Friday, August 10, 2012

Gust Front with Lake Stink

A nice gust front moved through the northern Salt Lake Valley this evening, bringing with it gusty winds and the infamous "lake stink."  The gust front marked the leading edge of outflow from thunderstorms to our immediate northwest.

Gust fronts are usually accompanied by a sharp drop in temperature and increase in wind speed (and/or wind shift).  Winds gusted to 44 miles per hour at the Spaghetti Bowl with the passage this evening.

Thunderstorm outflow is an example of a gravity current in which cold, dense air spreads and displaces warmer, less dense air.  There is usually a pronounced nose at the leading edge of the gravity current.

You could see this structure this evening (other than the breaking waves at the top of the gravity current) as there was quite a bit of dust (and some "lake stink") in the thunderstorm outflow (flowing from right to left, opposite the image above).  Click to enlarge the image below.

Gravity currents are common in all sorts of "geophysical fluids", including the powder avalanche.  The classic textbook on the subject is Gravity Currents by John Simpson.

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