Storm Postmortem: Friday’s southern Arizona severe weather outbreak

Late July & early August stands as the peak of the Monsoon. It’s a time of year when moisture and instability levels are at their highest, fueling severe weather outbreaks like the one that occurred Friday, July 29th.

The morning upper air data from Tucson showed the potential for a big day. See the red dashed line far away from the red solid line? That indicates the atmosphere has lots of energy (CAPE for the wx geeks). Ample moisture was also in play, along with a wind profile suggesting that cloud tops would trail storm cores. While mid level winds guided storms to the west, upper level winds at the tops of the storms  prevailed from the west-northwest.

Along with high pressure near the Great Basin, a dry line was present across southern Arizona. The biggest question was where the dry line would set up. That dry line ultimately wobbled east of Tucson by late afternoon, setting the stage for a major severe weather event.


Approaching the 5 PM hour, the Storm Prediction Center hoisted a Severe Thunderstorm Watch for Maricopa, Pinal, Pima and Santa Cruz Counties. The initial radar image show a few clusters of strong/severe storms that were moving to the west at 20-30 MPH.

That swift storm movement steered a line of severe storms into eastern Pima County in time for the evening rush. It wasn’t until 7:30 PM that Metro Tucson was free of any warnings or advisories. Thanks to the quick storm motion, there were little (if any) flooding issues.

What makes this event stand out is how long storms maintained their intensity as they tracked into the western deserts. While Tucson was calming down, a severe storm with the history of a haboob & 85 MPH winds swept through western Pima County around 10:30 PM. The wall of dust even made it into coastal areas of southern California!

July 29th Severe Weather Reports – Courtesy: SPC

When all was said & done, Arizona racked up a whopping 30 severe wind/hail reports. Gusts approached 90 MPH in Gila Bend and one area on Tucson’s northwest side recorded a 74 MPH wind gust. Many trees were downed around the Phoenix Valley. The bulk of the hail reports were concentrated in the southeastern metro around Vail & Corona de Tucson.

Storm chasers were all over these storms Friday. Here’s a few of my favorite shots sent in by our viewers.


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