On Sunday, we were taking vertical slices up Little Cottonwood Canyon from our observing site near Daybreak. An approximate position of one of these vertical slices is shown below. It is oriented up the canyon and crosses over Snowbird and Alta. Keep in mind that the radar beam spreads with distance from the radar, so the beam is actually somewhat wider than indicated by the red line.
Below is the radar reflectivity from this slice. Warm colors indicate higher radar reflectivities that likely indicate greater concentrations or sizes of ice paticles and snowflakes. The bright red stuff near the bottom is ground clutter. I've indicated where I believe we are getting returns produced by the Baldy Shoulder (separates Alta from Snowbird), High Greeley (the ridge between Collins and Suguarloaf at Alta), and the Mount Wolverine/Patsy Marley ridge to the east of Albion Basin.
Note how the radar reflectivities increase and deepen over the Wasatch Range, an indication of mountain enhancement of precipitation. You might also notice that that the storm shallows before it crosses Mount Wolverine. In fact, it's greatest depth is actually upstream of Snowbird and Alta, which may be related to ice-crystal fallout or perhaps the mountain wave induced by the Wasatch Range tilting upstream with height. It will be interesting to see if our computer models can replicate this structure as it is likely important for limiting how much snow falls out as one moves eastward across the Wasatch crest.
The lack of returns at low levels east of the Baldy Shoulder occur only because the beam is fully blocked by the terrain. We know from the Collins data that it was dumping fairly hard at this time at Alta. Bummer that the radar can't see through the terrain!
This is cooler than cool. Keep up the great work!
ReplyDeleteYou guys are having too much fun! Great data!
ReplyDeleteThere's certainly distinctively high reflectivity's over the shoulder, high traverse and mt wolverine. Did snowbirds cirque ridge not show up or would it have at a different angle?
ReplyDeletePretty cool stuff you guys are doing
Anonymous - my bad in explaining the radar image. The bright reds are simply where the radar is hitting the ground, which leads to strong returns. In this scan, there is a broad region of enhancement, but not any local enhancement over those ridges.
ReplyDeleteWhen we look at horizontal scans, we can see three ridges, one of which could be the Cirque ridge. Until we get everything georeferenced, we won't know for sure.
Steve - haven't had a day off in weeks, haven't skied yet, and haven't cared. As you know, that's not normal for me, but the DOW is great fun! We could use a radar guru like you to help out.
ReplyDeleteI noticed that the SLC sounding was fairly stable up to around 6,000 feet (800 mb) on Sunday morning with very little air movement below that elevation. However, the lapse rate looks great in the 800-650 mb range where the orographics were occurring.
ReplyDeleteThis is similar to the behavior of the radar echoes in strong upslope storms in the Front Range of CO.
ReplyDeleteGreg - this case had fairly shallow upslope flow and a stable layer not far above crest level. We'll have to dig into this, but that structure would be roughly similar with front range storms (although the stable layer could be lower).
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