Thursday, June 08, 2017

Yesterday's Thunderstorms

Considerable debris cloudiness this morning at sunrise - above shows about-to-rise sun highlighting Thimble Rock.

Composite radar image from 03:00 PM MST yesterday afternoon indicates considerable thunderstorm activity, especially in eastern Santa Cruz and southeast corner Pima Counties. WRF runs seemed to under-forecast the storm coverage a bit, but kept heaviest storms south to southeast of metro area which was how things played out. Visible satellite image below is from 02:45 PM.

Storms produced a nice outflow that moved northwestward, with gusts of 30 to 40 mph common. The storms also produced an east wind gust to 61 mph at the Mt. Hopkins RAWS site, which qualifies as a severe thunderstorm event. Wind speeds there are enhanced by gap flow, as per many earlier posts.

The 00 UTC sounding (above - from SPC) indicated CAPE, although amounts were not great and an inversion above 500 mb was a limiting factor. The plot below of CG flash density (from and Vaisala) is for the 6-hours ending at 05:45 PM and ALERT data at bottom are for 6-hours ending at 06:00 PM. Measurable rainfall stayed mostly southeast of metro area. Heaviest amounts were over the Empire Mountains (near the NWS radar), northward to I-10.

Today the activity will be shifting eastward, leaving us with dry, but slightly cooler temperatures into next week. The high yesterday at the airport reached 107 F, before the outflows moved by.

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