Dodge At Rillito Rainfall

The observed rainfall at the Dodge at Rillito ALERT gauge captured my interest this morning because of the large difference in rain amount from the house to the gauge. This gauge usually reports rainfall less than here at the house, so the 6/10 inch gradient (0.63" at the ALERT gauge and 0.04" at house) across less than a mile was interesting. I walked along the Rillito this morning to see what I could see. The soil was just damp in places when I was about a third of the way to the gauge (it was powder dry here) and was slightly damp at the gauge. There were no puddles anywhere between here and the gauge along the north side of the Rillito. The parking lot at the Brandi Fenton Park was completely dry (only about 50 yards away from the gauge). However, two basketball courts (only 50 feet or so from the gauge) that have high metal roofs had puddles - I assume this was because the asphalt under the roofs was not nearly so hot as the open parking lot.

When I crossed the bridge at Dodge, I could see some puddles off to the east in the wash. The wash had flowed briefly after the storm at 50 cfs. The graph below shows that most of the rain at the gauge was measured in less than half an hour. Walking back to the house along the south side of the wash there were several puddles, but only where drains from the neighboring streets empty onto the path. So, it was clear that more rain had fallen off just to the east and southeast of the house, but it was not at all obvious that nearly an inch of rain had fallen over at the bridge. 

                                   

So here is a possible problem. The two photos above and below are of this ALERT gauge sited just west of the bridge along the north side of the wash. I shot these several weeks ago. The gauge is right next to a fair sized mesquite tree that actually overhangs the gauge. I stood beside the gauge to look up to be certain that some of the tree actually overhangs the gauge and it does. Since the winds were gusting 40 to 50 miles per hour during the storm (from the north to east and to south-southeast), was it possible that some of the rain being caught by the tree was blown into the gauge? No way to determine if this actually happened, since there are no other measurements closer than the gauge here at the house. But clearly there is a siting problem at that gauge.