BOW ECHOES
The figure above is a prototype of the evolution of a "bow echo" (from Fujita 1978). Dr. T. Theodore Fujita, a professor at the University of Chicago, coined the term "bow echo" in the late 1970s. The terminology was based on how bands of rain showers or thunderstorms "bow out" when strong winds associated with the storms reach the surface and spread out like pancake batter. The bowed rain band is near the leading edge of the damaging winds. The storm system on which Dr. Fujita based the "bow echo" terminology produced a strong derecho over northern Wisconsin and adjacent states on July 4, 1977.
Derechos
typically are associated with a long lived bow echo or a series of bow
echoes. These bow echoes may vary in scale, but typically go through
an evolution that has at least some of the aspects of the prototype shown
in the figure above.