Sunday, July 27, 2014

Wild Night With Numerous Severe Thunderstorms

There were so many severe thunderstorms yesterday across Arizona that I can not cover everything in a single post. The various models run from 12 UTC data did not forecast the events well, although the WRF-GFS from Atmo forecast the early stages of the MCS that developed along the Borderlands. However that MCS was still going strong at sunrise this morning. The 0330 UTC (8:30 pm MST) IR image above, that I grabbed before I went to bed, indicated the potential for storms continuing through the night - especially given the soundings from Tucson and Phoenix at 00 UTC. The IR image below is from 12 UTC this morning and the southern MCS has moved out  into southwest Arizona. The northern MCS moved rapidly across parts of Maricopa County, producing widespread wind damage across metro Phoenix. That MCS weakened rapidly out in west-central Arizona after midnight. The MCSs both developed in elevated terrain - one in the southern White Mountains and the other in the higher elevations of the Borderlands.

Katie woke me up a bit after midnight night and we sat on the porch and watched a spectacular lightning show over the Catalinas, with nearly continuous flashes and rumbling thunder. The cores stayed on the Catalinas and that storm was off to the north edge of the southern MCS. We had only some light sprinkles here and there was just 0.01" in the gauge this morning.

Graphic above shows CG flashes through 12 UTC this morning and illustrates the paths of the cores of the two MCSs very nicely. Plot of severe thunderstorm reports (all winds) from SPC this morning is shown below. The reports page lists over 20 separate wind events in Arizona, most of them in Maricopa County. The southern MCS moved across the most desolate part of the Sonoran Desert and likely produced severe winds out there too.

The storms were high-based and produced more wind than rain it appears. Across the Pima County ALERT network  only 39 sites had rainfall during the night. There were 5 stations with over half an inch and Mt. Lemmon had just over an inch. The Catalinas sector is shown above at 6 am this morning and the southwest sector of the network is shown below.

The air mass over Arizona is, not surprisingly, highly worked over this morning and both the Phoenix and Tucson soundings are not very representative of the larger-scale setting over the Southwest. 

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