburst, get indoors immediately and stay away from windows (they've been known to shatter in high winds).
• And, as some of my fellow gym-goers learned the hard way last week, don't park near trees if there's a chance of storms.

There were at least 10 trees downed in this Ahwatukee parking lot. Photo: Jessica Boehm/Axios