Tuesday, July 14, 2009

Apparently More of the same

Yesterday’s surge at Yuma mixed out during afternoon and precipitable water remains around an inch and a quarter across southern Arizona, with higher values remaining to the south over Mexico. More early morning convection across the southern Gulf of California (see 1400 UTC visible image above) may help sustain pushes of shallow but more moist air northward.

The 500 mb anticyclone split into two lobes yesterday with the western lobe moving over New Mexico. This morning it looks like the western center is over, or even a bit south of, El Paso. (Soundings are missing for Mexico so far this morning on the SMN site also.) This has shifted the 500 mb winds to southwesterly over Arizona. The NAM consolidates the 500 high as a single center between Tucson and El Paso and then shifts it northwestward from 48 to 72 hours. No features are apparent in the model forecasts that would serve to shift the subtropical air mass back over the Southwestern US – so we’ll just have to watch it day by day.

Yesterday, storms to the south pushed strong, dusty outflows across the Tucson metro area around 5 pm. Rain was reported at 7 of the 93 ALERT stations, mostly to the south toward Green Valley. I do see reports of 0.47” at Tinaja ranch and 0.63” at Picture Rocks so there were some isolated spots of respite from the brain-searing heat. This morning’s Tucson sounding has no CAPE when I modify for the afternoon, and so we’re looking at isolated storms over higher elevations and more strong and dusty outflows.

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