Saturday, August 11, 2018

Active Day Yesterday Continued Through Night

Thunderstorm on Catalinas at 3:36 pm MST yesterda,y trying to move into north part of city. Photo down at bottom of post is sunrise over Thimble Peak this morning.

Plot of detected CG flashes (above from Atmo and Vaisala) is for 24-hours through 7:00 am this morning. Thunderstorms around Tucson stayed mainly on the mountains. There was widespread activity across Phoenix area again, and storms continue active this morning out west near and along the Colorado River (as per the WRF forecasts yesterday).

The ALERT rainfall plot below is for 24-hours ending at 6:00 am this morning. The heaviest amounts were on and west of Catalinas (large hail reports just west of Catalina); however, one strong cell built southward across the city from the east end of Catalinas - DM reported 1.03" from this storm, but it missed airport where only 0.06" fell. Here at house the early morning shower plus afternoon storm totaled 0.21". Note that the most southern sites in ALERT network had rainfall also, with amounts up to around half an inch.

The Phoenix area received another significant rain event during the night - composite radar chart above is from 04:30 am. The rainfall plot of various network reports below (from Maricopa Flood Control District) shows how widespread the nocturnal event was (there were a couple of reports of severe winds out in the western suburbs). Second below shows composite radar from Yuma at 7:00 am this morning.

The morning skew-T plot above (from SPC) for TWC shows a bit of drying; however, significant steering winds continue from the northeast, while upper winds have become northerly - anvils over city from storms on Catalinas possible. The CAPE analysis for surface parcels by SPC is a considerable over-estimate, and mixed layer CAPE this afternoon would likely be around 500 J/Kg or so.

The 500 mb pattern (below) is very chopped up with three centers of anticyclonic circulation present with several troughs separating the centers. The trough over Colorado and northern New Mexico may try to move our way today. Most significant aspect of the analysis appears to be the cold temperatures across the Southwest - I've shaded temperatures of -9C and colder. The two 06 UTC variants of the WRF forecasts (from Atmo) are somewhat similar for today - severe thunderstorms this afternoon across parts of western Arizona. Both forecasts indicate storms for eastern Pima County near and after midnight tonight.

The sounding plot for Flagstaff (second below) was launched into an unusual, early morning thunderstorm, accounting for the bizarre data up there.

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