Friday, February 27, 2015

Weekend Will Begin With Increasing Winds

Winds were already kicking up yesterday afternoon here along the Rillito, and that will be the case again today. However, the WRF-NAM forecasts from 06 UTC run at Atmo indicate even stronger winds tomorrow and Sunday (March 1st). Shown here are the 10-m wind forecasts valid at noon on Saturday (above) and noon on Sunday (below). Strongest winds are forecast at higher elevations on both days.

The WRF model doesn't get much in the way of precipitation going here in eastern Pima County until Sunday night. But the way it is forecasting the situation to develop is quite interesting. These two graphics are also from the 06 UTC WRF-NAM, but are on the 5.4 km grid. The above is the forecast of PW valid at 5:00 pm MST on Sunday the 1st. There appears to be an atmospheric river (AR) along the surface cold frontal zone that reaches across Baja and into southwest Arizona. But of more interest for us is the broader plume of low-latitude moisture that is moving northward on both sides of Baja - this will serve to enhance the AR and provide a broad influx of moisture into southeastern Arizona.

The forecast of accumulated preciptation through 11 pm MST Sunday night indicates a substantial event has already occurred in the Rim Country and that things are just getting started in southeastern Arizona. So, March will certainly be off to a very interesting start, weatherwise, for us.

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