Friday, August 03, 2018

In The Donut Hole Yesterday

Storms south of Kitt Peak at about 2:30 pm CST yesterday afternoon - above. Considerable severe thunderstorm activity over Southwest yesterday - mostly strong winds but with a couple of large hail reports also - SPC report map below for August 2nd. Many of the reports were in the western suburbs of Phoenix.

Only six sites in the entire ALERT network reported rainfall yesterday, with four of those up in the Catalinas. Pretty miserable day, but several of the WRF forecasts for yesterday afternoon/evening definitely had metro Tucson in its well-known donut hole. Plot of detected CG flashes for 24-hours ending at 1:00 am this early morning (below from Atmo and Vaisala) shows the void over us and also another over eastern Maricopa County.

The 500 mb analysis for 12 UTC this morning (above from SPC) shows that a weak trough has moved across the state during night, leaving us in a non-monsoonal flow regime, with parts of the anticyclone pushed south over Sonora and also east to the southern Plains - ugh.

Sounding plot for TWC (below for 12 UTC from SPC) indicates westerly winds through entire troposphere, but with abundant moisture below 500 mb and considerable potential CAPE. However, subsidence and drying will likely be occurring above 500 mb, putting a serious damper on storm activity except over higher elevations. 

Only chance we have here at house for a storm in this type pattern is if something develops over the northern Tucson Mountains or the Tortolitas - i.e., immediately up-wind and close. Both 06 UTC WRF forecast runs at Atmo forecast a couple of isolated thunderstorms for eastern Pima County this afternoon, but with a bit more activity on to the east.

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