Quick Look At Current Conditions

This morning skies over southeastern Arizona and northwestern Mexico are mostly clear - the exception is a south-north band of MCS debris cloudiness from eastern Sonora, northward across eastern Cochise County, on up to the White Mountains. So, sunshine won't be a problem locally, until anvil cloudiness increases this afternoon.

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The morning Tucson sounding is shown at top. It appears to be about as unstable as yesterday's sounding, even though PW has decreased some. Compared to GPS PW the sounding is about 3 mm too wet this morning - probably in the layer 700 mb to 850 mb where the Td profile is quite linear. So CAPE may be a bit lower than the data indicate. Steering winds are light south to southwesterly and upper-level winds are 30 to 40 kt from the south. Definitely not a good wind profile for long-lived storms, since the anvils spread directly ahead of cells that develop on the mountains. It is a good profile for back-building storms which can keep cores nearly stationary, with a threat of heavy rains. Cloud bases will probably be up around 650 mb, so that there remains some threat of strong downbursts.

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At 500 mb (middle graphic) there is a distinct, albeit weak, shortwave trough located out over the lower Colorado River Basin this morning. It will likely be moving toward the northeast today, leaving southeast Arizona under the influence of some weak subsidence through some of the afternoon. Orographic forcing of the higher mountains will probably be able to overcome this fairly easily. The center of the anticyclone has shifted eastward toward Texas, and the overall subtropical high at 500 mb remains an amorphous, large system with weak height and wind structures - as has been the case much of the summer.

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The NAM 500 mb forecast for midnight tonight, from this morning's run, is shown in bottom image. The short wave is forecast to extend from Moab, Utah, south toward Flagstaff, with a weak tail extending southward to the northeast end of the GoC. The overall state of the 500 mb subtropical high is well indicated by this forecast chart. Note that there are no height contours south of 40 degrees or so north, and that there is a large proliferation of tiny vorticity maxima running around everywhere.

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Looks like another day of mostly mountain/near mountain storms in the southeast. The anvil- shadowing wind profile means that places like the house here are unlikely to get precipitation, unless a cell develops nearly overhead. I suspect that I'll have to be watering some of the plants yet again this afternoon.