Hook echo

As a hook echo (English: hook echo ) a special hook-shaped pattern is referred to on the screen of a precipitation radar. Whereas it is also a hakenfömiger extension on the radar image ( "Echo " ) of precipitation (rain and often hail) a thunderstorm. This hook is usually located in the right, rear part of the storm ( as seen in the direction of movement). The hook echo is a key indicator of the presence of a rotating updraft region ( a so-called mesocyclone ). His appearance thus suggests that it is in the thunderstorm to a supercell with high tornado risk. It is produced by precipitation, which is wrapped by the rotation around the low precipitation mesocyclone. A hook echo was first recorded on April 9, 1953 by a speed camera at the Willard Airport in Champaign ( Illinois). The response could be associated with a thunderstorm and a tornado track. The National Weather Service in the United States regarded the appearance of a hook echo as sufficient reason for a tornado warning.