Sunday, August 12, 2018

Direct Hit

View at top from campus captured developing storm cell along the foothills - this cell moved directly over this part of town producing some winds and heavy showers. The CG plot above (from Atmo and Vaisala) is for 24-hours ending at 3:00 am MST this morning. Limited thunderstorm activity in southeast Arizona, with most action occurring over eastern Pima County. The other very active area was in northwest Arizona and southern Nevada. There were numerous reports of severe wind gusts from the Las Vegas area. Radar below is from 5:10 am this morning and shows early morning showers continuing west of Tucson. 

WRF forecasts yesterday were quite accurate for the severe storms in the northwest part of state, while some runs were better than others for the storms in eastern Pima County. Across the ALERT network about 75% of the sites had measurable rainfall, with generally light amounts and only a few sites had over half an inch. TUS had no rain and DM recorded a Trace. Here at house the direct hit by the small thunderstorm cell produced 0.61" between 6:00 and 7:00 pm. Late night showers provided another 0.06" before midnight - total here of 0.67" was most significant rain since the unusual June event.

This morning skies are clear, or clearing, across much of southeast Arizona as the shower area moves westward - visible image above from 6:45 am.

The morning sounding data is again a mixed bag. At TWC (skew-T below from SPC) there is an onion like low-level thermal profile and steering winds have become very light. However, to the northwest (Phoenix skew-T second below) there is much more CAPE and a considerably better vertical wind profile for organized storms. Various WRF forecasts have not captured the early morning activity well, so the model world for this afternoon is quite uncertain. Some versions forecast storms over the metro area late afternoon well into the night, but other versions keep storms mostly to south and west. Storms in our area will depend on heating and outflows to help. Severe storms appear likely again for the greater Phoenix area.

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