Friday, July 08, 2011

Severe Thunderstorms North and Northwest Portions Of Tucson Yesterday



Severe storms, coming from the southeast-east yesterday afternoon, again split around parts of Tucson; this time however, the storms veered away from the south portions of town. Here at the house we had gusts to 60 to 65 mph estimated, as the storm shown in top photo came down the Rillito. We had in-cloud lightning and rumbling thunder through the event. The downburst winds were accompanied by light rain and pea to small marble-sized hail - only about the 4th time there's been hail at the house during past 14 summers. A nice period of moderate rain followed, after the hard towers had moved to the northwest. We ended up with 0.41" of rain. Jim Toth reports winds of 40+ mph and 0.64" of rain from his place, about 2 miles or so northwest of here. I saw three newly downed trees during my morning walk along the Rillito (which was running again). Largest one down was in the Trader Joe's parking lot at Campbell and the Rillito bridge. Bottom photo above shows the Catalinas before sunset, well after the rain had ended.
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Rainfall coverage in the ALERT network was way up compared with Wednesday. There were 53 gauges (of 93) with measured rain, or about 60% coverage. The gauges with rain were generally across northern parts of the metro area. Atmo, DM, and airport were all south of the northern storm (the southern storm cell headed down toward Green Valley) and had trace to 0.01" precipitation. Heaviest amounts of around an inch or a bit more were in the Catalinas and out in Oro Valley area (where wind damage was more widespread). I note that the Sasabe RAWS station had 1.28" of rain and a gust to 56 mph around 5:30 pm, while Sells measured 1.05". So a very nice upturn in the storm activity!
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Shown just below is the KEMX composite radar image for just before 6 pm, when hail was falling here at the house. For compatison, the bottom image is the WRF-GFS forecast of radar echoes valid at 5 pm yesterday - model forecast certainly captured  the general charcter of the event.


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