Monsoon Classroom: The Four Corners High

What drives the Arizona Monsoon? The blog’s “Monsoon Classroom” breaks down the 5 main patterns that help fire up our Summer storm season.

Courtesy: NWS Tucson
Courtesy: NWS Tucson

In short, the Four Corners high is the most common pattern during the Monsoon. High pressure resides near the Four Corners region, allowing winds aloft to shift to the east or southeast. It’s this wind shift that defines what the Monsoon truly is: a seasonal wind pattern, not an individual storm.

Why is this wind shift so vital? Southeasterly winds tap into moisture sources like the Sierra Madres and Gulf of Mexico. Add daytime heating and rising air over the mountains and you get the recipe for our daily rounds of thunder.

Courtesy: Mike Olbinski

The Four Corners high can also produce severe weather. Case in point: July 5th, 2011. A series of severe thunderstorms walloped Metro Tucson, producing 70 MPH wind gusts. These winds also developed a massive haboob that engulfed the Phoenix Valley. The dust was so dense, Sky Harbor Airport was shut down for almost an hour.


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