Back In Tucson

We are back in Tucson, after being away on travel (Colorado Front Range and San Francisco areas) most of the last two weeks. It appears that only a trace of rain occurred here at house since last Thursday morning - not good, given how much moisture there was over southeastern Arizona. A very nice example of how abundant moisture need not translate into rain at a given location down here in the summer. There are many other factors at play - CAPE, vertical wind profile, amount of solar heating, outflows and etc. Naturally, most parts of the local area fared better than we did here at house.

Yesterday was fairly supressed, especially at lower elevations. Almost 30% of the ALERT stations measured rain during past 24-hours, but these were mostly the higher elevation sites. Only 20% of the Greater Tucson sites had very light amounts of rainfall (< 1/10 inch). The composite radar chart from NCAR (above) for 2 pm MST yesterday (July 25th) indicates the general low degree of storm activity. But note that this product displays base-scan reflectivity, which can be quite deceptive in our area. Highest amounts of rain I noted were 1.04" at Keystone Peak and 0.63" at Manning Camp.

The two webcam photos above show the views looking north, from the U of A campus and from Kitt Peak, at a bit after 7 am. Heavy middle cloud cover is drifting around over metro Tucson, while skies are quite clear out at Kitt Peak. This reflects a fairly pronounced decrease in PW from Tucson westward, as drier air is inching eastward on west winds associated with another Pacific trough that is moving across the far West today. So, looks like we've returned for just in time for a further decrease in storm activity.

Finally, the Tucson 12 UTC sounding this morning (above from SPC) exhibits little potential CAPE for the afternoon at low elevations. Winds remain quite light and are now westerly below 400 mb. Ignore the SPC Tv lifted parcel from the surface - it is completely irrelevant - but note that mixed layer CAPE is only 113 m2/s2. To the northwest at Phoenix this morning, mixed layer CAPE is zero. The U of A Atmo midnight run of their high-resolution, WRF-GFS model indicates that Pima County will be very suppressed today and tomorrow, with activity forecast to remain east and south along the borderlands. So it goes as July heads toward August.