Sunday, October 30, 2016

Lessons in Orographic Effects from Big Beacon

Big Beacon is the nickname given to the 7143 foot peak immediately east of Research Park and the University of Utah with a small tower on top of it.  Officially on USGS maps it is known as Mt. Wire, but Big Beacon is easier to remember.

I've hiked it many times, usually in bad weather.  The peak is fairly exposed to southwesterly flow and it can be quite breezy, as it was today.  It has, however, a nice view of the central Wasatch and I like to visualize the flow and its impacts on cloud development from the summit.

Today we were on the summit at about 1430 MDT when the crest-level flow was out of the south-southwest, as illustrated by the vector wind time series from Mt. Baldy above Alta.

Source: MesoWest
From Big Beacon, one looks south-southeastward toward the high terrain of the central Wasatch.  The view is not perfectly perpendicular to the flow, but close enough for meteorology.  One could see very well the influence of that high terrain on the low-level cloud pattern with shallow orographic cumulus over the central Wasatch (and a few showers) and a decline in coverage over lower terrain further downstream to the east.  I've highlighted this transition in the photo below.

Click to enlarge
The beauty of the central Wasatch, and one of the reasons why the snowfall is so great there climatologically, is that it is an island of high terrain that is exposed to the flow from multiple directions.  Clearly today that island of high terrain is influencing cloud development.  Although not leading to much precipitation today, one can imagine that such effects would contribute to precipitation enhancement during winter storms.  As Yogi Berra said, "you can observe a lot by watchin'".

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