Wednesday, August 03, 2011

Two Nighttime MCSs Move Across Tucson Area


Two small MCSs have moved across the Tucson metro area during the night, The first a bit after 10 pm and the second is lingering still at 7 am MST. All of the action came as a bit of a surprise, given the supression of yesterday afternoon - see 0200 Z IR image above with large area of nothing over most of southeast Arizona. However, there were two MCSs over northern Sonora and also a line of storms along the borderlands. The first local MCS developed with a strong outflow from the south that moved by a bit before 10 pm. There was a lot of lightning and thunder with this system, but mostly light rains, except for higher elevations and a couple of gauges out to the west.


By 0800 UTC (see WV image above) the Arizona MCS had apparent strong convection at its leading edge, with a lot of trailing anvil cloud. Note that there were L/V winds below 400 mb, so these systems were being driven by outflows from Mexico. The second MCS developed when a second outflow from the south moved through the metro area around 2 to 3 am MST. Note also that by the time of this image the very large MCS to the northeast had drifted from eastern Colorado into western Kansas, and that another large MCS continued in central and southern Sonora.


At 1200 UTC this morning (3 August 2011) a small MCS, with two areas of colder tops, was affecting eastern Pima and northwestern Cochise Counties. There was light rain here at the house (0.25" in gauge at 6 am MST) with some anvil lightning and thunder at sunrise.


Finally, composite radar about 1330 UTC shows the weakening MCS. A loop of these data clearly indicates an MCV circulation spinning over the eastern side of the metro area. Very interesting start to the day and the end of a long dry period here at the house.

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