Yesterday was a day of reduced thunderstorm activity in far southeast Arizona; however, storms again developed near the Santa Rita mountains and moved northward, with some dissipating over the Tucson metro area before sunset. The partial rainbow photo (on the blog) was taken looking east-northeast from the backyard a bit before 8 pm last evening.
Only 5 of the 93 ALERT gauges reported rain in past 24 hours and amounts were light. I did note that the Empire RAWS station was hit by a heavy storm for the second day in a row and it reported 1.00” in a brief period yesterday afternoon.
Today is yet another problematic forecast situation. The Tucson morning sounding indicates a small amount of CAPE for late day, high-based storms. The lapse rate is nearly adiabatic to 500 mb, so that any increase in low-level moisture from the south/southeast would quickly increase CAPE.
The 500 mb anticyclone is positioned aloft near Wichita Falls, Texas, and winds are southerly at all levels above 600 mb here over Tucson. It appears that the hottest and driest air circulating around the anticyclone will stay a bit to the east of here today. Of course, as everyone has been mentioning, the lack of any upper-air data from northern Mexico for the past 8 days makes for much uncertainty. This is complicated by the NAM forecast which indicates a distinct S/W at 500 and 700 mb moving across southeastern Arizona this evening. In the model, this feature yields a good shear profile as 500 and 700 mb winds become east-southeasterly. Thus, an increase in coverage and intensity of storms is possible this evening – assuming the model has a fair degree of accuracy over northern Mexico.
We are heading to the grasslands near Sonoita this afternoon and tomorrow, and I’ll report back on Sunday on the storm activity we observe down there in the hinterlands.
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