Storms Mostly Elsewhere Yesterday

While there was a bit of an uptick in rainfall coverage yesterday, amounts were mostly light and heavy storms occurred generally far off in the distance from the Tucson area. I did note several very strong storms that essentially stayed locked in place for several hours. One was near Ash Canyon and the other was off on the northeast flanks of the Catalinas. These storms tried to move north, but their anvils were stabilizing that path, and they built new cells on their south flanks, essentially moving little. In the ALERT network 44 of 93 stations had measurable rain, but amounts were light, with two mountain sites measuring a bit less than half an inch. However, right in the middle of town one gauge, Kolb and Golf Links, reported 0.98" - I don't know whether this is a gauge problem or if there was a local cell that dumped on that gauge. Here at the house we had light anvil rain, from the decaying MCS in northern Mexico, during the early morning hours - total of 0.05". The largest 24-hour rainfall total I could find in a quick look this morning was 1.33" at Columbine RAWS on Mt. Graham.

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The images above show two MCSs in northern Mexico at 0330Z, a large and strong MCS remaining at 0600z, with anvil cloud extending northward over much of southeast Arizona. The concurrent regional radar image (bottom) shows little in the way of hard convection. New and fairly strong storms developed after midnight off in northwest and west-central Arizona - much as forecast by the WRF-GFS model run of yesterday morning.

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John Diebolt left an excellent comment last evening anticipating both the debris rain this morning and the forecast issues for today:

I was looking forward to the first good night for lightining photography Friday evening.. Was out on Ina/Wade focusing on storms over the Catalinas and Oracle Junction. I got one bolt before the towers collapsed. Got home to look at Radar around 8:45PM with a complex moving west across Sonora and had these thoughts: Ordianarily might see a scenario this weekend where this complex over Sonora clouds us over and outflow generates some precip overnight/early morning leaving us very moist but lacking for solar insolation Saturday and relatively down. Sunday as southwesterlies begin to develop..action focuses just e/ne of Tucson and moves off to the NE with little development upstream to the SSW/SW and the result being many valley locales miss the action. The trough dynamics nearby this time around could make all the difference, overcoming our usual quandry in high-moisture situations. Plenty of opportunity to bust a high PoP forecast this weekend! From my limited time in Tucson (6 years) it seems it takes an exact mix of everything to generate a widespread precip event and if anything is the slightest bit off..it fizzles. The vagaries of monsoon forecasting... bad sounding data..lack of Mexican data. Not the most enviable job but challenging!