Summary of Yesterday Afternoon's Storms

Yesterday was the second storm event this summer that occurred during a strong downslope wind event, associated with a backdoor cold front. Events like this are usually the kiss of death for rainfall in the Tucson metro area - but we've had two this year, so this is quite unusual!

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The airport had a severe thunderstorm just before 4 pm with gusts to 69 mph and 0.61" of rain. The Atmo rooftop anemometer had a gust to 78 mph from the south an hour or so later, but no rainfall - dust and debris with that outflow. There were several other reports of strong winds and trees down in the area around Davis Monthan AFB. Here at house we had some gusty winds, but only of about 35 mph or so, with lightning and thunder but just a few short bursts of rain - total here only 0.02".

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The Rillito Wash had flow during the night that must have come in mostly from Alamo Wash, which drains the east central part of town. The storms yesterday mostly avoided high-elevations and struck in low elevation areas - again, another unusual aspect of the event.

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Across the ALERT network, 21 of 93 gauges (about 22%) had measured rainfall during the 6-hours ending at 6 pm last evening. No additional sites had rainfall after 6 pm. Six sites had over half an inch of rain and Summit Elementary reported an inch and a half. A gauge at Alamo Wash and Dodge had nearly an inch.

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Images above are: Top - photo from the house of the storm near Alamo Wash and Glenn, view is looking a bit south of east. The cell that later struck the airport developed off to the south (right) of this storm. Middle - during the few bursts of rain here at house the drops were large and there was full sunshine. The drops were sparkling like gemstones as they fell, and I tried to get a photo. Didn't come out well, but if you look closely at the photo there are some captured that look like minature white comets. Bottom - radar rainfal estimate from Tucson radar for the period ending at 6 pm. Note that most mountain areas in southeast Arizona did not have rain.