Tuesday, December 05, 2017

Sprinkle Chances Diminishing Followed By Dry East Winds

View of Catalinas at 1539 UTC this am shows both dirty air and also that cloud bases are mostly well above the mountain tops.

The MIMIC TPW analysis for 14 UTC (above) indicates mostly dry conditions over the Southwest, with band of slightly higher values extending into southern Arizona. The 14 UTC visible satellite image (below) shows an impressive cloud deck again over southern Arizona. With dry lower levels, the model forecasts have shifted toward drier conditions, and indicate that precipitation is confined mostly to the White Mountains and northern Mexico. 

The 06 UTC WRF-GFS forecast of OLR (W/m2 - above) is valid at 15 UTC tomorrow morning has pushed the cloud deck nearly out of Arizona. So sunshine should return tomorrow, but dewpoints will plummet. As the 500 mb ridge builds southward, low-level easterly winds will develop - making temperature forecasts very tricky next several mornings.

The easterly winds become deep enough to bring a significant event to the Whipple Observatory on Mt. Hopkins. The WRF-GFS forecast sounding for Sonoita (below for 13 UTC on the 7th) indicates that winds at the Mt. Hopkins RAWS site could experience gusts of 60 to 80+ mph beginning late tomorrow and extending into Friday morning (if the forecast verifies).

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