Wednesday, May 23, 2012

A Headscratcher

There's a perplexing radar look this morning as some showers have popped up in the unstable, postfrontal, northwesterly flow over northern Utah.  

Satellite imagery shows that this area of precipitation is isolated to our area.  

I say perplexing because it is unclear what mechanisms are responsible for the showers.  Is the lake playing a role?  IT seems the flow direction isn't quite right and that the cloud band may extend to just upstream of the lake shore (see above).  How about the Oquirrh Mountains or three-dimensional terrain effects related to other mountains?  It's a head scratcher.  Any ideas out there?


  1. Complete guess: you can see trapped lee waves. So, perhaps the gap between the Oquirrhs, Stansburies, and Cedars causes constructive interference until these waves get so large over the Oquirrhs that it lifts parcels above a level of free convection?

  2. I suspect mainly orographics but, with the 12Z sounding well-mixed, the lake probably helped a bit. The wind direction in convective cloud layer (~580-700mb) was not aligned with the lake, but it was much more northerly below this. So, slightly warmer and more humid air over lake is advected southward a good distance before it is lifted with the help of the terrain. This is my best guess.