Saturday, July 26, 2014

Storms Around Yesterday But Mostly Dust In The Two Metro Areas

Tucson metro area was surrounded by thunderstorms yesterday, but the CG flash plot (above, ending at 07 UTC on 26 Jul) shows the well-known metro doughnut hole. Thick anvil  spread across the skies from the storms to the south and shut things down. Tucson airport recorded a gust to 48 mph from the south, and this gust gust front seemed to bring back more of the morning dust. Some of the storms out to the west were severe and produced vivid lightning shows. Sasabe had a severe thunderstorm with a gust to 66 mph recorded at the RAWS station there. Phoenix had gusts to 46 mph with another dust storm moving across the metro area up there.

Across the Pima County ALERT network 34 of 92 sites recorded rainfall, but none of the low-elevation metro stations did. Here at house we had dust and two very slight spits of rain. However, at higher elevations, especially in the Catalinas rains were heavier with 11 sites having over 1/2 an inch and 3 with over an inch. The rainfall through the 24-hours ending at 7 am this morning are shown below for the Catalinas and metro west sectors of the network. There was enough mountain rain for the Rillito Wash to be flowing some this morning.

The skewT plot of the morning Tucson sounding is shown above. Fairly sharp cooling is indicated near the surface from yesterday's storm outflows. Skies are quite clear, and so this layer should heat-out, resulting in a deep, fairly dry afternoon/evening boundary layer (BL). The vertical wind shear is similar to yesterday, with anvils likely to spread ahead of storm cores. Not a favorable situation for the Tucson metro area. The early WRF-NAM forecasts storms late today but with most activity to the east and south. The El Paso sounding is quite stable this morning and warmer air in middle-levels appears to be heading this way from the east. All-in-all a fairly low-key day for late July. The WRF-NAM forecast for rainfall through midnight (below) forecasts a dying storm from Rincons to affect parts of the metro area during the late evening. Will be interesting to see if the new forecasts are more optimistic.

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