The weather will be unsettled as we go through the weekend as a weak low pressure center off the California coast will work in step with a high at the Four-Corners region to steer up a wet southerly flow. Mainly afternoon thunderstorms will be scattered throughout the western part of Nevada and the Sierra. Temperatures will be seasonably warm through the weekend before cooling slightly and drying out early next week.

Monsoon Thunderstorm

Every once in a while you might hear me mention the monsoonal flow. When most people hear the term monsoon, they immediately assume that it means a heavy rain. And while rain can be a result of monsoonal flow, a monsoon is actually a wind.

monsoon-diagram

The term comes from the Arabic term “mawsim,” which means “season.” And it is a seasonal change of wind, classically recognized in India. During their summer, the effect of the extra heating on the massive landmass creates an onshore wind off the Indian Ocean, which results in their rainy season. So if that is the case, why can’t you call the rain a monsoon? It would be incorrect to call the rain itself a monsoon, since for every wet season the monsoon causes, it creates a dry one as well in the opposite season when the wind reverses itself.

Arizona Monsoon

Here in the southwestern part of the United Stated, we’ve adopted the term and apply it to the relatively persistent south wind we get around the Four-Corners High during the mid-summer months. It draws moist unstable air up out of Mexico across Arizona and sends it our way, and is one of the chief contributors to thunderstorm development. And while one might argue whether it is a true monsoon, since we really don’t get a seasonal reversal, the name has stuck.

 

 

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