Did you see the sky Wednesday? It wasn't just another overcast day in Austin, many people spotted a unique feature in our atmosphere: Gravity Waves.
Our atmosphere was mainly stable behind Tuesday's cold front. There was just enough instability, or upward motion, to produce these waves above us, which created some pretty awesome clouds.
Next time you're at a pond on a calm day, toss a pebble into the water. The ripples that form outward around the pebble are gravity waves that are spreading out, in an up and down motion. The same thing happened in our atmosphere, where instability is playing the part of the pebble in the atmosphere.
To read more about gravity waves, here's a great link from one of my former meteorology professor at Mississippi State University, Mr. Jeff Haby: http://www.theweatherprediction.com/habyhints/64/