Sunday, January 28, 2018

East Winds Follow-Up

High pressure over the Great Basin today helps tighten the pressure gradient for easterly winds. The 10-m wind forecast above (from 06 UTC WRF-GFS forecast run at Atmo last night) indicates strongest low-level winds around airport and metro area at about 10:00 am MST tomorrow morning.

The situation sets up for the Whipple Observatory and the Mt. Hopkins RAWS station earlier, with forecasts from the same run indicating strong winds by mid-morning. Photo above shows view of the Santa Ritas from Highway 83, at about the site of the WRF-GFS forecasts for the skewT at Sonoita. The prominent gap to the left (south) of Mt. Wrightson is Riley Saddle - immediately up-wind of the observatory. Photo below shows the Whipple MMT telescope complex at top of Mt. Hopkins, with the RAWS station in foreground at distinctly lower elevation - Winds apparently gust most strongly around the RAWS site, due to a second terrain gap upwind of the station.

While yesterday's forecast kept the layer of easterly winds reaching to only about half the height of the Santa Ritas massif, today's forecasts of the Sonoita sounding indicate the layer reaching above 700 mb. SkewT above is valid at 10:00 am this morning, while forecast below is valid at 09:00 pm early tonight. The east winds weaken briefly in the forecasts during the mid-afternoon today, but increase again after dark. These soundings would indicate gusts of 50 to 65+ mph at the RAWS site beginning this morning and continuing into early morning tomorrow. 

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