Prescott still waiting for its big monsoon rain
PRESCOTT – Northern Arizona's monsoon arrived at the start of this month, but Prescott still is waiting for its first major storm.
That's typical for the monsoon, noted Tyree Wilde, National Weather Service meteorologist in Flagstaff. Rains are spotty; one area could get drenched while another site a few miles away gets nothing.
So far this month, Prescott's official Sundog measuring site on the northeast side of town has recorded only 0.02 inches of rain, on July 3.
Yet, northern Yavapai County was getting soaked Tuesday, and Flagstaff received 1.2 inches Monday. Areas closer to Prescott haven't seen that much, but they've seen a heck of a lot more than Prescott: Chino Valley, 0.28 inches on Monday; Prescott Valley, 0.10 inches on Thursday and Monday; and the Prescott National Forest near Prescott, 0.26 inches on Thursday.
Prescott may get its chance by Friday, since the forecast calls for mostly or partly cloudy skies each day with a chance for thunderstorms.
The word monsoon comes from the Arabic word mausim, which means season.
The monsoon in Arizona marks a seasonal wind shift, when the winds start coming from the south instead of the west.
This northward movement of a huge, upper-level subtropical high-pressure system, called the Bermuda High, allows moisture from the Gulf of California and Gulf of Mexico to stream into Arizona.
The season typically begins in the first half of July in the Prescott area, then ends in the first half of September. Last year, it arrived in Prescott June 18, the earliest date since the Weather Service started labeling the season in the 1950s.
The Weather Service expects a drying trend to set in throughout northern Arizona this weekend, Wilde said.
That's typical for the monsoon, too; it's called a break, when the southerly winds decrease for a few days or even a week.
The other half of the monsoon pattern is called a burst, when weak disturbances in the upper atmosphere focus thunderstorm activity over Arizona for a few days to more than a week.
The 102-year average precipitation for Prescott is highest in August, at 3.32 inches. July comes in second with a 2.94-inch average. September, with a 1.74-inch average, is similar to the months of December through March.
June typically is Prescott's driest month, with a 0.41-inch average.
Last month was drier than average, with precipitation totaling 0.11 inches at the Sundog site, and above-average temperatures.
Contact Joanna Dodder at firstname.lastname@example.org