June 20, 2018 at 6:29 pm

OFFICIAL: Southwestern U.S. Monsoon To Start First to Second Week Of July; Impacts


The Southwestern U.S. Monsoon is expected to start during the first and second week of July, according to my latest numbers.  Read on more to find out what we are looking at across the region.

My latest numbers are showing a ridge of high pressure that will develop over the four corners of the Desert Southwest just after July 4th, with a static development by the 10th.  This would mean that the monsoonal flow (reverse winds from normal) will start in Arizona and New Mexico, including up through Utah and into Nevada as well.  This consistent clock-wise moisture is the power-house of the monsoon.  It grabs moisture from Mexico and swings it into the Southwestern United States, sometimes even here in Southern California.

There are times when hurricanes in the Eastern Pacific create a ‘kink’ in the ridge and thus an easterly wave is born.  Such a pattern is being seen around July 4th and afterwards and this is when I will start monitoring the moisture flow into Southern California as well.

There will be a number of strong Eastern Pacific Hurricane forming in the first and second week of July.  This will further amplify the monsoonal flow out of the southeast. We could end up with average to above average storms in the mountain/desert regions with a chance some of these easterly waves may bring activity east of the mountains into the adjacent valleys.

Regardless.. it’ll be hot and it will be be humid so if this affects you … you have your warning now.  Volcanic activity is ongoing in Hawaii.. but it remains at the surface.  We’ll need more So2 to get us cool again as we will close June at average temperatures inland, below at the coast, and slight above in our deserts.

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Things to note are as followed;

  1. Monsoon Season starts June 15th, however this year will be a mid-start, likely toward or in July.
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