Friday, August 10, 2018

More Of Same

There was light rain across parts of the metro early this morning, leaving behind a nearly saturated atmosphere. Photo above just after sunrise shows stratus fractus and fog hugging the lower foothills of the Catalinas.

Afternoon storms yesterday again produced both hail and severe winds across the Southwest from New Mexico to California - above plot shows SPC reports for August 9th. The tornado report at Eagle Nest, New Mexico - east-northeast of Taos - occurred at an elevation of over 8,000 ft MSL. The hailstorm in the Flagstaff area was probably the most significant severe thunderstorm event in Arizona.

During the early morning hours a large MCS developed between Tucson and Phoenix and moved southwestward - NCAR regional base-scan radar chart above is from 2:00 am MST. The system brushed the metro area with light anvil rain and some nocturnal lightning displays. The ALERT rainfall plot below is for 24-hours ending at 7:00 am - the heavy amounts from Oro Valley westward across the northern Tucson Mountains were produced by an afternoon storm that moved off east end of Catalinas - we had thunder here but no rain from that storm. The early morning rain showers here amounted to 0.03" in the gauge.

While things are very moist and a bit more unstable in this morning's upper-air data, the overall situation remains very chaotic. A weak short-wave at 500 mb hangs, within the larger anticyclone, across southeast Arizona - with Tucson just on the south side of this feature. The sounding was taken very near the storms and MCS that were occurring, so its representativeness  for the day is at question also. Southeast Arizona is again covered by heavy debris cloud this morning - visible satellite image above is from 7:00 am. Nice wind profile again for organized storms, but heating uncertain place to place and role of short-wave unclear.

The two versions of the 06 UTC WRF forecasts from Atmo are again quite different for eastern Pima County. I'll illustrate this below, using the forecasts of total rainfall through 6:00 am tomorrow morning. Below at top is GFS version and at bottom is NAM version. Both versions do end up with a severe MCS/line of storms moving all the way west to Colorado River.

Another day to watch things evolve and to hope for a bit more rain here at house.

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