A Neat Satellite Image: a Short Weather Lesson

Something neat is in satellite imagery and there's a meteorology lesson in it. Thunderstorms always produce rain-cooled air that hits the ground and spreads out much like pancake batter. The leading edge of this cool air is called an "outflow boundary" and acts like a small scale cold front. Under the right conditions, they can force other storms to develop, or they can suppress thunderstorm development. Clusters of thunderstorms produce the largest outflow boundaries because their outflows combine. Thunderstorms have been moving out of the Black Hills this morning, closing in on the northern border of NE. This outflow boundary is progressing southward through the Sandhills and Panhandle. Note the herring-bone structure to the clouds behind the boundary. These are "wave clouds" and they occur because the air does not want to rise. We refer to the air as "stable". The outflow is forcing the air to rise, but because it doesn't want to, the air sinks back to where it was (and actually a little lower than where it was). This doesn't occur just once; an oscillation of up and down motion is created which results in these "wave clouds". Now, if the air being forced to rise was unstable, meaning that it wanted to rise but needed some assistance, then the air would erupt rapidly upward and new thunderstorms would develop.

This page was composed by the staff at the National Weather Service in Hastings, Nebraska.


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