Some desert wind comes down, not across. A microburst is a concentrated column of air that plunges out of a thunderstorm, hits the ground, and blasts outward in every direction, a brief and violent burst of straight-line wind that can reach around 60 miles an hour and is gone in a few minutes. A downburst under two and a half miles wide where it lands is a microburst; larger than that and it is called a macroburst.
Evaporation is the engine. In a monsoon storm, rain falls into dry air and evaporates, which cools the air it falls through; the chilled air is denser than its surroundings, so instead of drifting down it accelerates, plunging as a fast column toward the ground. When that column hits, it has nowhere left to go but sideways, so it spreads as a radial slam of wind, a rain-and-dust foot flaring out from the point of impact.
The shape it leaves is the tell. A steady gale pushes everything one way, but a microburst fans out from a center, so the scrub and small trees near where it struck are pushed flat in a starburst, all leaning away from one point rather than all leaning the same direction. On bare desert ground it throws its own radial ring of dust.
It is also the engine behind the bigger dust events. The outward blast of a microburst is exactly the kind of gust front that lifts a wall of dust into a haboob, and a microburst over dry ground is a fast, local, violent thing in its own right, brief enough to miss if you blink and strong enough to take down a carport.
Do not confuse it with a tornado. A tornado draws air in and up in a tight rotation; a microburst does the opposite, driving air down and out with no spin at all. And do not confuse it with a dust devil, which is a small fair-weather vortex that needs no storm. The microburst needs a thunderhead above it.
A dark shaft slamming straight down under a storm and flaring wide at the base is the wind coming for the ground.