Monday, July 20, 2015

Serious Downturn In Thunderstorm Activity

There was a very substantial decrease in thunderstorm activity across all of Arizona yesterday. While PW remained high, the large-scale environment became increasingly hostile. The CG plot above (from Vaisala and Atmo) is for 24-hours ending at 1:00 am MST this morning. Southeast Arizona had only isolated thunderstorms over the mountains. Another fickle TS has mostly sideswiped eastern Pima County. Across the ALERT network there were only 5 sites with rainfall during past 24-hours; however, of note was 1.26 inches at Elephant Head Butte on the west edge of the Santa Ritas.

The morning sounding from TWC (above 12 UTC skewT plot from SPC) continues with high PW but a very poor vertical wind profile, dominated by westerlies. There is more in the way of southwesterly steering flow, so some mountain storms may try to move a bit this afternoon. The WRF runs from 06 UTC forecast another day with very isolated mountain storms, as substantial drying occurs. The big question for next couple of days will be how strong the dry-out is. The blended PW analysis from CIMSS this morning (below for 11 UTC) indicates PWs of around 1 inch pushing into the lower Colorado River Basin. The models forecast the drier air to advect toward southern New Mexico, but with a battle zone setting up over the southeast corner of Arizona, before the moisture pushes back toward the northwest after mid-week. 

Finally a quick look at the tropical systems present this morning. The visible image above is from 7:15 am MST and shows the remarkable cloud mass associated with the remnants of once Cat. 4 hurricane Dolores, which turned into a record-setting event for many spots in southern California. The IR image below is from 1330 UTC and shows a very large MCS along the coast of the southern GoC, as well as the next tropical storm developing just west of 110 W. Certainly plenty to watch as the week evolves.

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