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Location and elevation often put the southern Arizona city in the eye of the storm.
It seems Tucson is the favorite target in the Southwest of thunderstorms, floods and other extreme weather events.
That’s not the punchline of some joke originating out of Tempe attempting to gin up a state university rivalry. It’s the conclusion of a University of Arizona study about the economic impacts of extreme weather.
Tucson sees the highest frequency of storms and suffers from the damage those events cause more so than other Southwestern cities such as Austin, Las Vegas, Phoenix and San Diego. The study was conducted by a pair of researchers at the UA’s School of Government and Public Policy. It concludes that while Tucson was hit most frequently, the impact of those weather-related events (including wildfires) statewide has cost Arizona $3 billion since 2010.
Authors Laura Bakkensen and Riana Johnson examined the period from 1996 to 2016, covering 12 cities in eight Western states.
It determined the Tucson region gets hit with about 47 extreme events, leading to one death and three injuries annually. That includes wildfires and the occasional winter storm.
This isn’t happening because the city is cursed — it’s the result of Tucson’s location, elevation and the monsoon.
The Mount Lemmon effect
State Climatologist Nancy Selover explains.
“Mount Lemmon is a sky island,” she said. “Basically, it’s this huge thing that sticks up in the landscape. This very sudden change in elevation that is Mount Lemmon means it is the starting place for a lot of thunderstorms in the summer time. They basically form right over Mt. Lemmon.”
Warm moisture during monsoon conditions cools, and the moisture condenses as it rises up the mountain.
“If you go down in the summer and basically watch Mount Lemmon, you’ll see these clouds form and evaporate and grow and evaporate,” Selover said. “Pretty soon in the afternoon they have enough moisture that has gone up the mountain that they just explode.”
Those storms sometimes result in flooding, hail and destructive outcomes. Although Tucson generally has mild winters, there is an occasional winter storm.
“The flooding is quite severe also because they have the steep terrain and washes that drain the mountains running through the city,” Selover said. “In winter, when storms track that far south, their elevation enhances the chance of snow and freezing. Phoenix’s elevation is pretty low, so when we get any snow in winter, it’s usually only a light dusting which falls mainly at Carefree and our higher elevations.”
Of the weather events recorded:
- The Tucson region has the greatest number at 995.
- San Diego follows with 973.
- Colorado Springs has 871.
- The Portland region had the fewest extreme weather events, at about 83.
What about Phoenix?
Tucson’s numbers were driven by storms during the monsoon, according to UA Climatologist Mike Crimmins. Phoenix just doesn’t get the same amount of storms.
“I think it’s a frequency game at this point,” he said. “(Tucson) probably gets a third to half as many more storms. If you look at the total precipitation during the monsoon season between Phoenix and Tucson, I think we get more than twice as much. Phoenix would get more in the way of dust because of the outflows and those kind of things.”
Among cities included in the study:
- Tucson leads all cities in monsoon rain with 6.08 inches on average.
- El Paso is next with 5.14 inches.
- Albuquerque follows with 4.61 inches.
- Phoenix averages 2.71 inches of rain during the season.
(The National Weather Service defines the “Arizona monsoon season” as June 15 through Sept. 30.)
Other cities included in the study, such as San Diego and Portland, see more rain on average, but it doesn’t usually come from brief, intense storms that cause flooding.
“San Diego gets just about all of its precipitation during the winter,” Crimmins said. “It’s going to be those longer-duration, lower-intensity type rain systems. They do get those atmospheric river, El Niño-fueled intense storms, but not every year. Portland is even more quiet. They get a lot of rain, but it’s day-after-day light rain, so it doesn’t cause any trouble.”
Call for action
The authors of the study hope its findings will drive home the importance of getting information about extreme weather events to the public before and during the storms.
Getting information to the public also can be crucial during rare weather hazards, such as winter storms. Bakkensen and Johnson found that even though winter storms don’t happen often in Tucson, they account for about 10 percent of storm-related deaths in the area during the study period.
They held up programs such as the Arizona Department of Transportation’s “Pull aside, stay alive” campaign to highlight how drivers should respond to being caught in dust storms as examples of successful information efforts.
“While information does not reduce damages directly, it allows for better decision making that will reduce destruction and save lives, often at low cost,” Bakkensen wrote. “Staying up to the minute on information can help you stay safe, especially during the monsoon.”
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