Interesting Weather Information

Thursday, May 25, 2017

The "Duck Test" in Meteorology

So what does James Whitcomb Riley, the great poet and author from Indiana have to do with the storms of March 24, 2017?

Riley, known as the "Hoosier Poet" and the "Children's Poet" is also credited with the following witticism, “When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck.”

Thus was born the "Duck Test", finding the simplest explanation for something you observe. Unfortunately the Duck Test often fails for complex systems like clouds associated with thunderstorms.

Let's re-phrase Riley's saying, When I see a cloud that moves like a tornado, touches the ground like a tornado and comes from a thunderstorm like a tornado, I call that cloud a tornado.

The problem is ... is that there are many low clouds that at first glance look like a tornado.


Take a look at this photo from NOAA.

This is a rain shaft, an intense downpour from a thunderstorm in the Great Plains. We see rain shafts here too. Take a look at these 3 photos from FOX19 Viewers.

Mary Campbell - Rain Shaft

Kelly Sears - Rain Shaft

Photographer Not Known - Rain Shaft

 Notice there are no horizontal striations or other indications of rotation. Rain shafts are often reported as tornadoes but they do not rotate and are not tornadoes.


How about this photo?
Scud clouds - Courtesy Washington Post.

Nope, not a tornado. It looks like one but there is no rotation, these are scud clouds.

Scud clouds can be very tornado-like. Clouds material gets caught up in the turbulence and down draft of a thunderstorm and can masquerade as a tornado.
 Here are three more scud cloud photos:




This one was taken by FOX19 NOW viewer Kathleen Niece in Glencoe, KY.

Photo by: Kathleen Niece


This is a scary looking thunderstorm, but there is not a tornado here. The wall cloud is large and low and wall clouds can partially descend to the ground.

Now take a look at these photos, sent to my by viewer Shannon Cross from Warren Co. last evening (WED may 24, 2017). She saved them from the Facebook pages of people in the area around Franklin and Carlisle, OH in Warren Co. and wanted to know if this was a big tornado like some people claimed.

The answer is, "NO", these pictures, of the same storm, do not show a tornado.


  • 1 The rotation as shown on radar was very weak.
  • 2. There are no - zero - damage reports
  • 3. The photographs show us this is not a tornado
  • Photo A  - No rotation evident, ragged edge like scud
  • Photo B - Still no rotation evident, dark back side looks interesting
  • Photo C -  A better look at the back side - the descending cloud formation is hollow
  • Photo D - The air is descending at the back of the cloud, not rising like in a tornado - look at the curl!

Weird clouds like these arise from the interplay of warm moist air flowing up and into the storm and cool, drier air sinking and flowing out of the storm.

Take a look at this amazing cloud  photograph taken by Stephanie West in Hebron, KY on June 15, 2012.

This is a shelf cloud and it forms from the interplay of inflow and out flow as shown in the second version of her photograph. The cool outflow is more dense and the warm, moist inflow rises op and over it. Beneath the warm air clouds descend in the sinking air.

To show how different one cloud can look from different directions, here is the same cloud, at the same time from in front of it near CVG.

Now ... imagine tilting the top photograph - left side up - and it does not take much imagination to get to what was seen in Warren Co.

So ...
It does not move like a tornado (no rotation).
It does not touch the ground like a tornado (no debris and no damage).
It does not come from a thunderstorm like a tornado (descending air not rising.

So it is not a duck. Oops! I mean it is not a tornado. It is a formation of scud clouds.

Thank you James Whitcomb Riley

Steve Horstmeyer