Friday, March 25, 2011

Lessons in Radar Interpretation

This morning's radar loop provides a great opportunity for instruction in radar interpretation.  In particular, there are three major precipitation features evident in the loop:
  1. Persistent, quasistationary orographic precipitation.
  2. A cold-frontal precipitation band.
  3. Radar echos generated in the southwesterly flow aloft.
Have a look for yourself.

The area inside the red box provides a nice example of persistent, quasistationary orographic precipitation.  This is an area of pre-frontal orographic precipitation enhancement over Mount Timpanogos and the Little Cottonwood-American Fork divide.  This is a common feature in southwesterly flow.  By quasistationary we mean "almost stationary" meaning it moves around a little, but generally stays fixed to the topography.  Orographic is just a fancy word for mountain-induced. 

If you watch the loop, you can clearly see the cold-frontal precipitation band, which is moving from west to east during the loop.  This precipitation is generated by cold frontal lifting.  Note that the motion of this feature contrasts with many of the other echos in this image which are moving from southwest to northeast and are being generated in the southwesterly flow aloft.

Thus, at least three different dynamical processes are contributing to precipitation today.

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