PHOENIX — Editor's note: The above video was the forecast on May 18.
The daily storms this week have brought up the question: Is this an early start to Monsoon 2023? Are we having a “May-soon”?
The short answer is no.
Our monsoon season officially begins on June 15 and runs through Sept. 30.
Although not every rain event during the monsoon follows the perfect monsoon setup, our current weather pattern doesn’t follow the typical monsoonal pattern either.
The monsoon season is marked by a wind shift.
During a monsoonal pattern, winds typically blow from the south and southeast and draw moisture in from the Gulf of California and the Gulf of Mexico. As a result, humidity levels will rise and storm chances will become more prevalent.
The typical summer setup is marked by a thermal low off the Baja Peninsula and an area of high pressure near the Four Corners. Counterclockwise flow around the low and clockwise flow around the high generate those southeasterly winds, which leads to more humidity and higher storm chances.
This week, our weather pattern has been different. Even though we have more moisture in our atmosphere than what is typical for May, the storms are not the result of an early start to the monsoon season.
Right now, there is an area of low pressure over southern California which is further north than what is typical over the summer. Moreover, the high is over AZ instead of the Four Corners. As a result, the primary wind direction this week is from the west and southwest.
The location of that thermal low is very important for drawing in more humidity and southeasterly winds. June is typically the hottest and driest month of the year in Phoenix! We need those 110+ degree days to get that thermal low in its proper placement over the Baja to generate monsoonal flow. This is why we need the high heat to kick off the monsoon season before the humidity rises in July and our average first stormy weather of the monsoon is in July.
This week has featured some similarities to the monsoon, such as blowing dust and slow-moving storms, but the setup to what got us there is different than to what is typical over the summer months.
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