Monsoon 101: Mogollon Rim Storms - Tucson News Now

Monsoon 101: Mogollon Rim Storms

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When storms from the Mogollon Rim aim toward Tucson, they frequently bring with them damaging wind.

Unlike a "typical" Monsoon day, where storms are moving very slowly, when the "Mogollon Rim" pattern sets up, the storms move rapidly. That rapid motion translates into strong, sometimes damaging, straight-line wind.

The Mogollon Rim runs from eastern to north-central Arizona, and is the beginning of the Colorado Plateau. It juts above the rest of Arizona, starting at a 7,000 feet elevation.

When Monsoon moisture flows north from the tropics, the moisture-rich air hits the Rim. This forces the humid air upward, cooling it and condensing the water vapor (humidity) into visible cloud particles and eventually thunderstorms with wind and heavy rain.

When an upper-level area of high pressure is positioned northwest of Arizona, the flow around it controls the direction of movement of clouds and storms. The clockwise flow pushes thunderstorms that form along the Rim toward Tucson.

These individual cells usually die off before they hit the valley locations, but the colder rain cooled air associated with the storms roll under the hot valley locations. This affect allows the hot moist air to rise and new storms are formed in the desert floors.

A BRIEF DESCRIPTION FOR SCREEN READERS
The Mogollon Rim 
Typical moisture flow during Monsoon
Air hits the Rim and pushes up
Storms form due to rising air
Rainfalls at Rim and produces cold air and pushes down to deserts
That cold air pushes the hot desert air upward and storms form over the deserts

 

 

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