Timelapse of closest NEXRAD base reflectivity of the 29 June 2012 derecho. The timelapse moves from Davenport, Iowa to Richmond, Virginia over 14 hours. Here's a version further north: http://www.youtube.com/watch?v=3Rz84ru2yjM Another another version with velocity: http://www.youtube.com/watch?v=W3fQNLAMT4o