A late start to monsoon storms looks likely

Published: May. 31, 2011 at 12:43 AM MST|Updated: Jul. 11, 2011 at 2:02 PM MST
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Southern Arizonans may enjoy the cool temperature swings this spring each week. But there are consequences for putting off the sizzling heat.

We've seen a repeat pattern of warming up, followed by windy transitions to below-normal weather. As that pattern continues, the affect it will likely have on the Monsoon's start is unwelcome news to an already parched southern Arizona.

With the jet stream (steering wheel for storms) still located roughly through northern California, wind from the west has been stopping any significant permanently-placed ridge of high pressure from forming over the Southwest. This high, which eventually centers itself over the 4-Corners region, is essential for entrenchment of a Monsoon flow of air from Mexico into Arizona.

The current pattern looks to repeat itself, with west-to-east wind blowing through Arizona, through at least mid June.This will act to push dry air into Arizona and prevent the pre-Monsoon pattern from forming.

What does it all mean? Southern Arizona is likely to see a late start to Monsoon storms.

Southern Arizona usually sees its first Monsoon storms around July 4th. So, it's certainly not too late for this pattern to change. However, patterns that are this repetitive in the atmosphere through the entirety of spring almost always continue into the summer. If this holds true, our Monsoon storms will arrive late, perhaps not occurring on a regular basis until well after Independence Day.