A1 Communications Cable Techs Health Care Sierra Tucson Eating Disorders Program Coordinator Trades/Construction RANCHO RESORT MAINTANANCE POSITION Tucson RegionUnofficially, it was a wet monsoonARIZONA DAILY STAR
Tucson, Arizona | Published: 09.28.2008
Disregard the average rainfall readings at the airport this summer.
It was wet.
You know it. I know it. Your crosstown buddy, who always brags that he got more rain than you did, knows it.
This was a good year for the North American Monsoon in Tucson, with double the normal precipitation in many parts of town.
Above-average rainfall was recorded at nearly 90 percent of 127 rain gauges in the Tucson metro area maintained by Pima County or the citizen scientists in the University of Arizona's RainLog program.
There were two dry patches: in the vicinity of Marana and Avra Valley, and in the area right around Tucson International Airport, where the official measurement is taken.
Elsewhere, we got socked. Rain fell in buckets on a couple of occasions, leading to double the normal totals in parts of Midtown Tucson, Green Valley, Vail, and the Sabino and Bear Canyon areas.
Monsoon season, which began June 15, will officially end on Tuesday. A slightly below-average official total of 5.82 inches had been collected at the official National Weather Service rain gauge at Tucson International Airport by Friday.
But the climate geeks are convinced that this season was well above average, and the unofficial data seem to support them.
Combining results of the 50 automatic tipping gauges operated by Pima County with those maintained by 77 citizen weather watchers of RainLog.org produces a much damper than normal picture.
"Ninety percent are above 6 inches, and most are significantly above," said Gary Woodard of the Center for Sustainability of semi-Arid Hydrology and Riparian Areas, RainLog's coordinator.
"Officially, we're average," said Mike Crimmins, climate specialist with the UA's Cooperative Extension and Woodard's partner in RainLog. "But most parts of town got a lot more rain than the airport, and the airport was just one good storm shy of producing a better result," Crimmins added.
More than 60 percent of the sites recorded precipitation at least 33 percent above normal levels.
It's not necessarily a case of having the official rain gauge in the wrong spot, said Chris Castro, a UA assistant professor of atmospheric sciences. Castro used four forecasting models to predict an early and wet monsoon back in April.
"I would seriously doubt over time you would find areas wet or dry. It's just the hit-or-miss nature of thunderstorms," he said.
He pointed to Sierra Vista, which when we spoke two weeks ago had received less than 7 inches, while just down the road, the Coronado National Memorial collected twice its annual average — nearly 17 inches of rain.
The only predictable variance, Crimmins said, is caused by elevation. The higher you go, the more rain you get from the North American Monsoon.
Of 127 readings on the RainLog map, the lowest total — 2.83 inches — was recorded at the lowest site, near the Santa Cruz River in Marana. The highest — 20.43 inches — was collected in the highest gauge, near the Palisades Ranger Station on Mount Lemmon.
Totals are also predictably high in the mountain foothills.
But many low-lying areas of town got drenched by multiple storms last summer. Some Midtown loggers collected 12 inches of rain or more.
Big storms, some fueled by moisture surges from tropical storms in the Gulf of California, produced daily totals of up to 3 inches. A July 10 storm dropped 2.65 to 3.0 inches in northeast Tucson. Green Valley recorded 2.7 inches on July 19, and the West Side was hit by a 2.8-inch storm on Aug. 31.
Of course, on those same days, you may have been totally dry at your home.
That's due to the unique nature of thunderstorm production in the mountainous desert.
The easterly wind that triggers a "monsoon" shift in our weather patterns doesn't bring storms into the area. It brings moisture. Thunderstorms are produced locally as our mountains become cloud factories. Our relentless summer sun heats the east-facing flanks of our mountains each morning, triggering a convective current that pushes moist air into the upper atmosphere, where it cools and condenses.
Then those clouds blow over town in late afternoon, or away from town, releasing rain in random blessings, triggering bouts of monsoon envy.
"It's that classic monsoon phenomenon," Crimmins said. "If it rained where you're at, things look good."
Crimmins said he did "OK" at his home near Camino Seco and Broadway. "But there were a couple of days when I was so jealous of you guys in Midtown. I'd get a half-inch; you'd get 2.
"That's just how thunderstorms work here in the Southwest," he said. "They put down huge amounts of rainfall in very small areas. They very quickly blow up, morph and die."
The official total for this monsoon will be average, said meteorologist Erik Pytlak of the National Weather Service, but "it was wet — parts of the city were quite wet."
All the ingredients for a good monsoon were in place most of the summer, Pytlak said. The high pressure migrated northward early, setting up the easterly flow. In addition, a series of tropical storms off Baja California kept the air quite moist, he said.
On most days last summer, the air was sopping. If it didn't rain at your house, well, maybe you should move farther away from the airport.
● Contact reporter Tom Beal at 573-4158 or tbeal@azstarnet.com.
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