Monsoon season starting to look like a 'dud'

Aug. 15—Suffering through summer in the Valley without monsoon rains is like a kid getting birthday cake but no ice cream.

The 2023 season has been "a dud, so far, as the monsoon pattern has not set up for any period of time," said Paul Weser, a geography professor at Scottsdale Community College who did his doctorate on monsoons.

Even so, the Scottsdale Fire Department tweeted this week for drivers to stay alert:

"This monsoon season may not have many storms, but when we do get rain, it can be dangerous to be on the streets. Slow down on wet roads and please do not try to cross flooded washes."

While storms of the last two summers submerged some Scottsdale roads, this year's monsoon has been as dry as a James Bond martini.

Last month, Weser was hopeful that pressure systems would shift, as they often do at the end of July or beginning of August.

"They did not."

On Aug. 8, some parts of Scottsdale received a few splashes of rain. "We received about 0.04 inches here at SCC," Weser said.

That ended a long, dry stretch — but hardly turned on the rain taps.

A map by the National Weather Service compared this year's Valley weather to a three-decade average.

Weser pointed out the 30-year average shows a typical July has a high-pressure center over New Mexico, with the western portion over Arizona, "where it can transport moisture into the region from the south and southeast ....

"This would be our normal summer pattern that produces our monsoon thunderstorms during the season."

Weser noted this July's high pressure system "centered directly over Arizona ... thus there has been little opportunity to draw moisture into the state.

"We have instead been situated under the high pressure system, which is air sinking and heating as it moves toward the surface. This is what has caused our record temperatures and dry conditions."

According to the National Weather Service, prior to this year, Phoenix hit 119 five times: 122 (June 26, 1990); 121 (July 28, 1995); 120 (June 25, 1990); 119 (June 20, 2017); and another 119 (June 29, 2013).

This July, Phoenix hit 119 three times (July 18, 19 and 24), with an average high of 114.7 — 8.2 degrees hotter than normal.

While north Scottsdale can be as much as 5 degrees cooler than Sky Harbor Airport, the official location for National Weather Service Phoenix readings, parts of south Scottsdale are just as hot.

But there has been little relief from last month's scalding temperatures.

Though monsoon storms can form quickly, a few days ago Weser was not optimistic about typical August rainfall.

"Will we get the typical pattern to set up once and for all for any period of time? My guess would be unlikely at this point," Weser said, adding:

"Typically, by mid to end of August the pattern is starting to break down and on average totally gone by mid-September."

Weser said the Valley usually gets as much as half of its annual rain from mid-July through August.

"It's looking like we may not have as much as we had the last couple of years, which were really quite impressive," Weser said. "You may remember the last couple of years we had tremendous amounts of rainfall."

He cautioned that monsoon storms can be dangerous, particularly on occasions when "you have air coming from different directions and kind of collide ...

"And that's when we get a microburst."

Micro-moisture has been the story this August.

Though there wasn't much rain by the middle of last week, clouds at least helped cool down temperatures below 110.

This week, heat is likely to return.

"The high pressure shifts back over us for likely 110+ again next week," Weser said.

"What is happening is that we have some other smaller scale features in the atmosphere creeping in to prevent rain and pattern development. Kind of common as we get into August and the end of monsoon season."

There is still hope for rain fans around Scottsdale, however:

"What could still happen are surges of moisture from decaying tropical storms/hurricanes in the eastern Tropical Pacific," Weser said.

"September is a peak time for these storms and if the moisture gets tapped by the regional wind patterns it can flow up the Gulf of California and into Arizona."

He said these so-called "Gulf surges" can lead to impressive rain in September.

"These are not an annual feature of the monsoon," he added, "so no way to predict what will happen."