Totally Suppressed Over Most Of Southeastern Arizona

The total lack of storms across most of southeastern Arizona yesterday needs a bit of a postmortem this morning. Those of you who have followed this blog know that I grumble some each year about the demise of postmortems within much (most? all?) of the NWS. While I anticipated more activity over southeastern Arizona yesterday, things actually when seriously downhill. Across all of the ALERT network there was only 1 station that reported rainfall (0.12") and that was out in the far southwest corner of the network at the Arivaca site. So what  happened yesterday?

The 00 UTC sounding from late yesterday afternoon is shown above for Tucson. The strong easterly winds that I was worried about were still present in the afternoon and were well-mixed through the depth of the boundary layer. While easterly steering level winds (note that steering level winds are always in the middle-tropospheric layer above the top of the boundary layer that reaches to 600 mb), above had dropped away to almost nothing. Easterly low-level winds are a definite strong negative for storms in the Tucson area. This is because they are basically downslope and associated with subsidence - yesterday was probably characterized by a strong battle between buoyant thermals and mesoscale subsidence associated with the east winds - unfortunately, strong and gusty east winds prevailed all day. Not good. Additionally, the temperature at 500 mb warmed by more than a degree during the day, however, this is not unusual. The 24-hour change at 00 UTC last evening had cooled by about half a degree. Just what was driving the strong easterlies? This is much tougher - height gradients aloft were not strong and had changed little from the 10th. So, I am puzzled about what was forcing the extended period of strong easterlies. None-the-less, the winds appear to have been the most serious negative factor yesterday.

While the Tucson 00 UTC sounding had only a sliver of Tv CAPE in the SPC analysis, the sounding data were extremely too dry. It appears that, wrt to GPS - see above, the atmosphere had more than half an inch higher PW than that indicated by the bad RRS sonde data! This is a seriously bad sounding!

Other parts of western Arizona had increased storm activity yesterday. During the afternoon strong storms moved south from the Bradshaw Mountains and generated an outflow that moved into the low deserts. There may have been severe winds in the wastelands between Wickenburg and Quartzsite, but we'll never know. Phoenix did have gusts 47 mph and a quarter inch of rain. Storms developed over much of Maricopa County around 8 pm MST (regional radar above). This morning an MCS was dissipating over the lower Colorado River Basin (1245 UTC water vapor image below), with some thunder and even moderate rain at Yuma.