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Radar Facts
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Typical Hook Pattern
Figure 5-42
The hooks are located at the right rear side of the thunderstorm echo’s
direction of movement (usually the southwest quadrant).
The hook is not the tornado echo! A small scale low pressure area is
centered at the right rear side of the thunderstorm echo near its edge.
The low usually ranges from about 3 to 10 miles in diameter.
Precipitation is drawn around the low’s cyclonic circulation to form the
characteristic hook shape. Tornadoes form within the low near hook.
AccordingtostatisticsfromtheNSSL,almost60percentofallobserved
hookechoeshavetornadoesassociatedwiththem.Atornadoisalways
suspected when a hook echo is seen.
A hook can form with no tornadoes and vice versa. However, when a
bona fide hook is observed on a weather radar, moderate or greater
turbulence,strongshifting surfacewinds, andhail areoften nearbyand
aircraft should avoid them.
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