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Weather Wise: The Missing Monsoon

Weather Wise: The Missing Monsoon
Posted at 5:07 PM, Jul 10, 2023

People sometimes associate heavy, seasonal rain when they hear the term monsoon but that's not exactly accurate.

The North American Monsoon is a seasonal change in atmospheric circulation that occurs as the summer sun heats the continental landmass.

During much of the year, the prevailing wind over the southwest is from the west and dry. As summer heat builds over the west, a region of high-pressure forms near the four corners and the wind becomes more easterly or southerly, bringing moisture into the deserts. This monsoon moisture usually lowers the wildfire danger in Arizona, Colorado, Utah and New Mexico in the middle of summer.

The monsoon high often impacts Montana, just in a different way. The position of the high over the four corners region puts Montana in a southwest flow, producing more heat than anything else. Isolated thunderstorms usually are moisture-starved, resulting in more dry thunderstorms, raising the wildfire danger.

Currently, the North American Monsoon has not developed yet. The southwest has been very hot and dry with excessive heat warnings. In Montana, temperatures have been moderate with a wet pattern of thunderstorms producing heavy rain.

However, although late, the monsoon shift appears likely to develop with seasonal changes in different regions.