Monday, October 05, 2015

Light Showers At Sunrise

A fast moving area of light showers crossed parts of the Tucson area at sunrise. At 6:30 am 25 sites in the ALERT network had measured rainfall during past several hours - amounts were very light except for 0.31" at Mt. Lemmon and 0.24" at the Avra Valley Airpark out at northwest corner of the network. Just a trace here at the house. The showers intensified to include some thunderstorms as the area moved rapidly northward into Pinal County - above plot show CG flash density for last 6-hours ending at 6:00 am MST (from and Vaisala).

The sounding below is from TWC on campus - fairly moist and unstable conditions at that time with a very nice, Plains-like wind shear profile. However, the forecasts from both the WRF-NAM and the GFS version run at 06 UTC last night at Atmo are not nearly as favorable as the sounding would seem to indicate. Both versions of the model shut the shower activity down over our area for the rest of the day, as warmer air above 700 mb returns and PW decreases some. The model forecasts yesterday were quite good keeping activity well east and north of Tucson through midnight. Will they be as good today? 

This a hard call, given the CAPE available at low-levels that will combine with sunshine and heating this morning. Looks like yesterday's battle between low-level CAPE and warm, dry air inversion aloft will continue today. Current GPS PW estimates to our west are indicating values similar to what's forecast by the WRF models - so for now I'd say the morning rains were our weather event for the day, but of course will keep an eye out early this afternoon.

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