Wednesday, August 20, 2014

Major Flooding Yesterday In And Northwest Of Phoenix

Plot above shows detected CG flashes for yesterday from noon to midnight MST. The area of high flash density from Phoenix metro northwest to near Lake Mead experienced heavy thunderstorm rains and serious flooding at places. The flooding and rescues that are playing on national media this morning are mostly from the north Phoenix area.

Yesterday's PRI plot (above - from NWS PHX webpage, where there is much additional info on this event) shows the magnitude and extent of the event, with heaviest amounts over the north portion of the ALERT network up there. Data below from the USGS stream flow gauge on the Agua Fria River records a major flood event, with maximum flow reaching 40,000 cfs or a bit above.

Plot above shows MesoWest rain reports (from north Phoenix metro area up to Flagstaff) for 24-hours ending at 7 am this morning.

Across southern Arizona, thunderstorm activity was much diminished as the leading shortwave that had passed northward on Monday night brought in drier air behind it. Storms occurred from eastern Pima County eastward. Here at the house there were several periods of showers and thunderstorms from late morning through midafternoon - total rain amount was 0.31". Across the local ALERT network more than 70% of the sites measured rainfall for period 5 am to 5 pm, but activity diminished rapidly by sunset and less than 20% of the sites recorded rainfall from 5 pm through 5 am this morning. Although 21 sites reported more than half an inch yesterday, there were sites with an inch or more.

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