Hook echo

It is found in the lower portions of a storm as air and precipitation flow into a mesocyclone, resulting in a curved feature of reflectivity.

[5][7] This event was unintentionally discovered by Illinois State Water Survey electrical engineer Donald Staggs.

Heiser, and S.G. Bigler determined that a destructive tornado had occurred in the geographical location which corresponded with the "six-shaped" echo seen on radar.

Prominent severe storm researcher Ted Fujita also documented hook echoes with various supercell thunderstorms which occurred on 9 April 1953 - the same day as the Huff et al.

[8] After detailed study of the evolution of hook echoes, Fujita hypothesized that certain strong thunderstorms may be capable of rotation.

[9] Fulks analyzed wind velocity data from Doppler weather radar units which were installed in Central Oklahoma in 1960.

By detecting hydrometeors moving toward and away from the radar location, the relative velocities of air flowing within different parts of a storm are revealed.

HP supercells instead often have a high reflectivity pendant or front flank notch (FFN), appearing like a "kidney bean" shape.

Prior to 2008, NEXRAD had a range resolution of 1,000 meters, while the processes which lead to a hook echo happen on a smaller scale.

Classic-style hook echo of the F5 1999 Bridge Creek-Moore tornado .
Classic hook echo can be seen for this Kansas EF2 tornado in 2024
Diagram of air current in a supercell
A Doppler on Wheels image of a tornadic thunderstorm near La Grange, Wyoming (USA) captured during the VORTEX2 project. In the velocity image on the left, Blues/green represent winds moving towards the radar, and reds/yellows indicate winds moving away from the radar. In the reflectivity image on the right, the main body of the storm can be seen, with the appendage on the bottom of the storm being a hook echo.