Thursday, July 16, 2009

Interesting Evening in Phoenix

While southeast Arizona was almost totally suppressed yesterday by the lingering impacts from the Sonoran MCSs, storms did develop over the Rim country. Some storms on the north side of a weak, midlevel 500 mb trough propagated into and then across the Phoenix area. Although there were a few spots with light rain, the main impact was a duster with 3o to 40 mph outflow winds (the outflow boundary is quite clear to the west of Phoenix on the 0600Z radar image above).

The weak shortwave trough remains between Phoenix and Tucson this morning and moves little during the day. The upper-level shortwave that’s come north along the Baja Pacific coast shears out quickly to the east today. Precipitable water values remain moderate with values over Arizona of 3.1 (TUS) to 4.1 (PHX) cm. More moist and unstable subtropical air remains just south of the border (Guaymas PW this morning 4.7 cm). The Phoenix sounding indicates that there’ll be some afternoon CAPE, at least on the north side of trough. Higher elevations should continue to have highest CAPE this afternoon.

With light winds below anvil level and convective cloud bases around 600 mb, storms will move slowly and produce some strong dusty outflows again.

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