Thursday, August 15, 2013

Low Elevations Continue In A Dry Break

Yesterday was an interesting day wrt to storm propagation. As I watched radar loops several times, storm cells were propagating in many directions, primarily developing along terrain gradients. It was reminiscent of that ancient computer game - PAC Man. Once again the storms stuck mostly to higher elevations. The 24-hour plot of CGs (above ending at 6 am this morning) shows some lightning with a cell across parts of metro Phoenix. Across the ALERT network 8 sites had rainfall during past 24-hours - amounts were light and occurred at higher elevations along the east edge of the network.

Below is the early WRF-GFS forecast sounding for TUS valid at 4 pm this afternoon. Parcels below 800 mb have decent CAPE - outflows from another large MCS over Sonora last night have continued to ease PW upward across southern Arizona. However, cloud base for those parcels is up around 600 mb - so strong and organized outflows are needed for low elevations. However, the wind profile forecast for this afternoon continues to extremely light and variable, as the anticyclone aloft is nearly overhead. So it goes.

The above graphic shows total rainfall forecast by today's early WRF-GFS through 8 pm on Saturday the 17th. Note that amounts of significance remain on the mountains and higher elevations out west of Tucson. Below is the current Phoenix rain index from this morning - showing that the dismal storm season continues up there also. One station reported rain from that cell that moved through parts of the PHX metro.

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