Undular Bore

Undular bores are a type of "gravity wave" in the atmosphere. They are often visible in cloud formations and believed to mostly take place at night. They are thought to be caused when there is an air disturbance due to thunderstorms that roll across cold stable air. They are thought of as "gravity waves' because gravity acts as the restoring force when such a waves of flux creates the undulating wave-like motion seen in the clouds.

NASA says at http://science.nasa.gov/headlines/y2007/11oct_undularbore.htm?list1043252, ithat t's possible undular bores amplify weather, causing it to be more severe. These bores may even intensify tornadoes. They also say that not many people have actually witnessed undular bores in action, one reason being that most of them in the United States take place during the night.

Tim Coleman of the National Space Science and Technology Center (NSSTC) in Huntsville, Alabama says undular bores may be the source of thunderstorms. In other words, while thunderstorms are believed to cause undular bore, undular bores may also be the cause of thunderstorms.

Fascinating!

To see an undular bore on you tube, click here.