Storms In Eastern Pima County Yesterday

Above is the time series of T and Td at TUS yesterday. There was a big plummet in Td during the afternoon, much as predicted by the WRF-GFS at Atmo. The model had forecasted several plumes of very dry, low-level air to be swirling around southern Arizona. This was what was going on apparently, as varying low-level winds picked up dry air from across northern Baja at times and very moist air from east of the GoC at others. Phoenix still has very low dewpoints and PW values are lower in the west half of southern Arizona this morning. Storms returned to parts of southeastern Arizona yesterday, after a nearly total down day on Monday. There was rain at 12 of the 93 ALERT sites during the past 24-hours. These were mostly in the southern reaches of the network - Keystone Peak had 1.43" in less than hour yesterday afternoon, as a strong storm moved west of Green Valley. Most of the Tucson area had light sprinkles from debris cloud that moved over the city before sunset. Here at the house we had some spits of rain and another Trace day.

This morning an intense MCs, that has been moving to the west-northwest during the early morning hours, is still active over northern Sonora (see 1330 UTC IR image above). This MCS will be a big player in today's weather for Tucson. How long before it decays? Will it keep us cloudy and cool, or will an outflow trigger early storms? It will undoubtedly leave behind a substantial MCV, and where will that feature move? The early run of the WRF-GFS did not have this feature in its forecast, and so it will likely not be accurate for this afternoon. I have to leave for appointments before the 1200 UTC model runs will be in, and so will just be observing whatever transpires.

The morning Tucson sounding (above) is again very moist and unstable, but still with a totally messed up vertical wind profile. Another weak trough at 500 mb has sneaked in from the Pacific, and temperatures at 500 mb are very warm to the west. Monday's unstable sounding barely allowed a cloud - today's appears very vulnerable to an early outflow, and I'll be optimistic again that we should see another increase in storms today.