MONSOON REPORT CARD

Rainfall was just average - but hey, we'll take it

2012-09-30T00:00:00Z 2014-07-22T16:52:16Z Rainfall was just average - but hey, we'll take itTom Beal Arizona Daily Star Arizona Daily Star
September 30, 2012 12:00 am  • 

This summer's monsoon seemed like a return to the good old days, even though rain totals were simply average throughout most of the Tucson region.

We were dripping with the possibility of thunderstorms on most days from the end of June until mid-September.

"It was the kind of monsoon long-time Tucson residents describe, where the clouds roll in every day at 4 p.m. You could set your clock by it," said Gregg Garfin, climatologist at the University of Arizona.

The dew point readings - the temperatures at which moisture condenses into rain - tell part of the tale. From June 25 to Sept. 13, there were only 13 days in which the dew point fell below 54, the traditional measure of possible rain. For much of July and during the end of August and beginning of September, those readings were in the upper 60s. The amount of "precipitatable moisture" was huge and just waiting for conditions favorable to thunderstorm formation.

In July, everything clicked, delivering slightly lower temperatures, great lightning displays and 4.13 inches of rain - well above the normal 2.25 inches.

"July Fourth stands out, up in Oro Valley, with about 3 inches of rain in an hour," said National Weather Service meteorologist John Glueck.

In mid-July, Glueck said, it rained for three days straight. "It was a good start to the monsoon, then it petered out a little bit in August."

August and September combined for only 1.55 inches, well under the normal 3.68. Temperatures were slightly above normal.

The end result was a normal monsoon in both temperature and precipitation - 6.02 inches of rain at the official weather service site at Tucson International Airport, compared with the normal 6.08 for the period running from June 15 to Sept. 30.

As always, the precipitation was not evenly distributed.

"Some places got dumped on," said Michael Crimmins, UA climate scientist and extension specialist.

"The frequency of precipitation was really pretty high, relative to the last couple years," he said.

Crimmins said his east-side home was hit by only one downpour with about an inch of rain, but another dozen rainstorms delivered lesser totals.

Tucson was a dividing line for precipitation, said Crimmins. To the west, it was wetter; to the east, drier.

"The Tohono O'odham had an epic monsoon," said Crimmins.

Summer rains of 9 inches or more were common in the vicinity of Tucson Mountain Park and northwest of Tucson, according to Rainlog.org, the citizen-science program run by the UA College of Science.

Rainlog director Gary Woodard said he was surprised, in looking at more than 2,000 Arizona monsoon readings, to find the totals were merely average throughout most of Tucson. It had seemed like such a good monsoon, he said. "It had high-entertainment value, but just average precipitation."

The mountains, as usual, snared copious moisture. The higher reaches of the Santa Catalina Mountains received 10 to 21 inches of rain, according to gauges operated by the Pima County Flood Control District.

Elsewhere in Arizona, summer rain was heavy enough to provide at least short-term relief from drought conditions. "The area classified with severe or extreme drought fell from 93 percent in mid-August to 32 percent in mid-September," according to CLIMAS, the UA's climate assessment report.

The entire state remains in some stage of moderate to extreme drought, however.

"In far southeastern Arizona and western New Mexico, they're in real trouble," said Crimmins.

The monsoon came late and gave little to western New Mexico, where higher temperatures and sparse rain contributed to a record wildfire season.

Winter rain is the crucial ingredient for long-term relief, according to the U.S. Drought Monitor.

"We need multiple seasons of average to above-average precipitation to knock back the drought conditions," said Crimmins.

"Some places got dumped on. The frequency of precipitation was really pretty high, relative to the last couple years."

Michael Crimmins, UA climate scientist and extension specialist

Contact reporter Tom Beal at tbeal@azstarnet or 573-4158.

Copyright 2014 Arizona Daily Star. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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