I recently got an email from a Jane in Pt. Pleasant and she asks: "What is a hook echo and how is it considered severe in weather?"
Good question Jane and thanks for reading my weather blog!
Here's the answer and some radar images to illustrate what a hook echo is.
The hook echo is one of the classic hallmarks of a tornado producing thunderstorm as seen on weather radar. The echo (name given to precipitation areas on radar) is produced by rain, hail or even debris being wrapped around the tornado. The National Weather Service considers the presence of a hook echo as sufficient to justify issuing a tornado warning.
Below is a Doppler radar image from the National Weather Service in Dodge City, Kansas of a thunderstorm producing a tornado. The twister is located in the hook or in the southwest part of the storm.
Rarely is a signature this classic or this obvious. At the left side of this image (above), a tornado was crossing interstate 44 south of Oklahoma City moving towards the town of Moore, OK where an F5 tornado hit! This F5 tornado (the strongest and rarest of all twisters) had winds of up 318 mph! That wind speed, which was detected by Doppler radar was the strongest wind speed ever recorded in history on Earth.
The bright red colors at the tornado location represent not hail or rain, but the aggregate signature of car parts, pieces of houses, shredded tree branches, dirt and other debris, hoisted thousands of feet skyward by the vortex. There also known as debris balls.
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